Differential Diagnosis, Investigations, and Treatment:
The differential diagnoses included tuberculous and non-tuberculous mycobacterial skin infection, neutrophilic dermatosis, sarcoidosis, deep fungal infection of the skin, sporotrichiosis, and leishmaniasis. Multiple biopsies were taken for histopathologic examination, mycobacterial PCR analysis, acid-fast culture, bacterial, and fungal cultures.
Histopathology showed hyperkeratotic skin with parakeratosis, pseudo-epithiliomatous epidermis and marked mixed interstitial inflammation with granulomatous and abscess formation in the dermis in favor of an infectious process. Special stains, mycobacterial PCR and acid fast cultures were negative. Bacterial culture was positive for Streptococcus agalactiae and the patient was started on amoxicillin/clavulanic acid. However, lesions kept growing and became more exophytic and verrucous in appearance with overlying black dots (Fig. 1- c,d). A deep fungal infection of the skin was highly suspected, specifically chromoblastomycosis. Potassium Hydroxide examination of the black dots from the surface of the lesion showed numerous spherical spores, characteristic of muriform bodies (Fig. 2) and fungal culture on sabouraud dextrose agar grew brownish colonies confirming chromoblastomycosis. The patient was started on oral terbinafine 500 mg daily and once weekly sessions of cryotherapy without improvement after 6 weeks, then switched to oral itraconazole at 200 mg daily with no improvemen after 4 weeks.