Case Presentation: A 76-year-old female noted left fourth- and fifth-digit pain on day 12 receiving trimethoprim/sulfamethoxazole (TMP/SMX) and linezolid for purulent collections of Nocardia abscessus complex in the right gluteal and paraspinal muscles. She had a medical history of atrial fibrillation on apixaban, heart failure with preserved ejection fraction, and a history of deceased donor kidney transplant receiving daily tacrolimus and prednisone. She was afebrile, vitally stable, with labs that morning notable for a hemoglobin of 7.4 g/dL and a leukocyte count of 7.5 x109/L, representing a steady decline from a peak of 29.1 x109/L two weeks prior. Inspection of the left hand showed edema and the appearance of subcutaneous bullae over the dorsal ulnar aspects of the left hand. She had exquisite pain to light touch, most pronounced over the metacarpophalangeal joints. Range of motion was limited by pain. Ultrasound of the area revealed nonspecific soft tissue edema and hyperemia and no evidence of MCP joint synovitis. Dermatology was consulted for skin biopsy given the low likelihood of traditional bacterial cellulitis while on TMP/SMX and linezolid. Biopsy samples were sent for microbiology and dermatopathology. Fungal cultures resulted with growth of Alternaria species. Dermatopathology demonstrated deep dermal and pannicular neutrophilic and histiocytic inflammation with associated fungal microorganisms consistent with Alternaria infection. Infectious diseases consult recommended further imaging with MRI of L hand and wrist and initiation of posaconazole 300 mg daily for three months. MRI would reveal edema and small volume fluid about the fourth and fifth extensor tendons at the level of the metacarpal heads. There was also evidence of wrist joint synovitis. Hand surgery recommended conservative management with antifungals. The cutaneous infection resolved with complete remission and range of motion recovered without evidence of disability.
Discussion: The Infectious Disease Society of America (IDSA) guidelines for the management of skin and soft tissue infections give a strong, high evidence recommendation for early skin biopsy in immunocompromised patients for histologic and microbiologic evaluation for bacterial, fungal, viral, and parasitic causes[1]. In these patients, the IDSA also recommends consideration for dermatologic and surgical consults for early debridement, making these scenarios highly relevant for inpatient providers.Commonly found in soil, Alternaria infections are usually found in immunocompromised hosts, namely those with a history of solid organ transplant or recipients of chronic high dose corticosteroids. Even so, Alternaria is an unusual pathogen with only 210 human alternarioses reported between 1933 and 2008 of which 74.8% were cutaneous infections [2]. Deeper infections such as tenosynovitis were rarer still. Alternaria skin infections often present with erythema and verrucous like lesions, but presentations can be variable, including non-healing ulcers, nodules, and skin desquamation. Some cases of Alternaria infection can resolve with simple de-escalation of immunosuppression, but most cases will require antifungal therapy [2]. Itraconazole and posaconazole are first line agents for cutaneous Alternaria infections.
Conclusions: This case showcases a rare Alternaria cutaneous infection and serves as an important reminder to consider atypical causes of skin and soft tissue infection in immunocompromised patients.