Chromoblastomycosis

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Chromoblastomycosis is a long-term fungal infection of the skin[1] and subcutaneous tissue (a chronic subcutaneous mycosis).[2] The infection occurs most commonly in tropical or subtropical climates, often in rural areas. It can be caused by many different type of fungi which become implanted under the skin, often by thorns or splinters. Chromoblastomycosis spreads very slowly; it is rarely fatal and usually has a good prognosis, but it can be very difficult to cure. There are several treatment options, including medication and surgery.

The initial trauma causing the infection is often not noticed or forgotten. The infection builds at the site over a period of years, and a small red papule (skin elevation) appears. The lesion is usually not painful and there are few, if any symptoms. Patients rarely seek medical care at this point.

Several complications may occur. Usually, the infection slowly spreads to the surrounding tissue while still remaining localized to the area around the original wound. However, sometimes the fungi may spread through the blood vessels or lymph vessels, producing metastatic lesions at distant sites. Another possibility is secondary infection with bacteria. This may lead to lymph stasis (obstruction of the lymph vessels) and elephantiasis. The nodules may become ulcerated, or multiple nodules may grow and coalesce, affecting a large area of a limb.

The most informative test is to scrape the lesion and add potassium hydroxide (KOH), then examine under a microscope. (KOH scrapings are commonly used to examine fungal infections.) The pathognomonic finding is observing Medlar bodies, sclerotic cells. Scrapings from the lesion can also be cultured to identify the organism involved. Blood tests and imaging studies are not commonly used.

Chromoblastomycosis is believed to originate in minor trauma to the skin, usually from vegetative material such as thorns or splinters; this trauma implants fungi in the subcutaneous tissue. In many cases the patient will not notice or remember the initial trauma, as symptoms often do not appear for years. The fungi most commonly observed to cause chromoblastomycosis are Fonsecaea pedrosoi,[3] Phialophora verrucosa,[4] Cladosporium carrionii, and Fonsecaea compacta.[5]

Over months to years, an erythematous papule appears at the site of inoculation. Although the mycosis slowly spreads, it usually remains localized to the skin and subcutaneous tissue. Hematogenous and/or lymphatic spread may occur. Multiple nodules may appear on the same limb, sometimes coalescing into a large plaque. Secondary bacterial infection may occur, sometimes inducing lymphatic obstruction. The central portion of the lesion may heal, producing a scar, or it may ulcerate.

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