BI18: <i>Mycobacterium marinum</i> bacteraemia: a complication worth fishing for

Alternaria is a rare cause of fungal infection in the human host but has emerged as an increasing source of morbidity in the iatrogenically immunosuppressed, in particular solid organ transplant recipients (OTRs). This ubiquitous soil saprophyte is a common plant pathogen responsible for leaf blight and leaf spot on a wide variety of crops. It is a phaeohyphomycosis (melanin-producing fungus) and can manifest as a cutaneous infection, which poses both diagnostic and therapeutic challenges. We report a case of cutaneous alternariosis in a 69-year-old farmer 20 months after renal transplantation for diabetic nephropathy. Current immunosuppressive medications included mycophenolate mofetil and tacrolimus. He presented to dermatology with a 6-month history of two well-circumscribed, smooth, violaceous nodules (approximately 05 and 2 cm in diameter, respectively) on the right thigh. These were asymptomatic and had remained static in size since onset. There was no preceding history of trauma or inoculation at the site. The patient was systemically well. Examination revealed no associated lymphadenopathy. Routine blood tests, including inflammatory markers, were normal. Excision biopsy of one nodule revealed a dermal abscess with necrotizing granulomatous inflammation. Periodic acid-Schiff with diastase and Grocott stains showed numerous hyaline septated fungal hyphae with acute angle branching. Culture identified Alternaria spp. sensitive to itraconazole and posaconazole, intermediate to voriconazole. Definitive management with surgical excision of the second nodule and a 6-month course of oral posaconazole was initiated. Alternariosis occurs more frequently in immunocompromised individuals as Alternaria spp. are weakly pathogenic. Localized disease has been reported to manifest with rhinosinusitis, ocular infections, onychomycosis and cutaneous/subcutaneous infections. Cutaneous presentations are most frequent and can be variable, ranging from macules to violaceous nodules/plaques and ulcers. Disseminated disease is rare but if undiagnosed it can be fatal. We present a case of localized disease with no obvious entry site for inoculation, although the patient's occupation is likely to be relevant. Treatment remains a challenge in OTRs owing to drug-drug interactions through inhibition of cytochrome P450 enzymes. Posaconazole has an improved side-effect profile and more consistent bioavailability than itraconazole. Surgical excision is reported to be successful in reducing the burden of infection. Close surveillance is required to identify recurrence as early as possible. This case highlights the differential of rare fungal infections in OTRs presenting with nodules clinically suspicious of skin cancers and the management challenge it poses.