Subcutaneous mycoses: an aetiological study of 15 cases in a tertiary care hospital at Dibrugarh, Assam, northeast India.

Subcutaneous mycoses are a group of fungal infections of dermis and subcutaneous tissue which consist of sporotrichosis, chromoblastomycosis, phaeohyphomycosis, hyalohyphomycosis, mycetoma, subcutaneous zygomycosis, rhinosporidiosis, lobomycosis and disseminated penicilliosis. A total of 46 consecutive patients with clinically suspected subcutaneous mycoses attending various departments of Assam Medical College and Hospital were included in this prospective study to know the prevalence of subcutaneous mycoses in this eastern part of Assam. Direct microscopy in 10 and 40 % KOH, histopathological examination of biopsied tissue, colony characteristics on Sabourauds dextrose agar media both at 25 and 37 °C and detailed morphology of each fungus on lactophenol cotton blue mount were the basis of identification of the fungi. Subcutaneous mycoses were confirmed in 32.6 % (n = 15) cases. Out of 15 positive cases of subcutaneous mycoses, chromoblastomycosis was detected in six cases (n = 40 %), hyalohyphomycosis in three cases (n = 20 %), and lymphocutaneous sporotrichosis, disseminated penicilliosis and mycetoma in two cases each (n = 13.3 % each). In this study, seven different species of fungus were found to be responsible for five different clinical types of subcutaneous mycosis. Cladosporium cladosporioides, Bipolaris spicifera and Curvularia lunata were responsible for chromoblastomycosis, Fusarium oxysporum and Aspergillus terreus for hyalohyphomycosis, C. lunata for mycetoma, Sporothrix schenckii for lymphocutaneous sporotrichosis and Penicillium marneffei for disseminated penicilliosis. C. cladosporioides and C. lunata were the commonest black fungi causing subcutaneous mycosis in this sub-Himalayan belt. Rare species C. cladosporioides, B. spicifera and C. lunata were found to be causing chromoblastomycosis in this study.