MRI findings in patient with primary cutaneous nocardiosis: A case report

Abstract

Nocardia is a genus of gram-positive, filamentous, aerobic bacteria that belongs to the Actinomycetales order. With over 50 species, it is ubiquitous in dust, soil, decaying organic matter, and stagnant water. Inhalation of the pathogen often leads to pulmonary nocardiosis, while extrapulmonary nocardiosis can affect the central nervous system, skin, and subcutaneous tissues. Primary cutaneous nocardiosis occurs when the pathogen is introduced through a skin lesion or insect bite, for example, this report presents a case of primary cutaneous nocardiosis in a patient with Minimal Change Glomerulonephritis and iatrogenic immunosuppression. Magnetic resonance imaging revealed extensive involvement of the skin, subcutaneous tissue, and lower limb muscles.

Introduction

Genus Nocardia belongs to the Actinomycetales order and includes more than 50 species of gram-positive, filamentous, aerobic, ubiquitous bacteria commonly found in dust, soil, decaying organic matter and stagnant water [1,2]. As an opportunistic pathogen, it is widely responsible for acute or chronic infections in humans of any age group. The rate of infection is especially high in elderly males who have weakened cell-mediated immunity. Recurrent infections are common in patients who have undergone organ transplantation, or are currently undergoing steroid therapy, have lymphoma, or have acquired immuno-deficiency syndrome [1,3]. The most frequently observed manifestation of the condition is pulmonary nocardiosis, which is caused by inhalation of the pathogen. Conversely, extrapulmonary nocardiosis can affect the central nervous system, skin, and subcutaneous tissues [1,4]. Primary cutaneous nocardiosis (PCN) occurs following transcutaneous inoculation of the pathogenic microorganism due to a skin continuum solution (lesion, insect bite). It is a rare condition generally involving superficial skin tissue such as pustules, pyoderma, abscess, ulcers, granulomas, cellulitis, lymphocutaneous syndrome, or mycetoma. Nocardial mycetoma, also known as actinomycetoma, is a chronic disease that is commonly found in tropical regions and mainly affects the lower limbs but can also impact the hands and forearms [1,2,[4], [5], [6], [7]. In this report, we present a case of PCN in a patient with a clinical history of Minimal Change Glomerulonephritis and iatrogenic immunosuppression. Magnetic resonance imaging (MRI) shows extensive involvement of skin and subcutaneous tissue and lower limb muscles.

Case presentation

This paper is a case report that was not performed any experimentation, so no Ethics committee approval or Helsinki Declaration statement is mandatory. We present a case of a 70-year-old male patient who reported swelling in both of his lower limbs and the onset of new arterial hypertension. As a result, he was admitted to a specialized nephrology department. Routine biochemical tests revealed elevated proteinuria, and hypoalbuminemia. The clinical and biochemical results were initially consistent with a systemic condition affecting the admitted patient. In order to exclude any secondary glomerulonephritis, we performed a kidney biopsy, whose results showed a histologic pattern compatible with a minimal change glomerulopathy. Later on, high-dose steroids were considered as a treatment option. For the first 3 days, 500 mg/day of Methylprednisolone Sodium Succinate was given through intravenous infusion. Then, the patient was given oral Prednisone at a dose of 50 mg/day for 17 weeks while gradually reducing the use of glucocorticoids. As the glucocorticoids tapering process continued, the patient's creatinine levels and proteinuria increased, indicating a resurgence of the disease's biochemical manifestations. Therefore, the process was stopped, and it became necessary to start again with an initial dose of Prednisone (50 mg/day). A few months later, the patient reported the sudden onset of marked swelling in his right lower limb, accompanied by worsening pain in the popliteal fossa, knee, and lower third of the thigh. After seeking advice from an orthopaedic specialist, the patient underwent a Doppler ultrasound evaluation of the lower limbs and an X-ray of the right knee and leg. The Doppler ultrasound ruled out any arteriovenous thrombosis but revealed the presence of an irregular, hypoechoic formation in the popliteal fossa. The X-ray did not show any signs of trauma or pathologic bone damage, instead, it showed widespread absorption of soft tissue, primarily in the posterior area. Following the development of intermittent fever in a patient with iatrogenic immunosuppression, he was admitted to our hospital with the suspicion of a subacute infectious inflammatory disease. Upon admission, a series of blood tests were performed, revealing a neutrophilic leucocytosis and elevated levels of C-Reactive Protein and ferritin. The patient then underwent a lower limb MRI examination (using GE Healthcare's SIGNA Voyager 1.5T) with comparative scans of the opposite limb. The examination utilized axial and coronal planes T1w and T2w sequences, with suppression of the adipose tissue signal, both before and after the administration of the paramagnetic intravenous contrast medium Gadobutrol (1 mmol/mL). The exam results showed swelling in the right lower limb subcutaneous tissue, along with multiple fluid accumulations. After the administration of the contrast medium, these collections exhibited an enhancing rim in T1-weighted sequences. The bones were not affected in the areas covered by the exam (as seen in Fig. 1, Fig. 2, Fig. 3). A culture taken from the exudative material confirmed Nocardia farcinica as the cause of the infection. The patient underwent surgical drainage and was given targeted antibiotic therapy based on the results of the antibiogram. Brain MRI and chest and abdomen computed tomography examinations were performed to evaluate significant focal pathologic changes. After these exams did not report any other site of active disease, PCN diagnosis was confirmed. After a 10-week antibiotic therapy (moxifloxacin 400 mg/ QD), the follow-up MRI showed a nearly complete resolution of the previously identified fluid collections (Figs. 4 and 5).

Fig. 1.

Thighs—coronal T1 FSE (A), STIR slices in anterior-posterior direction (B-D): multiple fluid/abscess collections in the muscles of the posterior and antero-lateral compartment of the thigh (yellow arrows).

Fig. 2.

Thighs—coronal and axial T2 (A, B); Coronal and Axial T1 FS (FAT SAT) after intravenous administration of paramagnetic contrast agent (Gadobutrol 1.0 mmol/mL) (C, D): the fluid collections with a confluent appearance and intense peripheral impregnation (yellow arrows), compatibly with an inflammatory/abscess nature.

Fig. 3.

Thighs—coronal T2 (A), coronal and axial T1 FS (FAT SAT) after intravenous administration of paramagnetic contrast agent (Gadobutrol 1.0 mmol/mL) (B, C): Fluid collections located in the postero-medial compartment of the right leg, extending from the popliteal cavity to the distal third of the tibial shaft, the largest in the context of the gastrocnemius bundles (yellow arrows). Similar fluid collections are also present on the left leg, in the lateral compartment (red arrows). Concomitant edematous imbibition of subcutaneous tissues. The bone profile of the tibial diaphyses is preserved, without evident interruptions and / or periosteal reactions. Fluid/abscess collections with intense marginal impregnation (green arrows).

Fig. 4.

Thighs—coronal T1w F.S.E. (A), T2 (B), STIR (C), LAVA-Flex after intravenous administration of paramagnetic contrast agent (D). MRI images performed after 10 weeks of targeted antibiotic therapy, documenting complete resolution of abscess collections in the thighs.

Fig. 5.

Thighs—coronal T2 (A, B), LAVA-flex after intravenous administration of paramagnetic contrast agent (C). Complete resolution of leg abscess collections.

Discussion

Nocardiosis is a sporadic infectious disease, ubiquitarian and present in any age group, with a significant relative prevalence in elder men, in cell-mediated immune deficiency [1,8]. PCN is a less frequent form of nocardiosis, which is generally caused by transcutaneous entry of the pathogen, compared to more common forms of nocardiosis that result from inhalation of contaminated dust and can lead to disseminated disease, including involvement of the central nervous system [1,3]. Cutaneous nocardiosis typically presents as a sudden and limited skin and subcutaneous infection, manifesting as pyoderma, cellulitis, or abscess formations. It can also spread to the surrounding lymph nodes and be referred to as a lymphocutaneous condition. If left untreated, the infection can become chronic and lead to the formation of mycetoma [4], [5], [6]. In cases of acute muscle and skin nocardiosis, diagnostic imaging usually shows nonspecific signs such as sores, cellulitis, abscesses, and fistulas. The dominant feature on MRI is the detection of multiple, complex lesions and fluid collections. These findings can be confused with other conditions such as cancer metastases, muscle infarction, parasitic infections, tuberculosis, or other bacterial infections. However, the presence of peripheral ring enhancement on T1-weighted images after contrast medium administration can help the radiologist determine that the lesion is an abscess. On the other hand, a history of a primary tumor or long-term microvascular damage is necessary to support a diagnosis of metastatic cancer or muscle infarction. Moreover, contaminated food intake history and positive parasites help to distinguish from parasitic infections [9,10]. Although MRI results lack specificity, imaging plays a crucial role in determining the extent of the infectious process and guiding surgical drainage of purulent collections. Regardless of the initial symptoms, all nocardiosis patients must be thoroughly evaluated to detect potential systemic spread. In this regard, computed tomography and MRI with or without contrast medium are essential in achieving this goal. Therefore should be performed even in the absence of suspicious systemic involvement. Since nocardiosis tends to chronicity and local relapse, it is advisable to evaluate the pathologic process's resolution before stopping specific antibiotic therapy [9], [10], [11], [12], [13], [14]. The interpretation of the diagnostic imaging was crucial in diagnosing and managing a patient with a rare condition like PCN. In this case we are reporting the patient has a history of taking high doses of corticosteroids. This, combined with the sudden onset of symptoms in a relatively young elderly person, makes it difficult to distinguish between a wide range of systemic and local conditions. However, the results of laboratory and imaging tests (such as the absence of thrombotic events in the iliac-femoral vessels as seen on Doppler ultrasound, increased levels of neutrophils, and elevated inflammation markers) suggest that the cause of the symptoms is likely to be an inflammatory process. The suspicion of an infectious cause was further strengthened by the patient's personal history and laboratory results that showed inflammation (neutrophilic leukocitosis, increased C-reactive protein, increased ferritin serum level). The MRI findings of multiple fluid collections and widespread oedematous imbibition in the muscles of the thigh and leg suggested an infectious or inflammatory process affecting the skin and soft tissues. Microbial culture of the purulent collection confirmed the presence of a N farcinica bacterium, as identified through polymerase chain reaction (PCR) testing. In the reported case, the multiple fluid collections in the lower limb muscles and subcutaneous tissues were easily detected, which helped in the diagnosis. Moreover, the MRI findings were valuable in managing the patient by guiding the drainage of the purulent collections and providing information on the appropriate antibiotic therapy. In the diagnosis and treatment of inflammatory-infectious diseases, radiologists play a crucial role. They must be knowledgeable about the clinical aspects and the radiological semiotics and must be able to accurately link the imaging results with the patient's medical history.

Patient consent

Informed written consent was obtained from the patient for publication of the case report and all imaging studies. Consent form on record.