Infection as a potential trigger in glial fibrillary acidic protein astrocytopathy: a case report and review of immunotherapeutic strategies

Abstract

Purpose

Glial fibrillary acidic protein astrocytopathy (GFAP-A) is a form of autoimmune encephalitis (AE) that commonly affects the central nervous system (CNS). The pathogenesis of GFAP-A remains unclear, with infection proposed as a potential trigger, often leading to a misdiagnosis as meningoencephalitis due to overlapping clinical manifestations. This study aims to reports a case of GFAP-A associated with Enterococcus faecium infection, summarize the clinical characteristics, treatment details, and prognostic outcomes of GFAP-IgG-positive patients with concurrent infections, and provide evidence for optimizing clinical diagnosis and treatment strategies.

Methods

We report a detailed case of an 81-year-old male GFAP-A patient with an E. faecium infection, with primary manifestations of drowsiness and seizures. We also retrospectively analyzed 4 additional GFAP-A patients with confirmed infections from our institution (2022–2024) and systematically reviewed 20 eligible cases from the literature (2016–2024). The inclusion criteria were: (1) GFAP-IgG positivity in CSF/ serum, (2) definitive evidence of infection, (3) complete clinical, imaging, treatment, prognostic and laboratory data available.

Results

A total of 25 patients (19 males, 6 females; median age 45 years, range 12–81 years) were included. The most common initial symptoms were fever (80%, 20/25) and headache (76%, 19/25), followed by altered consciousness (76%, 19/25), urinary dysfunction (68%, 17/25), weakness (56%, 14/25), ataxia (44%, 11/25), blurred vision (40%,10/25), neuropsychiatric abnormalities (40%, 10/25), seizures (36%, 9/25), respiratory dysfunction (32%, 8/25), and positive meningeal signs (8%, 2/25). Brain MRI was abnormal in 75% (18/24) of patients, with T2-FLAIR hyperintensity (42%, 10/24) being the most common finding, and classic periventricular enhancement in 12.5% (3/24). All patients were GFAP-IgG-positive in CSF, and 52% (13/25) were positive in serum. Treatment included anti-infective therapy (all 25 cases) plus immunotherapy (21/25 cases: intravenous immunoglobulin (IVIG) in 16, corticosteroids in 12, plasma exchange (PE) in 4, protein A immunoadsorption (PAIA) in 1). Prognostic outcomes: 10 patients (40%) achieved complete recovery, 11 (44%) had residual sequelae (urinary dysfunction in 5, cognitive impairment in 3, motor weakness in 2, behavioral abnormalities in 1), and 4 (16%) had unknown prognosis. The index case showed significant recovery after combined anti-infective (piperacillin-tazobactam + linezolid) and IVIG, with modified Rankin Scale (mRS) score improving from 5 to 2 at 1-month follow-up.

Conclusion

Infection is a potential trigger for GFAP-A, and differentiation from infectious meningoencephalitis is challenging. For patients presenting with meningoencephalitis accompanied by persistent disturbances of consciousness and seizures, GFAP reactive antibody testing of CSF and plasma is appropriate. In patients with GFAP-A, early and effective anti-infective and immunotherapies may help to prevent disease progression and improve the likelihood of full recovery. In severe cases, additional immunotherapies may be required.

Introduction

Background

Glial fibrillary acidic protein astrocytopathy (GFAP-A) is a recognized autoimmune encephalitis (AE) that affects the central nervous system (CNS) and is often misdiagnosed as infectious meningoencephalitis due to overlapping clinical features [1–3]. Though relatively rare in clinical practice, it is increasingly recognized that identification of glial fibrillary acidic protein immunoglobulin G (GFAP-IgG) is a specific biomarker for the diseases in serum or cerebrospinal fluid (CSF), with the first reported in 2016 [4–6]. GFAP-A typically presents with acute or subacute onset, affecting the meninges, brain parenchyma, spinal cord, optic nerve, and peripheral nerves [3, 7, 8]. A hallmark finding by magnetic resonance imaging (MRI) is radial gadolinium enhancement along linear cerebral vessels, within the white matter, and perpendicular to the ventricles. However, lesions may also appear in the subcortical white matter, basal ganglia, hypothalamus, brainstem, cerebellum, and spinal cord [2, 3, 9].

Despite increasing recognition of GFAP-A, its pathogenesis remains poorly understood. Some reports suggest a potential link between GFAP-A and infections, although the specific pathogen(s) and underlying mechanisms are not well characterized, requiring further investigation [10–13]. While most GFAP-A patients respond favorably to immunotherapy, including corticosteroids and intravenous immunoglobulin (IVIG), a subset of patients exhibit poor therapeutic responses, with some cases resulting in relapse or death [14].

Objective

Given the diagnostic challenges and limited data on infection-associated GFAP-A, this study aims to: (1) Report a detailed case of GFAP-A associated with E. faecium infection; (2) Integrate clinical data from 4 additional institutional cases and 20 literature cases to summarize the clinical characteristics, treatment patterns, and prognosis of infection-associated GFAP-A; (3) Provide evidence for improving early diagnosis and individualized treatment strategies.

Materials and methods

This study included two parts: a case report of an index patient, and a combined analysis of institutional and literature cases. Institutional cases were retrospectively collected from the medical record system of The First Affiliated Hospital of Ningbo University (2022–2024) with the following criteria: (1) GFAP-A diagnosis; (2) Positive GFAP-IgG in CSF; (3) Definitive infection evidence (positive culture, mNGS, or pathogen-specific tests); (4) Complete clinical, imaging, laboratory, treatment, and follow-up data.

Because GFAP is a cytosolic intermediate filament protein of astrocytes, methods for detection of reactive antibodies are limited. Currently, we test for GFAP reactive antibody by immunofluorescence (IF)-cell-based assays (CBA), and western blot. CBA is the primary method [2]. In this study, the detection of GFAP-IgG and GFAP-IgM antibodies was conducted by IF using a commercially available CBA kit (Hangzhou Zhenyuan Biomedical Technology Co., Ltd., Zhejiang, China). The detection principle of this kit is based on the indirect immunofluorescence assay. The GFAP autoantibody present in the sample specifically binds to the overexpressed antigen (which is labeled with the mCherry fluorescent protein, emitting red fluorescence) on the cells within the kit, forming an antigen-antibody complex. Fluorescence microscopy is then employed to determine whether there is colocalization of red and green fluorescence signals. The presence of colocalized fluorescence indicates that the sample contains the specific antibody, whereas the absence suggests that the corresponding antibody is not present. Positive samples are subsequently subjected to titer determination. A positive result was defined by the presence of specific astrocytic staining accompanied by a CSF titer of at least 1:10 or a serum titer of no less than 1:32.

Blood cultures were conducted at two stages: Pre-transfer to our hospital, the patient had blood cultures at a local hospital (later confirmed positive for Enterococcus faecium, result pending on admission); Post-transfer to our Neurology Department, repeat blood cultures were negative. Blood cultures were not collected at initial ICU admission due to family refusal.

CNS autoimmune antibodies (AQP4, NMDAR, AMPAR1, AMPAR2, GAD65, MOG, mGluR5, LGI1, CASPR2, GABABR) were tested, and all results were negative. Oligoclonal bands in CSF were negative. Tests for tuberculosis, HSV, VZV, and EBV in CSF were negative. Urine culture was negative.

Literature review

On September 9, 2024, a systematic search of the PubMed database was conducted using a combination of the following search terms: bacteria, virus, infection, mycobacterium tuberculosis, autoimmune glial fibrillary acidic protein astrocytopathy, GFAP-IgG, GFAP-IgM, GFAP antibody, and GFAP autoimmunity. The search was further refined by including terms such as “clinical cases” and “case reports”, along with variations of the key terms. Only articles published in English and peer-reviewed journals were included in the review, with a time period from 2016 to 2024. After removing duplicate entries, titles and abstracts were independently screened, followed by a full-text review to identify relevant papers. Additionally, a manual review of the reference lists in the retrieved articles was performed to ensure no pertinent studies were overlooked during the initial search (Fig.1).

Fig. 1.

PRISMA flowchart

The inclusion criteria for cases were as follows: clear evidence of bacterial infection or viral sequences in the CSF (demonstrated by positive CSF culture or the detection of pathogen sequences through metagenomic next-generation sequencing (mNGS) of CSF), as well as the presence of GFAP reactive antibodies in CSF and/or serum. A total of 73 cases were identified as positive for GFAP reactive antibodies associated with infections, such as flu, HIV, dengue fever, HSV, EBV, and bacterial infections [2, 3, 10–18]. Of these, 20 patients had definitive evidence of infection, with comprehensive clinical data available.

PRISMA flowchart.

Case presentation

An 81-year-old male patient presented with a nine days history of altered consciousness and unresponsiveness, accompanied by intermittent limb convulsions, lasting approximately 10 min. The patient lived alone; no family member observed or reported mild pre-onset symptoms (e.g., low-grade fever, fatigue, or headache) before his sudden loss of consciousness. Three days prior to admission, the patient developed a high-grade fever (39.2℃) with chills and was evaluated at a local hospital’s emergency department. Initial clinical evaluation revealed hypotension (85/50mmHg), tachycardia (125 bpm), elevated inflammatory markers (C-reactive protein 185 mg/L, procalcitonin 8.5ng/ml), lactic acidosis (lactate 4.8mmol/L), hypokalemia (2.8mmol/L), and hyponatremia (128mmol/L), raising concerns for septic shock. Blood culture was pending at the time of transfer. Despite receiving comprehensive symptomatic treatment, including anti-infective therapy (piperacillin-tazobactam), anti-shock measures, anti-epileptic medication (sodium valproate solution), and correction of electrolyte imbalance, the patient’s condition remained unstable. Due to the perceived ineffectiveness of the treatment, the family opted to transfer the patient to our hospital’s Intensive Care Unit (ICU) for further management.

On admission to the ICU, the patient had a body temperature of 37.6 °C, a blood pressure of 97/64 mmHg, maintained with methoxamine, and oxygen saturation of 98–100% with nasal oxygen supplementation. This patient had a modified Rankin Scale (mRS) score of 5. The patient appeared lethargic, with diminished respiratory sounds and dullness on percussion in both lungs. A chest computed tomography (CT) scan showed moderate bilateral pleural effusions, hypo-inflation of both lungs, and mild pulmonary inflammation. Laboratory investigations revealed elevated inflammatory markers and electrolyte disturbances. Initial treatment included piperacillin-tazobactam for infection control, along with bromohexine to assist with mucus clearance, lacoxamide injection was anti-epilepsy, and other measures to correct water-electrolyte imbalance.

Cerebrospinal fluid (CSF) examination after lumbar puncture showed a white blood cell count of 18 /µL, lymphocyte ratio 14%, glucose 2.25mmol/L, lactate dehydrogenase 158 U/L, chloride 133.6 mmol/L, and protein 4931 mg/L. White blood cell count, lactate dehydrogenase, chloride and albumin increased, while the percentage of lymphocytes and glucose decreased. CSF culture confirmed an Enterococcus faecium infection (sequence 720, but contamination could not be ruled out). To rule out other autoimmune and infectious etiologies, comprehensive testing was performed. The patient was negative for AQP4, NMDAR, AMPAR1, AMPAR2, GAD65, MOG, mGluR5, LGI1, CASPR2, GABABR antibodies in both CSF and serum. Oligoclonal bands were absent. CSF PCR and mNGS were negative for herpes simplex virus (HSV), varicella-zoster virus (VZV), Epstein-Barr virus (EBV), and Mycobacterium tuberculosis. After contacting the patient’s family, we obtained the pending blood culture result from the external hospital, which was positive for Enterococcus faecium. Based on these findings, the patient was treated with piperacillin-tazobactam combined with linezolid for infection control, along with supportive therapies including potassium supplementation, fluid resuscitation, acid suppression, gastric protection, liver support, seizure prophylaxis (lacoxamide injection), anticoagulation, and albumin replacement. After five days of treatment, the patient still experienced occasional low-grade fever and lethargy. He was transferred to the neurology department for further evaluation. To monitor treatment response, we repeated blood culture, and the result was negative. At this point, the patient’s vital signs were stable, though a positive Babinski sign was noted on the right side. The patient had a mRS score of 4.

To investigate the etiology of the patient’s altered mental status and seizures, additional diagnostic tests were performed including enhanced brain MRI, as well as CSF and serum autoimmune antibody analysis. Brain MRI revealed a mildly increased signal in the pons by diffusion-weighted imaging (DWI), along with small patchy signal abnormalities in the lateral ventricles (Fig. 2). Serum testing detected GFAP-IgM antibodies at a titer of 1:32. Repeat lumbar puncture revealed yellowish CSF with positive GFAP-IgG antibodies at a titer of 1:10 (Table 1; Fig. 3). Based on these clinical, laboratory, and imaging findings, the patient was diagnosed with GFAP-A.

Fig. 2.

MRI A: Fluid Attenuated Inversion Recovery (FLAIR); B: Apparent Diffusion Coefficient (ADC); C: Gadolinium-enhancement T1-Weighted imaging (T1WI); D: Sagittal T2-Weighted. DWI demonstrated a slightly high signal shadow within the pons, while the ADC map presented a slightly low signal shadow. A few small patchy iso-intense T1 and T2 signal shadows were observed in the lateral ventricle, with blurred edges. The signal of the remaining brain parenchyma remained unaltered, and the boundary between the gray and white matter was distinct. The enhanced scan did not reveal any obvious abnormal signal shadow. There was no sign of a mass in the suprasellar cistern and bilateral CPA. The midline structure of the brain was centered, and the ventricles, cisterns, sulci, and fissures of the brain were enlarged and deepened

Table 1.

CSF examinations of the patient

Time	OP (mmHg)	CSF WBC (/µL)	CSF Pro (mg/L)	CSF Glu (mmol/L)	CSF Chlo (mmol/L)	Serum Glu (mmol/L)	Other tests
Day 2 after admission	80	18↑	4931↑	2.25↓	133.6↑	5.1	mNGs: enterococcus faecium (sequence 720)
Day 11 after admission	70	2	3387↑	2.35↓	125.2	4.7	GFAP antibody 1:10 (CSF), 1:32 (serum)

OP opening pressure, Pro protein, Glu glucose, Chlo chloride, ADA mNGS: metagenomic next-generation sequencing; GFAP: glial fibrillary acidic protein

*CNS autoimmune antibodies comprise markers for AQP4, NMDAR, AMPAR1, AMPAR2, GAD65, MOG, mGluR5, LGI1, CASPR2, GABABR, and GFAP. All the results were negative except GFAP. CSF oligoclonal bands were negative

Fig. 3.

GFAP GFAP-IgG was detected using the GFAP-IgG detection kit (immunofluorescence assay, CBA). A1-A3/B1-B3: Cerebrospinal fluid/serum samples from patients showed. A1/B1: GFAP antibody binding in patients (green), A2/B2: GFAP antigen (red, with mCherry fluorescent protein), A3/B3: co-localization was confirmed by the combined images (white arrows), which was a positive result. C1-C3: negative control. C1: there were no green fluorescent cells in the green fluorescence channel and no GFAP antibody, C2: Red fluorescence (GFAP antigen), C3: No co-localization (only red fluorescence). (scale bar = 10μm)

The patient was subsequently treated with intravenous IVIG at 25 g/day for five days to modulate the immune response, as well as continued anti-epileptic therapy (sodium valproate tablets), anti-infective treatment, and fluid resuscitation. Following treatment, the patient regained consciousness, exhibited improved respiratory function, and became capable of semi-independent self-care. The patient had a mRS score of 3. At one-month follow-up post-discharge, the patient was able to walk independently and care for himself, with a favorable recovery. The patient had a mRS score of 2(Fig. 4). Both the patient and the doctor believed that recovery was very good. The patient could walk slowly by himself, and was able to take a walk, take a bath, wash, and eat, with only occasional help from his family. Currently, the patient is satisfied with his recovery, and very grateful for the care of the medical staffs. We will continue to follow this patient’s recovery.

Fig. 4.

Clinical course and of patient. D3: CSF mNGs indicated Enterococcus Faecium infection, so linezolid was added as an anti-infective treatment. D9: Serum GFAP-IgG was positive (1:32). D12: CSF GFAP antibodies were detected. D12: CSF GFAP-IgG indicated positive (1:10). D13: Considering that the patient was more likely to be diagnosed with GFAP-A, IVIG (25g) was initiated. D18: the patient’s basic symptoms had recovered, so he was discharged

Results

We described a detailed case of an 81-year-old male GFAP-A patient with E. faecium infection, and also retrospectively analyzed 4 additional GFAP-A patients with confirmed infections from our institution (2022–2024) and systematically reviewed 20 eligible cases from the literature (2016–2024), in Table 2.

Table 2.

Clinical data for patients with GFAP-IgG or GFAP-IgM and infection

Number	Authors and year	Pathogen	Age, sex	Onset symptoms	Symptoms after initial treatment	CSF findings	GFAP-IgG CSF/serum	MRI	Main treatment	Prognosis
1	Li et al. 2023 doi: 10.1186/s12883-023-03113-w[10]	TB, Legionella pneumophila	45, M	Fever, cough, headache	Disturbance of consciousness, decreased neck resistance, and a positive bilateral Kerr’s sign	CSF pressure was 330 mmH2O, pleocytosis, increased protein, decreased glucose, decreased chloride, increased ADA Mycobacterium tuberculosis as the pathogenic microorganism	+ / +	Punctate infarcts in the right cerebellar hemispheres and temporal lobe and multiple lesions in the right insula, left thalamus and around the cistern. Some of the nodules were enhanced after injection of gadolinium	Antitubercular agent, antibiotic, IVMP	All symptoms improved
2	He et al. 2022 doi: 10.3389/fimmu.2022.950522[11]	Brucella	42, M	Fever, headache	Bilateral lower extremity numbness and weakness, difficulty urinating, ataxia	Pleocytosis	+ / -	Normal	Antibiotic, PE, IVIG, IVMP	All symptoms improved
3	Wang et al. 2024 doi: 10.1186/s40001-024-01926-0[13]	EBV, Pseudomonas aeruginosa, Candida, Enterococcus faecalis	Middle-aged, M	Fever, headache	Consciousness disturbance, refractory central hypoventilation, urinary dysfunction	CSF pressure > 500 mmH2O, pleocytosis, increased proteins, normal glucose and chloride	+ / +	Multiple patchy T2-weighted FLAIR hyperintensities in bilateral frontal, parietal, basal ganglia regions, as well as adjacent to the lateral ventricles.	PAIA, antivirus, antibiotic, mechanical ventilation support	Respiratory function improved and urinary dysfunction after 1 month, all symptoms improved after 6 months
4	Handoko, et al. 2019 doi: 10.1016/j.pediatrneurol.2019.05.010[18]	HSV	12, M	Headache, fever, vomiting	decreased responsiveness, seizures	Unknown	+ / -	Normal	Antiviral therapy, rehabilitation therapy, immunotherapy	Increasing memory deficits, impulsivity, and behavior problems over the next months
5	Lan et al. 2023 doi: 10.1007/s13760-023-02268-0[12]	Streptococcus intermedius	58, M	Dizziness, headache	Ataxia, impaired consciousness, extremity weakness, blurred vision	Normal	+ / +	(1) Re-examination of brain abscess: significant shrinkage of enhanced lesions in the right parietal and occipital regions and the surrounding edema and a smaller space-occupying effect compared to the previous examination; (2) Same brain stem signal abnormalities as before, the possibility of ischemic foci or demyelinating lesions should be considered	Antibiotic	All symptoms improved
6	Lan et al. 2023 doi: 10.1007/s13760-023-02268-0[12]	Borrelia burgdorferi	52, M	Fever	Headache, tremor, urinary dysfunction, bowel dysfunction, ataxia, neck resistance, extremity weakness, blurred vision, numbness in the ends of extremities	Pleocytosis, increased protein, decreased chloride and glucose	+ / +	Normal	Antibiotic, immunoglobulin	All symptoms improved
7	Li et al. 2018 doi:10.1016/j.msard.2018.02.020[19]	HSV	35, F	Subacute headache, vomit, fever	Seizure, psychiatric / behavioral abnormalities	Unknown	+ / +	diffuse and extensive T2/FLAIR hypersignal in the bilateral temporal lobe	Antiviral therapy, IVIG	The symptoms were relieved and the patients were followed up continuously
8	Wang et al. 2022 doi:  10.1097/MD.0000000000031995[20]	EBV	37, M	Fever, headache	Urinary dysfunction	Pleocytosis	+ / Not mentioned	T2- and FLAIR-hyperintense in cortex and white matter in both cerebral hemispheres; enhanced and patchy signals in C2–5 cervical spine; meninges enhancement	Antivirus, IVIG	All symptoms improved
9	Lan et al. 2023 doi: 10.1097/MD.0000000000031995[20]	EBV	14, M	Fever, headache, extremity tremor	Urinary dysfunction, bowel dysfunction, ataxia, psychiatric abnormalities, impaired consciousness, convulsion, extremity weakness, blurred vision	Pleocytosis, increased protein, decreased chloride	+ / +	Linear perivascular radial enhancement; hippocampal, thalamic, and midbrain abnormal hyperintensity on FLAIR; enhancement in the cervical spinal cord and spinal meninges	Antivirus, antibiotic, IVIG, IVMP	Detrusor muscle dysfunction and paresthesia remaining after 6 months
10	Lan et al. 2023 doi: 10.1007/s13760-023-02268-0[12]	EBV	86, M	Headache, numbness	Urinary dysfunction, bowel dysfunction, ataxia, psychiatric abnormalities, impaired consciousness, convulsion, extremity weakness, blurred vision	Pleocytosis, increased protein, decreased chloride	+ / +	Did not complete	Antivirus, antibiotic, IVIG, steroids	Quadriparesis, prolonged bed confinement, ongoing, tracheostomy dependency after 6 months
11	Lan et al. 2023 doi: 10.1007/s13760-023-02268-0[12]	EBV	65, M	Fever, headache, limb weakness	Urinary dysfunction, bowel dysfunction, extremity weakness, blurred vision	Increased protein, decreased chloride	+ / +	Normal	Antiviral, antibiotic	All symptoms improved
12	Lan et al. 2023 doi: 10.1007/s13760-023-02268-0[12]	EBV	27, M	Fever, abnormal pain, vomiting	Urinary dysfunction, bowel dysfunction, ataxia, psychiatric abnormalities, impaired consciousness, extremity weakness, blurred vision	Pleocytosis, increased protein, decreased chloride	+ / +	Normal	Antibiotic	All symptoms improved
13	Lan et al. 2023 doi: 10.1007/s13760-023-02268-0[12]	EBV	14, F	Fever, headache	Urinary dysfunction, bowel dysfunction, ataxia, psychiatric abnormalities, impaired consciousness, convulsion, extremity weakness, blurred vision	Pleocytosis, increased protein, decreased chloride and glucose	±	Slight thickening of bilateral pia mater; suspicious MERS	Antiviral, antibiotic, IVIG, steroids	All symptoms improved
14	Lan et al. 2023 doi: 10.1007/s13760-023-02268-0[12]	EBV, TB	47, F	Fever, headache, altered consciousness	Urinary dysfunction, bowel dysfunction, ataxia, psychiatric abnormalities, impaired consciousness, convulsion, extremity weakness, blurred vision	Pleocytosis, increased protein, decreased chloride and glucose	±	Multiple abnormal-signal nodules in right occipital lobe, corona radiata, and cerebellar hemisphere	Antibiotic, antiviral, antitubercular agent	All symptoms improved
15	Lan et al. 2023 doi: 10.1007/s13760-023-02268-0[12]	EBV	50, M	Fever, headache	Urinary dysfunction, bowel dysfunction, ataxia, psychiatric abnormalities, impaired consciousness, convulsion, extremity weakness, blurred vision	Pleocytosis, increased protein, decreased chloride	+ / +	Normal	Antiviral, antibiotic, dexamethasone	Urinary dysfunction and lower limb fatigue remaining after 6 months
16	Lan et al. 2023 doi: 10.1007/s13760-023-02268-0[12]	EBV	65, M	Fever, headache, psychiatric abnormalities	Urinary dysfunction, bowel dysfunction, ataxia, psychiatric abnormalities, impaired consciousness, convulsion, extremity weakness, blurred vision	Pleocytosis, increased protein, decreased chloride	+ / +	Signal abnormalities in the splenium of the corpus callosum	Antibiotic, Antiviral, antitubercular agent, low-dose hormone, IVIG	All symptoms improved
17	Lan et al. 2023 doi: 10.1007/s13760-023-02268-0[12]	EBV	30, M	Fever, headache	Urinary dysfunction, bowel dysfunction, ataxia, psychiatric abnormalities, impaired consciousness, convulsion, extremity weakness, blurred vision	Pleocytosis, increased protein, decreased chloride	±	Signal abnormalities in the splenium of the corpus callosum and thoracic spinal cord	Antibiotic, antiviral, low-dose hormone, IVIG	All symptoms improved
18	Zhang et al. 2023 doi: 10.1016/j.jneuroim.2023.578174[14]	EBV	59, M	Fever, tremor	Urinary dysfunction, coma, dyspnea, lower limbs weakness	Pleocytosis, increased protein	+ / +	FLAIR and T2-hyperintense lesions in the white matter of bilateral cerebral hemispheres, bilateral basal ganglia and cerebellum	Antiviral, IVMP, IVIG	Neurogenic bladder after 6 months
19	Zhang et al. 2023 doi: 10.1016/j.jneuroim.2023.578174[14]	EBV	54, M	Fever, tremor, urinary dysfunction, altered consciousness	Coma, dyspnea, paralysis of lower limbs and hypoesthesia below T10 level	Pleocytosis, increased protein	±	T2-weighted and FLAIR linear perivascular radial gadolinium; mild T2-FLAIR hyperintense signal around left corona radiate, the lateral ventricle and basal ganglia, with no significant enhancement; multiple spondylitis of anterior corners	Antiviral, IVMP, IVIG	Urinary incontinence after one year
20	Zhang et al. 2023 doi: 10.1016/j.jneuroim.2023.578174[14]	EBV	62, M	Fever, headache, tremor, urinary dysfunction	Coma, gastrointestinal hemorrhage	Pleocytosis, increased protein	+ / +	Patchy T2- and FLAIR-hyperintense signal in left frontal lobe	Antiviral, IVMP, IVIG	Deceased one month after disease onset
21	None	Enterococcus faecium	81, M	Primary manifestations of drowsiness, seizures, fever	Unconsciousness	CSF pressure was 80 mmH2O, pleocytosis, increased protein, decreased glucose, Enterococcus faecium as the pathogenic microorganism	+ / +	A mildly increased signal in the pons by DWI, along with small patchy signal abnormalities in the lateral ventricles	Antibiotic, IVIG	All symptoms improved
22	None	TB	55, M	Weakness	None	Pleocytosis, increased protein, decreased glucose	+ / -	Multiple rounds, patchy long T2 and slightly long T1 signal foci can be seen around the lateral ventricles and in the white matter of the hemioval region, with poorly defined boundaries. T2-flair shows high signal, some of them show ring sign, and some of them show mild ring and nodular enhancement	Anti-tuberculosis, hormone pulse therapy	All symptoms improved
23	None	Proteus mirabilis	66, F	Blurred vision	Blurred vision	Pleocytosis, increased protein, decreased glucose	+ / +	There were small patches of long T1 and long T2 signal shadows in the bilateral semioval area, large FLAIR hyperintensity shadows in the adjacent white matter area, and the edge was blurred. DWI showed equal or low signal, ADC showed slightly high signal, and no obvious abnormal enhancement was found after enhancement. There were a few patchy nodules and slightly long T2 signal shadows on T1 near the lateral ventricles on both sides, and the diffusion was not limited	Antibiotic, PE, IVIG, hormone pulse therapy	Blurred vision recurred repeatedly
24	None	Human herpesvirus, TB	39, F	Fever, unconsciousness	Unconsciousness	Pleocytosis, increased protein, decreased glucose, increased lactate dehydrogenase	+ / +	Bilateral thalamus and basal ganglia showed small patches of slightly long T2 signal, T2-FLAIR showed slightly high signal; Multiple T2-flair slightly hyperintense signals were also seen in the cerebral cortex on both sides	Antibiotics, antiviral, anti-tuberculosis, plasma exchange, hormone immunotherapy	All symptoms improved
25	None	TB	37, M	Urinary dysfunction, fatigue, respiratory failure, altered consciousness	Urinary dysfunction, unconsciousness	Pleocytosis, increased protein, decreased glucose, increased lactate dehydrogenase	+ / -	Abnormal signal foci were scattered in the cervical spinal cord of C2-7.	Anti-tuberculosis, hormone pulse therapy	Critically ill, the patient was transferred for treatment, and the prognosis was unknown

CSF cerebrospinal fluid, GFAP glial fibrillary acidic protein, MRI magnetic resonance imaging, FLAIR fluid-attenuated inversion recovery, IVMP intravenous methylprednisolone, IVIG intravenous immunoglobulins, PE plasma exchange, PAIA Protein A immunoadsorption, EBV Epstein–Barr virus, TB tuberculosis, HSV herpes simplex virus

25 patients (19 males and 6 females, median age 45 years, range 12–81 years) had both reactive GFAP antibody and pathogen infection. Fever (80%) and headache (76%) were the most common initial symptoms, followed by a range of other clinical manifestations, including dysuria (68%) and altered consciousness (76%). Previous studies, including a Japanese study, have shown that more than half of GFAP-A patients exhibit autonomic nervous system dysfunction, with urinary dysfunction being a common feature [8]. This suggests that autonomic nervous system involvement is common among patients positive for GFAP reactive antibodies. However, it is important to note that autonomic dysfunction typically does not present as an early symptom and thus requires careful clinical observation. Other symptoms included weakness (56%), blurred vision (40%), neuropsychiatric abnormalities (40%), ataxia (44%), seizures (36%), positive meningeal signs (8%), and respiratory dysfunction (32%).

24 patients underwent MRI examination, of which 18 (75%) showed abnormal findings. Lesions in various regions of the brain were observed, including the cerebral hemispheres, basal ganglia, corpus callosum, brainstem, and spinal cord. 3 patients (12.5%) showed typical periventricular enhancement, while 10 patients (42%) showed T2-FLAIR hyper-intensity. Previous studies have found T2-FLAIR hyper-intensity to be more common in GFAP-A patient than typical periventricular enhancement [4, 8]. In a 2016 study by Flanagan et al., 17 out of 38 patients with GFAP-A exhibited linear perivascular radial gadolinium enhancement, while seven had normal image findings [9].

Interestingly, while MRI findings were normal in one patient, fluorodeoxyglucose positron emission tomography (FDG-PET) revealed abnormal FDG uptake primarily in the thoracolumbar segment of the spinal cord, with the hypermetabolic area localized near the T12 level. CSF analysis showed elevated white blood cell counts in all patients, with increased protein levels in three and decreased chloride and glucose levels in two patients. These observations are generally consistent with bacterial infections. GFAP reactive antibodies were detected in the CSF of all patients (100%), while serum GFAP reactive antibodies were positive in about half (52%). This finding underscores the higher diagnostic value of CSF GFAP reactive antibody testing, which is supported by previous studies [9].

All patients received anti-infective therapy. Of note, four patients recovered completely without corticosteroid or IVIG treatment. We speculate that patients who recovered without immunotherapy may have had lower CSF GFAP-IgG titers. Some patients had local infections, which may produce limited astrocyte damage and a mild immune response. With early antibiotic anti-infection treatment, patient infections are controlled quickly and immunotherapy is not needed. Such findings need to be explored further. One patient had urinary dysfunction after one month of protein A immuno-adsorption (PAIA) treatment, with symptom improvement after six months. Most patients improved after treatment, with no recurrence or aggravation observed during follow-up. Although the sample size was limited, the outcomes suggested an overall effectiveness of treatment. Previous studies have indicated that some GFAP-A patients can recover without long-term sequelae following immunotherapy, while others may relapse, with immunotherapy proving ineffective upon recurrence. Additionally, some patients experience poor outcomes, including death, underscoring the need for careful management [21, 22]. These findings highlight the importance of early diagnosis and tailored treatment strategies in GFAP-A patients. Clinicians must remain vigilant with their patients and continue to search for safer and more effective therapeutic approaches to manage this condition.

Discussion

This study reports a severe case of E. faecium-associated GFAP-A and summarizes 25 infection-associated GFAP-A cases (5 from our institution and 20 from literature). Key findings include: (1) Infection is a potential trigger for GFAP-A; (2) Fever (80%) and headache (76%) are the most common initial symptoms, with altered consciousness (76%) and urinary dysfunction (68%) frequently observed; (3) CSF GFAP-IgG is a highly sensitive diagnostic marker; (4) Combined anti-infective and immunotherapy improves outcomes, with IVIG being a safe option for septic patients. These findings, integrating our index case and pooled data, provide critical insights into the diagnosis, pathogenesis, and treatment of infection-associated GFAP-A.

GFAP-IgG in CSF is essential for diagnosis but is not a reliable biomarker. It has previously been shown that high concentrations of GFAP reactive antibodies can also be found in the serum of patients with Alzheimer’s disease and previous trauma. This suggests that instead of inducing pathological changes, the antibody may reflect an inflammatory process, indicating an association with immune cells [23]. This patient’s positivity for GFAP-IgG (CSF 1:10; serum 1:32) may suggest acute immune activation, stimulating an autoimmune response. Since cell-specific autoantigen IgG lacks pathogenicity for live target cells in vivo, such detection of autoimmunity in patients is helpful for diagnosis of autoimmune reactions occurring after bacterial infection [24]. Based on the clinical manifestations, CSF analysis, and positive GFAP-IgG, sufficient evidence was provided for the diagnosis of GFAP-A, so FDG-PET examination was not conducted. Notably, the low sequence count for E. faecium raises concerns about potential sample contamination, leaving a critical unanswered question: Was GFAP-A triggered by E. faecium-induced immune dysregulation, or did two distinct pathologies coincidentally exist? This ambiguity underscores the need for mechanistic exploration.

Currently, clinical understanding of GFAP-A remains limited, and there is no standardized diagnostic or treatment protocol. Combining 25 patients with infection-associated GFAP-A, we found that GFAP-A patients typically share several key features: (1) Acute or subacute onset, with clinical manifestations primarily involving meningoencephalitis, myelitis, or optic neuritis. (2) CSF analysis typically shows increased lymphocytes, elevated protein, and positive GFAP-IgG antibodies. Although GFAP reactive antibodies may also be present in serum, CSF antibodies are considered more diagnostically significant. (3) MRI often shows multiple intracranial or spinal lesions, with characteristic perivascular radial gadolinium enhancement perpendicular to the lateral ventricles. T2-weighted and FLAIR abnormalities are frequently observed. (4) Treatment with corticosteroids or IVIG is generally effective. (5) Patients may also present with other CNS autoimmune antibodies or concurrent tumors such as ovarian teratoma or nasopharyngeal carcinoma. Other diseases must be excluded, and diagnosis should be based on a comprehensive evaluation of clinical, imaging, and laboratory findings. Early diagnosis and timely initiation of immunotherapy and immunomodulatory treatments, particularly during the acute phase, are crucial for improving outcomes, reducing sequelae, and improving prognosis [4, 9, 14, 21, 25].

Although liner perivascular radial gadolinium enhancement by MRI is considered a hallmark of GFAP-A, it may be absent in up to half of cases [26], our patient did not see the typical GFAP-A effect changes in cranio-enhanced MRI. A 2016 study by Flanagan et al.. found that 17 out of 38 GFAP-A patients exhibited characteristic radial gadolinium enhancement, while seven had normal MRI findings [9]. T2-FLAIR hyper-intensities appear to be more common in GFAP-A patients than typical periventricular enhancement [16]. Additionally, Cheng et al. [27]. reported that these enhancement patterns may resolve as symptoms improve. The absence of linear radial enhancement but the presence of scattered patchy shadows on MRI raises the question: Did sodium and potassium correction during hospitalization contribute to demyelination, altering the MRI findings? A significant risk of demyelination exists following hyponatremia correction, even when the correction rate is within recommended limits [28]. In our results, only 3 of 24 (12.5%) patients had typical radial periventricular enhancement, while 10 of 24 (42%) presented with T2-FLAIR hyperintensity. Notably, 1 of 24 patients in the combined cohort had normal MRI but abnormal FDG-PET uptake in the spinal cord, further highlighting the limitations of radiological differentiation. These data emphasize that GFAP-IgG testing (especially in CSF) is indispensable for patients with meningoencephalitis and persistent neurological symptoms, regardless of MRI findings.

The apparent ‘fast’ autoimmune response is misleading. The patient’s living-alone status led to unrecognition of mild early infection symptoms, and the actual infection onset was likely 1–2 weeks before admission (earlier than the documented 9-day altered consciousness history). This timeline aligns with known mechanisms of infection-induced autoimmunity (molecular mimicry or bystander activation), which require 5–7 days for T/B cell activation and autoantibody production-ruling out a ‘rapid’ immune trigger.

The temporal sequence-where neurological symptoms persisted after infection control-strongly suggests that the E. faecium infection may have triggered an autoimmune response against GFAP. While the low pathogen sequence count necessitates cautious interpretation, it aligns with proposed mechanisms of infection-induced autoimmunity, which require a latency period for T/B cell activation and autoantibody production. The high frequency of EBV-associated GFAP-A may indicate a particularly strong trigger but could also reflect publication bias. The true spectrum of infectious precursors and their associated clinical phenotypes require further delineation through prospective, multi-center studies.

Reports of elevated GFAP reactive antibody levels, following bacterial infection, are rare. The mechanisms by which bacterial infections trigger GFAP-A remain under investigation. For instance, in cases of GFAP-A following Brucella infection, it is believed that bacterial infection triggers an autoimmune inflammatory response. Pathogen invasion disrupts cellular membranes, leading to the release of cytoplasmic contents, which can be misidentified by the immune system and cause neuronal damage [29]. In GFAP-A associated with bacterial infection, the proposed mechanisms include the following. (1) Potential direct interaction between bacteria and astrocytes or microglia, which may disrupt membranes and expose GFAP epitopes, particularly with certain intracellular. (2) Proinflammatory cytokine storms (IL-6, IL-1β, TNF-α) compromising blood-brain barrier integrity. (3) Pathogen-associated molecular patterns (PAMPs) activating Toll-like receptors to breach immune tolerance. (4) Infected B cells and exosomes carrying their expressed products enter the CNS and force CNS immune cell clearance (e.g., uptake by glial cells or elimination by T cells), thereby triggering local CNS inflammation leading to damage of nearby cells. This damage triggers T cell reactivity to CNS antigens released after injury (i.e., bystander injury) (Fig. 5) [6, 29–32]. Finally, it is important to note the speculative nature of some aspects of our mechanistic model. While Fig. 5 illustrates bacterial internalization by glial cells, the primary phagocytic role in the CNS is attributed to microglia. Direct evidence for astrocyte internalization of extracellular bacteria like E. faecium is limited, and this pathway may be more relevant to specific intracellular pathogens. The proposed model thus serves as a comprehensive hypothesis to guide future research.

Fig. 5.

Mechanism hypothesis(1) Bacteria are recognized by CNS resident immune cells (e.g., microglia) and may, in some cases, interact with or be internalized by astrocytes, particularly with certain intracellular pathogens. (2) Bacteria-activated astrocytes and microglia secrete IL-1β, TNF-α, IL-6, and CCL2. (3) TNF-α and IL-6 induce astrocyte apoptosis. (4) pro-inflammatory mediators disrupt BBB, activate endothelial cells, then release into the blood. (5) Activated BBB increase permeability to monocytes and neutrophils. (6) B cells infected with the pathogen secrete antibodies, which are taken up by glial cells or T cells, leading to local inflammation. (7) Immune cells expose GFAP epitopes in the glial cells, prompting the production of GFAP antibodies.

At the same time, extracellular bacteria, such as E. faecalis and Neisseria meningitidis, can survive and reproduce freely in serum. Therefore, the first necessary condition for their entry into the CSF is direct adhesion to the layer of cells forming the blood-CSF barrier, which can be facilitated through transcellular transport via endocytosis. Alternatively, this can occur through a paracellular pathway, which requires the disruption of tight junctions (Fig. 6A). Moreover, direct cytotoxic effects or bacteria-induced apoptosis may also allow free bacteria to enter the perivascular space. However, this mechanism is currently considered unlikely and is not widely recognized. Lastly, leukocytes can facilitate the transport of pathogens. But compared to intracellular pathogens that can invade mononuclear phagocytes and survive within their cytoplasm, extracellular bacteria are more resistant to phagocytosis. Thus, the likelihood is low that extracellular bacteria will cross the blood-CNS barrier via phagocytes and cause infection (Fig. 6B) [33]. Another study found that innate immune activation, triggered by invading pathogens at the onset of systemic infection, may facilitate bacterial adhesion and passage through the blood-CSF barrier. Innate immune system activation increases the expression of endothelial cell membrane ligands for bacterial adhesins, increasing permeability of the cell layer (Fig. 6C) [34]. Importantly, the core mechanisms (BBB disruption, epitope exposure, autoimmune activation) are shared across viral and bacterial triggers: regardless of pathogen type, infection initiates a cascade that leads to GFAP-directed autoimmunity. This universality ensures the mechanistic discussion is relevant to all infection-associated GFAP-A cases, not just bacterial ones.

Fig. 6.

Conjecture on the mechanism of bacteria entering CSFA: Extracellular bacteria are transported transcellular either by endocytosis or by opening tight junctions. Direct cytotoxic effects or bacteria-induced apoptosis may also allow free bacteria to enter the perivascular space. B: Leukocytes facilitate the transport of infected phagocytes. C: Innate immune activation triggered by invading pathogens at the onset of systemic infection may favor bacterial adhesion and crossing the blood-CSF barrier by increasing membrane ligand expression of bacterial adhesins on endothelial cells, or by increasing the permeability of the cell monolayer

Our data show that 84% of patients required immunotherapy in addition to anti-infective therapy, with 40% achieving complete recovery. Key treatment considerations: (1) Anti-infective therapy: Early targeted treatment is critical to control the trigger infection and reduce CNS inflammation. (2) Immunotherapy: IVIG is preferred in septic patients due to the risk of corticosteroids exacerbating infection. Corticosteroids or PE/PAIA can be used as rescue therapy for IVIG-refractory cases. (3) Supportive care: Anti-epileptic drugs and electrolyte correction are important for symptom control. Notably, 4 patients (16%) recovered with anti-infective therapy alone, possibly due to low GFAP-IgG titers and mild immune responses—this suggests that immunotherapy may not be necessary for mild cases with effective infection control.

This case offers vital lessons. (1) It is important to be vigilant for autoimmune etiologies in ‘treatment-refractory infectious encephalitis’. (2) Clinicians should rioritize CSF antibody testing in that GFAP-A’s radiologic findings are variable. (3) For treatment, IVIG should be favored over corticosteroids in septic situations due to the potential risk of exacerbating infection with corticosteroids in septic situations [18]. (4) Validated diagnostic algorithms should be implemented that differentiate GFAP-A from tuberculous meningitis, as proposed by Chen et al. [15]. Future research should employ multi-omics approaches to decipher infection-autoimmunity crosstalk and explore innovative therapies like CAR-T cells and microbiome modulations.

Limitations

There are limitations to this report. First, we acknowledge the potential for retrospective bias in this small sample size. However, we did include four GFAP-A patients seen in our hospital from 2022 to 2024, and in the future, we will continue to focus on such patients. In terms of method heterogeneity, all tests were performed by professional laboratories using commercial kits. Moreover, the CBA assay has high sensitivity and specificity, and can detect low titers of antibodies, which is helpful for early diagnosis and disease monitoring. The CBA method is used for semi-quantitative detection, and the antibody titer is judged by the change in fluorescence intensity, which is a helpful clinical assessment of the patient’s antibody titer with regard to disease course, therapeutic effects, and the risk of disease recurrence. At the same time, we also acknowledge that the CBA method has limitations, and the similar antibody components in the blood may cause cross reactions and cause false positive results, but the patient’s serum and CSF GFAP-IgG were positive. To exclude contamination, we searched CSF samples from March 1 to March 20, 2024 for mNGS analysis of the same laboratory batch. A total of 11 CSF mNGS samples were submitted for testing, and E. faecium was detected only in our patient, supporting the specificity of the finding in our patient.

Conclusion

Infection is a key potential trigger for GFAP-A, and differentiation from infectious meningoencephalitis is challenging. For patients with meningoencephalitis and persistent neurological symptoms (consciousness disturbance, seizures, urinary dysfunction), GFAP-IgG testing in CSF and serum is recommended. Early targeted anti-infective therapy combined with individualized immunotherapy (prioritizing IVIG in septic patients) can improve outcomes and reduce sequelae. Severe cases may require PE or PAIA as rescue therapy. Future prospective multi-center studies are needed to validate these findings and explore the long-term prognosis of infection-associated GFAP-A.

Abbreviations

GFAP-A

Glial fibrillary acidic protein astrocytopathy

CNS

Central nervous system

AE

Autoimmune encephalitis

IgG

Immunoglobulin G

GFAP

Glial fibrillary acidic protein

MRI

Magnetic resonance imaging

DWI

Diffusion-Weighted Imaging

ICU

Intensive care unit

CT

Computed tomography

CSF

Cerebrospinal fluid

FLAIR

Fluid-attenuation inversion recovery

IVMP

Intravenous methylprednisolone

IVIG

Intravenous immunoglobulins

PE

Plasma exchanges

TB

Tuberculosis

EBV

Epstein–Barr virus

FDG PET

Fluorodeoxyglucose positron emission tomography

PAIA

Protein A immunoadsorption

mNGs

Metagenomic next-generation sequencing

TNF-α

Tumor necrosis factor α

BBB

Blood-brain barrier

HSV

Herpes simplex virus

IF

Immunofluorescence

CBA

Cell-based assays

mRS

modified Rankin Scale

VZV

Varicella-zoster virus

Authors’ contributions

ZSQ: Investigation, Resources, Writing - Original Draft. WYJ: Investigation. LZ and WQY: Writing - Review & Editing, Funding acquisition. All authors reviewed the final manuscript.

Funding

This study was supported by the Key Scientific and Technological Projects of Ningbo (No. 2025Z162), and Zhejiang Province Traditional Chinese medicine science and technology project (No. 2025ZL117), and Zhejiang Yangtze River Delta Health Research Fund (2025CSJ5-A002), and Brain Health Youth Fund-Alzheimer's Disease Precision Diagnosis and Treatment Research (SMlDF-150-2025A27), and Ningbo Public Welfare Science and Technology Planning Project (2025S029).

Data availability

Not applicable.

Declarations

Ethics approval and consent to participate

This study was conducted in accordance with the Declaration of Helsinki (World Medical Association, 2013 revision).

Consent for publication

Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.

Competing interests

The authors declare no competing interests.