User:Mr. Ibrahem/Tinea nigra

Tinea nigra is a fungal infection of the top layer of skin. It typically presents as a single 1 to 5 cm dark brown or black, non-scaly, flat, painless patch on the palms of the hand or soles of the foot. There is little or no skin inflammation. Typically it occurs in people who are otherwise healthy.

It is a type of phaeohyphomycosis rather than a tinea. Most cases are caused by Hortaea wernecki, a pigmented fungus, which is a dark yeast found in sewage, soil, rotting plant matter, and places with a high salt content such as moldy salted fish or on beaches, where contact with sand may result in transmission. Infection is by direct contact. The fungus enters and remains in the outer dead layer of skin, with no invasion of deeper tissues.

Diagnosis is looking at the rash, dermoscopy, microscopy or culture of skin scrapings. Other conditions that may present similarly includes Addison's disease, syphilis, pinta, yaws, melanoma, lentigines, palmer lichen planus. and junctional melanocytes nevus. Treatment is with topical Whitfield's ointment or salicylic acid ointment. Topical antifungals or itraconazole by mouth are other options. Scraping the lesion can be curative. Prevention is by general hygiene measures.

Tinea nigra is uncommon. It generally occurs in tropical and subtropical countries of Central or South America, the Caribbean, Europe, South East Asia, Australia, and the Far East. It is rare in Japan though not uncommon in the US. The disease was first described by Alexandre Cerqueira from Brazil in 1891. No cases in animals have been reported.