Fungal arthritis also known as mycotic arthritis is the inflammation of the joint caused by fungus. The most common fungal infection of joints is caused by the Candida species, mainly, Candida albicans. Phaeohyphomycosis (PHM) is the group of mycoses caused by pigmented fungi. They are rare in occurrence and are mostly encountered in immunocompromised patients ^[1]. We present a case of fungal infection of the right ankle joint caused by PHM in a 56-year-old man.

A 56-years-old man presented to our outpatient department with pain and swelling over his right ankle joint for 2 years. There was no history of trauma. The local examination revealed diffuse swelling around the ankle with tenderness over the lateral and medial aspects. The range of movements was painful and restricted. Radiographs revealed diffuse soft-tissue shadow around the ankle with posterior osteophytes in the ankle joint (Fig. 1 and 2). MRI showed marrow edema with enhancement in the distal tibia and talus and calcaneum with multiple subchondral cysts with diffuse cortical erosions adjacent to the articular surfaces (Fig. 3). Ankle arthroscopy was performed and the synovial biopsy was done. Histopathological examination of the synovium showed hyperplastic synovium with well-formed granuloma comprising of epithelioid histocytes, Langhan`s type giant cells, and fibroblasts. Pigmented fungi were noted with phagocytosed fungal hyphae within multinucleated giant cells. All features were indicative of PHM (Fig. 4). The patient was immediately started with itraconazole 200 mg twice a day and physiotherapy. Anti-fungal therapy was given for 2 months, and the patient was relieved of pain and swelling by then. At 1-year follow-up, the patient is comfortable and carrying out his routine activities without any signs of any recurrences.

Fungal infection of the musculoskeletal system is rare but notorious for causing persistent, chronic, low-grade infection ^[2]. PHM is tissue infection caused by dematiaceous (pigmented) hyphae or yeasts. There are more than 150 species classified which are primarily soil and wood saprophytes causing opportunistic infections in humans. Skin and central nervous system are the most involved systems ^[3]. The following are the important risk factors for the fungal infection: immunosuppression by disease of medication (e.g., anti-tumor necrosis factor drugs), substance abuse, long-term presence of indwelling catheter, parenteral nutrition, diabetes mellitus, use of broad-spectrum antibiotics, HIV infection, organ transplantation ^[4]. Skin lesions following trauma mainly involve hands and feet. Subcutaneous granulomas are common in European countries. Lung and eye involvement is also common. Cerebral infections have maximum mortality rates. Skeletal system is rarely involved, and joint infections are either secondary to the direct spread following trauma or systemic spread through inhalation. The most important risk factors for PHM are history of trauma, diabetes mellitus, corticosteroid use, malnutrition, tumors, kidney transplantation, and chemotherapy. Systemic PHM is restricted to immunocompromised patients and is usually fatal ^[5,6]. Histopathology is diagnostic, due to large number of species cultures required to know the specific species of the organism and the antibiotic sensitivity. Histopathological features include granulomatous inflammation with necrosis and purulent debris with or without foreign material. Organisms appear as pigmented yeast in chains to hyphal forms in and around the granulomatous reaction. Molecular identification of fungi by polymerase chain reaction is rapid and specific in diagnosing PHM ^[7,8]. Itraconazole is drug of choice for the treatment of PHM. Alternatively, posaconazole can also be used. Solitary lesions can be managed with surgical excision and the disseminated lesions require systemic anti-fungal therapy. Only one such case of skeletal PHM has been reported in the literature before our report ^[9,10]. Our patient had no history of trauma or any wound around the joint, and infection by systemic spread is the most likely mode of infection. The diagnosis was confirmed by histopathological examination of the synovial tissue sent by arthroscopic biopsy and the patient was managed with oral itraconazole leading to full recovery.

Fungal arthritis is a rare condition and PHM is rarer. Diagnosis must be kept in mind while dealing with chronic foot and ankle swellings. Tissue biopsy and histopathological examination are gold standard for diagnosis. Early treatment with appropriate anti-fungal agent will give good functional results.

Histopathological examination after synovial biopsy is gold standard for the diagnosis of the fungal arthritis and early treatment with appropriate anti-fungal agents is pivotal for the good functional recovery of the patients.