The disease

Chromoblastomycosis is a chronic infection of cutaneous and subcutaneous tissues. Lesions are clinically polymorphic, the most frequent are nodular, verrucous and tumoral. Many different species of fungi are associated with this infection but the three most common species are: Fonsecaea pedrosoi, Cladophialophora carrionii and Phialophora verrucosa.

The disease was first described in Brazil by Dr Max Rudolph, a German physician in 1914.

Epidemiology

The causative fungi have worldwide distribution, but chromoblastomycosis is most common in tropical areas. The black moulds are distributed in the soil, and associated with plants, especially palm trees and cacti. Patients become infected when injuries break the skin and allow the fungus to enter the body.

The highest prevalence of the disease is found in the Amazon region of Brazil, the northern part of Venezuela, and in Madagascar. The infection occurs most frequently in males and is not transmitted from human to human.

Clinical picture

After infection, a small elevated lesion develops. This is followed by a slow proliferation of tissue that produces crusted, verrucous or ulcerated lesions. If the infection is not treated, the lesions continue to grow and eventually resemble a tumour or a cauliflower.

Diagnosis

The fungi can be identified in skin scrapings or by biopsy. The fungi can also be detected by microscopic examination or cultured in the laboratory. If infection is present, microscopic examination reveals characteristic muriform cells. These large cells are round, chestnut shape, brown and with specific patterns. When the fungus is cultured, it can be identified using several different methods, but the best is DNA sequencing. Antibody testing is not useful in diagnosing this infection.

Surveillance and control

Accurate data on the incidence and prevalence are not available. For the purposes of surveillance, the disease is defined as: “a chronic (>3 months) cutaneous and subcutaneous fungal infection manifesting with verrucous, nodular and plaque lesions, depicting muriform fungal cells on microscopy.”

Chromoblastomycosis is considered an occupational disease, occurring among farm labourers, babassu coconut harvesters, lumberjacks, or vendors of farm products. Lack of protective shoes, gloves or garments and poor nutrition and hygienic habits are risk factors associated with chromoblastomycosis. Prevention is difficult, but it is useful to advise people not to walk barefoot in areas where infection has been detected.

Treatment

Treatment should begin as soon as possible. Results are poor in patients who have had lesions for a long time. In the first phase, surgery may be the best approach. Treatment with antifungal medicines is indicated for large lesions that cannot be treated surgically. Itraconazole, voriconazole and posaconazole have been used successfully. For cases that do not respond to antifungal monotherapy, the combination of itraconazole plus terbinafine may be considered.

Links and resources

• Chromoblastomycosis . Adelaide, South Australia, University of Adelaide, Mycology Online, 2012. This web page from the University of Adelaide provides useful information about and pictures of patients with chromoblastomycosis.
  
• Doctor Fungus. A Web page showing some useful information of Chromoblastomycosis.