Diagnostic challenge of human herpesvirus 8-associated multicentric Castleman disease in a patient living with HIV disease

Summary

A man in his early 30s presented with a 4-month history of low-grade fever and chronic dry cough. Three months before admission, he developed persistent low-grade fever, rash and bilateral cervical lymphadenopathy. He was diagnosed with HIV infection and started on tenofovir/lamivudine/dolutegravir. Two weeks before admission, he developed right-sided pleuritic chest pain. Chest CT revealed bilateral pleural effusions and generalised lymphadenopathy involving the lower cervical, mediastinal and axillary regions. An excisional biopsy of a right lower cervical lymph node demonstrated hyaline-vascular architecture, including ‘lollipop’ lesions and onion-skinning of the mantle zones. Immunohistochemistry showed human herpesvirus 8 (HHV-8)-positive plasmacytoid cells within the mantle zones, without malignant features, consistent with HHV-8-associated multicentric Castleman disease (MCD). The patient continued antiretroviral therapy and received rituximab 375 mg/m² every week for four cycles. He achieved complete resolution of the pleural effusions. This case illustrates the variable clinical presentation of HHV-8-associated MCD in a patient living with HIV.

Background

Castleman disease comprises a group of rare polyclonal B-cell lymphoproliferative disorders characterised by abnormal overgrowth of lymphoid tissue and angiofollicular hyperplasia.¹ The disease can be broadly classified according to the extent of lymph node involvement and the underlying pathophysiologic mechanisms. Based on the extent of lymph node involvement, Castleman disease is divided into unicentric Castleman disease (UCD) and multicentric Castleman disease (MCD). The multicentric form is further subdivided into idiopathic MCD and human herpesvirus 8 (HHV-8)-associated MCD, with the latter occurring in both HIV-positive and HIV-negative individuals.²

The clinical manifestations of MCD typically include constitutional (B) symptoms, splenomegaly, pleural effusion and lymphocytic interstitial pneumonitis.³ Numerous case series and reports have described HHV-8-associated MCD in the USA, Australia and Europe,^4–8 whereas reports from Southeast Asia, including Thailand, remain scarce.^{9 10} However, its recognition remains particularly challenging in tuberculosis (TB)-endemic settings because its clinical manifestations may overlap with those of disseminated tuberculosis and lymphoma.

We describe HHV-8-associated MCD in a patient living with HIV, highlighting the diagnostic challenges of distinguishing this condition from TB and lymphoma in a TB-endemic setting.

Case presentation

A Thai man in his early 30s presented to our hospital for a second opinion after 4 months of progressive constitutional symptoms. He had previously been independent in activities of daily living and had no known medical conditions. His illness began with low-grade fever, persistent non-productive cough, bilateral cervical lymphadenopathy, and a transient erythematous rash over the forearms and legs.

He was diagnosed with HIV infection (CD4 count 227 cells/mm³ (470–1404 cells/mm³; 15% (24.1%–50.7%); HIV viral load was not measured at diagnosis) and late latent syphilis. He was started on tenofovir/lamivudine/dolutegravir and benzathine penicillin G. Initial investigations showed mild eosinophilia, while chest radiography was unremarkable.

Over the following 2 months, he developed progressive fatigue, anorexia and significant functional decline. Repeated microbiological investigations for TB, including sputum acid-fast bacilli (AFB) smears, TB nucleic acid amplification test (NAAT) and mycobacterial cultures, were negative. Despite antiretroviral therapy, his symptoms progressed with persistent low-grade fever, night sweats, dry cough, anorexia and bilateral cervical lymphadenopathy. Chest radiography subsequently demonstrated pulmonary infiltrates. Fine-needle aspiration (FNA) of a cervical lymph node revealed mixed small- and medium-sized lymphoid cells without evidence of malignancy, while bacterial, fungal and mycobacterial stains, cultures and TB NAAT remained negative. Despite negative sputum immunofluorescence and PCR testing for Pneumocystis jirovecii, he was empirically treated for presumed P. jirovecii pneumonia with primaquine and clindamycin; however, his symptoms failed to improve.

One month later, he developed progressive exertional dyspnoea, pleuritic right-sided chest pain, orthopnoea, persistent fever and drenching night sweats. Over the course of his 4-month illness, he had experienced marked weight loss, decreasing from 85 kg to 65 kg. He was therefore referred to our hospital for further evaluation. On presentation, his vital signs revealed mild tachycardia (pulse rate 108/min) and a body temperature of 36.6°C. Respiratory examination showed decreased chest expansion, reduced tactile fremitus and dullness to percussion at the right lower one-third of the lung field, consistent with right-sided pleural effusion observed on chest radiography. The liver was palpable 2 cm below the right costal margin with a span of 14 cm at the midclavicular line, and splenic dullness was present. Lymph node examination revealed a 1×1.5 cm rubbery, mobile, non-tender lymph node in the right lower anterior cervical region, along with multiple subcentimetre lymph nodes in the bilateral anterior cervical areas. The patient’s clinical and laboratory findings are summarised in table 1.

Table 1. Timeline of clinical course before referral.

Time before referral	Clinical features	Key investigations	Treatment
4 months	Low-grade fever, dry cough, bilateral cervical lymphadenopathy and transient erythematous rash.	New HIV diagnosis (CD4 227 cells/mm3, 15%); RPR 1:512; normal chest radiograph	Tenofovir/lamivudine/dolutegravir; benzathine penicillin G×3 doses
3 months	Persistent constitutional symptoms	Sputum AFB smear, TB NAAT, fungal and mycobacterial cultures negative	Supportive care
2 months	Progressive fatigue, anorexia and activity limitation	Anaemia requiring transfusion; fasting plasma glucose 243 mg/dL; HbA1c 7.0%. Cervical-node FNA: reactive lymphoid cells; no malignant cells; bacterial, fungal and mycobacterial studies and TB NAAT negative Pulmonary infiltration on chest radiograph	Packed red-cell transfusion; oral hypoglycaemic agents Primaquine plus clindamycin for 3 weeks
1 month	Persistent fever, dry cough, night sweats and cervical lymphadenopathy	–	Amoxicillin/clavulanate plus trimethoprim/sulfamethoxazole
2 weeks	Persistent symptoms despite treatment; pleuritic chest pain	New right pleural effusion on chest radiograph	–

AFB, acid-fast bacilli; ART, antiretroviral therapy; FNA, fine-needle aspiration; NAAT, nucleic acid amplification test; RPR, rapid plasma reagin; TB, tuberculosis.

Investigations

Initial laboratory investigations showed a haemoglobin level of 94 g/L (130–170 g/L), white blood cell count of 10.8×10⁹/ L (4.5–11.0 ×10⁹/ L), neutrophils 27% (40.0%–70.9%), lymphocytes 31% (22.2%–43.6%), eosinophil 38% (0%–4.1%) and a platelet count of 285×10⁹/L (150–450×10⁹/L). Blood chemistry results were as follows: urea nitrogen of 9 mg/dL (7–20 mg/dL), creatinine of 0.91 mg/dL (0.70–1.20 mg/dL), albumin of 3.4 g/dL (3.5–5.0 g/dL), globulin of 5.9 g/dL (2.0–3.3 g/dL), total bilirubin of 0.28 mg/dL (0.20–1.20 mg/dL), direct bilirubin of 0.16 mg/dL (0.0–0.5 mg/dL), aspartate aminotransferase of 26 U/L (5–35 U/L), alanine aminotransferase of 7 U/L (0–40 U/L) and alkaline phosphatase of 103 U/L (40–120 U/L), lactate dehydrogenase 165 U/L (125–220 U/L), CD4 count 562 cells/mm³ (470–1404 cells/mm³; 19% (24.1%–50.7%)) and HIV viral load 46 copies/mL. Chest radiography demonstrated bilateral pleural effusions, more prominent on the right side. CT of the chest revealed generalised lymphadenopathy involving the lower neck (sublingual, lower cervical and supraclavicular), peribronchial, prevascular, mediastinal and axillary regions, along with interlobular septal thickening and peribronchovascular thickening (figure 1).

Figure 1. CT of the chest revealed bilateral pleural effusion with generalised lymphadenopathy involving the lower neck (sublingual, lower cervical and supraclavicular), peribronchial, prevascular, mediastinal and axillary regions, along with interlobular septal thickening and peribronchovascular thickening.

Pleural fluid analysis revealed serosanguineous fluid with a lymphocyte-predominant exudate. Gram, AFB, modified AFB, Wright and Gomori methenamine silver stains showed no organisms; bacterial, fungal and mycobacterial cultures were negative. NAAT and PCR for Mycobacterium tuberculosis complex were negative. Pleural biopsy and bronchial biopsy were also performed, and all results were negative. Pleural and bronchial biopsies did not yield a specific diagnosis. For eosinophilia, alternative causes were considered. Stool microscopy showed no parasites, and agar plate culture for Strongyloides stercoralis and hookworm was negative.

A lymph node biopsy was performed, which demonstrated radially oriented hyalinised or sclerotic blood vessels penetrating into germinal centres, forming characteristic hyaline-vascular (‘lollipop’) lesions (figures 2 and 3). The mantle zones were expanded, with lymphocytes arranged in concentric (‘onion-skin’) rings surrounding the germinal centres.

Figure 2. Radially oriented hyalinised or sclerotic blood vessels penetrate into germinal centres, forming hyaline-vascular (lollipop) lesions (blue arrows).

Figure 3. Mantle zones are expanded with lymphocytes arranged in concentric (onion-skin) rings around germinal centres (black arrow).

Immunohistochemical analysis demonstrated positive staining for HHV-8 latency-associated nuclear antigen 1 (LANA-1) in scattered cells located outside the germinal centres, displaying plasmacytoid morphology (figure 4). The diagnostic immunophenotype showed CD20-positive B-cell areas and scatter outside germinal centre, CD3-positive paracortical T cells and scatter in germinal centre, CD138-positive plasma cells, polytypic plasma cells with a kappa:lambda ratio of approximately 2:1, and no abnormal cyclin D1-positive population. Epstein-Barr virus-encoded RNA (EBER) in situ hybridisation showed scattered Epstein-Barr virus (EBV)-positive cells, varying in size. There was no histologic or immunohistochemical evidence of carcinoma or overt lymphoma. The lymph node architecture showed features consistent with the hyaline-vascular type of Castleman disease, with focally scattered HHV-8-positive plasmacytic cells within the mantle zone. These findings were diagnostic of Kaposi sarcoma-associated herpesvirus (KSHV/HHV-8)-associated MCD, a subtype predominantly observed in HIV-positive individuals.

Figure 4. HHV-8 latency-associated nuclear antigen immunohistochemistry found scattered positive HHV-8 cells outside germinal centre (circle) with plasma cell appearance.

Treatment

The patient continued antiretroviral therapy with tenofovir/lamivudine/dolutegravir and was initiated on rituximab 375 mg/m² intravenously once a week for four cycles.

Outcome and follow-up

A partial clinical response was achieved after completion of rituximab treatment. There was minimal pleural effusion at the right pleura, but the lymph node could not be palpated. At the 4-month follow-up, the patient reported resolution of dyspnoea and cough, and chest imaging confirmed complete resolution of bilateral pleural effusions. At the 12-month follow-up, the patient remained clinically well, with no recurrence of any features suggestive of MCD relapse. Follow-up chest radiography showed complete resolution of the previous pleural effusions, with no new pulmonary abnormality.

Discussion

MCD is a rare, non-clonal lymphoproliferative disorder characterised by systemic inflammation, lymphoid hyperplasia and cytokine dysregulation, most notably viral interleukin-6 (IL-6) and vascular endothelial growth factor overproduction.¹¹ In HIV-positive individuals, the majority of MCD cases are associated with HHV-8, also known as KSHV.¹² HHV-8-infected plasmablasts are the main source of viral IL-6, which mimics human IL-6 activity and drives fever, cytopenia, hepatosplenomegaly and generalised lymphadenopathy.²

In the present case, the patient exhibited classical systemic manifestations of HHV-8-associated MCD, including prolonged fever, generalised lymphadenopathy, hepatosplenomegaly and pleural effusion. Histopathological findings revealed hyaline-vascular features with scattered HHV-8-positive plasmacytoid cells, confirming the diagnosis.¹ Although the hyaline-vascular subtype is more frequently observed in UCD, hybrid morphology may occur in multicentric forms, particularly in patients with HIV infection.³

HHV-8, a member of the Herpesviridae family and classified as a gamma-2 herpesvirus, is responsible for a broad spectrum of clinical manifestations in humans. The differential diagnosis of HHV-8-associated diseases includes Kaposi sarcoma, primary effusion lymphoma, KSHV-associated inflammatory cytokine syndrome and HHV-8-positive diffuse large B-cell lymphoma (DLBCL).¹³ In the present case, the absence of monoclonal proliferation and negative immunohistochemical staining for malignancy effectively excluded HHV-8-positive DLBCL. These findings, together with the presence of HHV-8-positive plasmacytoid cells in the lymph node and characteristic hyaline-vascular histopathology, supported the diagnosis of HHV-8-associated MCD.

Marked eosinophilia was observed at presentation (absolute eosinophil count, 4104 cells/µL). Although eosinophilia is not a typical diagnostic feature of HHV-8-associated MCD, it has been reported in MCD and may reflect cytokine dysregulation, including IL-5-mediated eosinophil proliferation in selected cases.¹³ In this patient, the temporal association between progressive systemic inflammation and hypereosinophilia suggested that eosinophilia may have represented a reactive manifestation of the underlying disease. However, cytokine measurements, including IL-5 and IL-6, were not available; therefore, a direct mechanistic association could not be confirmed.

HHV-8-associated MCD has occasionally been reported as a manifestation of immune reconstitution inflammatory syndrome (IRIS) following initiation of antiretroviral therapy (ART).¹⁴ However, IRIS was considered unlikely in our patient because the clinical manifestations were present before ART was initiated. Moreover, there was no clinical deterioration temporally associated with immune recovery after ART that would fulfil the typical features of unmasking or paradoxical IRIS.

Given that HHV-8-associated MCD may clinically mimic other conditions, particularly disseminated TB and lymphoma, establishing an accurate diagnosis is especially important in TB-endemic regions. In Thailand, such a presentation may be readily attributed to TB. However, although current diagnostic tests for TB have good diagnostic performance, active disease may not always yield microbiological confirmation because of paucibacillary disease, sampling limitations and the imperfect sensitivity of available tests. This case therefore underscores the importance of histopathologic confirmation, including HHV-8 immunostaining, together with careful exclusion of alternative diagnoses. Empirical anti-TB treatment should be used with caution and should not delay definitive tissue diagnosis when the clinical picture is atypical or microbiological investigations remain inconclusive. The clinical and laboratory features distinguishing HHV-8-associated MCD from lymphoma and disseminated TB are summarised in table 2.

Table 2. Comparison of the clinical and laboratory features of HHV-8-associated MCD, lymphoma and disseminated tuberculosis.

Disorder	Typical clinical features	Key pathology/cytology	HHV-8-related findings
HHV-8-associated MCD	Fever, generalised lymphadenopathy, hepatosplenomegaly, cytopenias, hypoalbuminaemia, hypergammaglobulinaemia, oedema/effusions	Preserved architecture; regressed germinal centres; onion-skin mantle zones; lollipop vessels; plasmacytosis	LANA-positive plasmablasts in mantle zones
Kaposi sarcoma	Violaceous skin/mucosal lesions; may involve viscera	Spindle-cell vascular proliferation with slit-like spaces	LANA-positive spindle cells
Primary effusion lymphoma	Serous-cavity effusion, without solid mass	Large plasmablast/immunoblast-like malignant cells in effusion; often CD20-negative	Tumour cells LANA-positive; often EBER-positive
HHV-8-positive DLBCL	Systemic symptoms with nodal/extranodal masses; often with MCD	Effacing sheets of large monotypic plasmablastic cells	LANA-positive tumour cells; typically EBER-negative
Disseminated tuberculosis	Fever, generalised lymphadenopathy, lung infiltration, sometimes hepatosplenomegaly	Necrotising granulomatous inflammation	–

Adapted by authors from Dalla et al and Khan

DLBCL, diffuse large B-cell lymphoma; EBV, Epstein-Barr virus; HHV-8, human herpesvirus 8; LANA, latency-associated nuclear antigen; MCD, multicentric Castleman disease.

The initial use of FNA followed by a subsequent excisional biopsy likely contributed to the diagnostic delay. A more expedited transition from FNA to excisional lymph node biopsy might have shortened the diagnostic process in this case. FNA has limited diagnostic use for MCD because the diagnosis relies on evaluation of the overall lymph node architecture and characteristic histopathological features, which are best assessed using an excisional biopsy.

Nevertheless, this delay should not be viewed solely as a consequence of individual clinical decision-making. Rather, it reflects the practical challenges of diagnosing a rare HIV-associated lymphoproliferative disorder in a TB-endemic, resource-limited low-income and middle-income country. In such settings, common infectious diseases such as disseminated TB are appropriately prioritised in the differential diagnosis, while access to advanced diagnostic modalities and timely excisional biopsy may be limited.

HHV-8 DNA testing in plasma, whole blood and tissue was not performed in this case because these assays were not available at our institution. Instead, the diagnosis was established clinicopathologically on the basis of systemic multicentric disease, characteristic lymph-node architecture and HHV-8 LANA-1 positivity in mantle-zone plasmacytic cells. The absence of HHV-8 DNA testing is a limitation of this report, as quantitative viral load measurements may provide additional virologic correlation and support disease activity assessment.

Management of HHV-8-associated MCD focuses on controlling viral replication, suppressing B-cell proliferation and modulating IL-6-mediated inflammation.¹¹ Rituximab, a monoclonal antibody directed against CD20, is considered first-line therapy and has shown excellent outcomes in both HIV-positive and HIV-negative patients. Outcomes for patients with HHV-8-associated MCD have improved markedly, with overall survival increasing from 42% to 94% at 2 years and from 33% to 90% at 5 years following the introduction of rituximab-based therapy.¹⁵ In this case, the observed response likely reflected the combined effect of rituximab-based MCD therapy and optimised ART, rather than rituximab alone. The patient has remained in sustained remission to date. These findings are consistent with previous reports demonstrating durable disease control, and rituximab was generally well tolerated, with only mild to moderate adverse effects. The most frequently reported infectious complications were herpesvirus reactivations.¹⁶ A 5-year relapse-free survival rate of 82% has been reported following rituximab-based therapy; however, the relapse rate after a second remission is considerably higher, reaching 53% at 5 years.¹⁷ Despite improved survival outcomes, close long-term follow-up remains essential, as disease recurrence, Kaposi sarcoma or secondary lymphoma may develop during continued observation.

In severe disease, concomitant Kaposi sarcoma or rituximab failure, treatment strategies may include rituximab combined with liposomal doxorubicin or etoposide, and repeat rituximab-based treatment for relapse; treatment selection should be individualised according to disease severity, coexisting HHV-8-associated malignancy, and available expertise.¹¹

In highlighting the real-world diagnostic challenges encountered in a TB-endemic, resource-limited setting. This case demonstrates how HHV-8-associated MCD can closely mimic disseminated TB and lymphoma, leading to delayed diagnosis when more common infectious aetiologies are appropriately prioritised. Based on these findings, we propose a practical diagnostic algorithm for evaluation as in figure 5. We hope this report offers clinically relevant lessons that are applicable to physicians practising in similar endemic settings.

Figure 5. Proposed clinical algorithm illustrating the differential diagnosis for distinguishing MCD from disseminated TB and lymphoma in endemic regions. Adapted by the authors from Wu et al,² Khan,¹⁹ WHO²⁰ and National Institute for Health and Care Excellence.²¹ ADA, adenosine deaminase; AFB, acid-fast bacilli; CBC, complete blood count; CRP, C-reactive protein; CSF, cerebrospinal fluid; ESR, erythrocyte sedimentation rate; LANA-1, latency-associated nuclear antigen 1; LDH, lactate dehydrogenase; LFT, liver function test; NAAT, nucleic acid amplification test; TB, tuberculosis.

Learning points.

• In tuberculosis (TB)-endemic settings, definitive diagnosis should be established before empirical anti-TB treatment, as human herpesvirus 8 (HHV-8)-associated MCD may mimic disseminated TB or lymphoma.

• This case highlights the importance of maintaining a high index of suspicion for HHV-8-associated MCD in HIV-positive patients presenting with systemic inflammatory symptoms, lymphadenopathy and effusions.

• Early recognition, histopathologic confirmation with HHV-8 immunostaining and prompt initiation of rituximab-based therapy are essential for favourable outcomes.

• The combination of antiretroviral therapy and B-cell-directed immunotherapy can achieve disease remission and prevent disease-related morbidity.