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.