OVERVIEW: What every clinician needs to know

Pathogen name and classification

Chromoblastomycosis is a disease caused by one of a group of dark-walled fungi (phaeohyphomycetes). The most common etiologic agent is Fonsecaea pedrosoi. Other fungi that cause this disease include Cladophialophora carrionii, Phialophora verrucosa, and Rhinocladiella aquaspersa.

What is the best treatment?

  • There is no proven treatment of choice for this disease. Most commonly, antifungal treatment with or without adjunctive surgical or local heat therapy is employed.

    Itraconazole, terbinafine, or a combination of these antifungal agents appears to be the best current therapy of this disease. Itraconazole may be used at doses of 200-400 mg daily or 400 mg daily for 1 week each month (pulse dosing). Terbinafine is typically used at a dose of 500 mg daily, although 500 mg twice daily has also been used. Posaconazole has also been used successfully in a few patients. Treatment is typically provided for 6-12 months.

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    Surgical removal of smaller lesions has been successful. Prolonged (2-12 month) local heat therapy (42-46°C) has been used. Adjunctive cryotherapy is commonly used in combination with antifungal therapy.

How do patients contract this infection, and how do I prevent spread to other patients?

  • Epidemiology

    The causative agents are found in the soil and cause disease after they are inoculated into the skin and subcutaneous tissues.

    It is most commonly seen in tropical and subtropical climates, although they can be found worldwide. Its highest incidence is in areas with high annual rainfall.

    It is endemic in Madagascar, Brazil, Mexico, Venezuela, and Costa Rica. Highest prevalence appears to be in Madagascar.

    It is most commonly seen in men, 40-69 years of age, who work outdoors (e.g., farmers and woodcutters) and who don’t wear footwear.

  • Infection control issues

    Chromoblastomycosis is not transmitted between humans or from animals to humans.

    No vaccination is available.

What host factors protect against this infection?

  • The immune response to this disease is not well understood. Disease appears to be secondary to an ineffective cell-mediated immune response.

  • Risk for chromoblastomycosis appears to be associated with that of minor skin trauma and inoculation of the causative fungus from the environment. No associations between this disease and specific immunocompromised diseases or treatments have been made.

  • Host response on histopathology is that of chronic suppuration and granulomatous response. Milder disease has been associated with higher gamma-interferon and lower interleukin-10 levels, when compared to levels seen in patients with severe disease.

What are the clinical manifestations of infection with these organisms?

  • Chromoblastomycosis is a chronic infection localized to the skin and subcutaneous tissues that involves primarily the lower extremities. Infection begins with papules that enlarge to form plaques that become scaly. The lesions slowly and progressively enlarge over months to years and become warty or cauliflower-like in appearance.

What common complications are associated with this disease?

  • Disfigurement and secondary bacterial infections are the most common complications.

  • Development of squamous cell carcinoma has been described in long-standing lesions.

How should I identify these organisms?

Chromoblastomycosis produces pathognomonic structures called sclerotic bodies or muriform cells (also called Medlar or copper penny bodies). These are 4-12 µm, darkly-pigmented, thick-walled fungal cells that have transverse crosswalls.

  • Diagnosis is made by identifying the muriform cells recovered from typical lesions. These can be seen on superficial scrapings treated with potassium hydroxide (KOH) or on biopsy samples of lesions. The muriform cells are visible on standard hematoxylin and eosin stains of biopsy material.

  • Culture diagnosis can be performed from scrapings or biopsy material. Standard mycologic media can be used to recover the dark molds that cause the disease.

  • Enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) diagnostics have been developed but are not widely available outside of the endemic areas.

How do these organisms cause disease?

  • Specific virulence factors have not been described for the organisms isolated from cases of chromoblastomycosis. However, these fungi produce melanin, which is a virulence factor for many molds.

WHAT’S THE EVIDENCE for specific management and treatment recommendations?

Baddley, JW, Dismukes, WE, Kauffman, CA, Pappas, PG, Sobel, JD, Dismukes, WE. “Chromoblastomycosis”. Essentials of clinical mycology. 2011. pp. 427-33.

Bonifaz, A, Saul, A, Paredes-Solis, V. “Treatment of chromoblastomycosis with terbinafine: experience with 4 cases”. J. Dermatol Treat. vol. 16. 2005. pp. 47-51.

Esterre, P, Queiroz-Telles, F. “Management of chromoblastomycosis: novel perspective”. Curr Opin Infect Dis. vol. 19. 2006. pp. 148-52.

Negroni, R, Tobin, A, Bustamante, B. “Posaconazole treatment of refractory eumycetoma and chromoblastomycosis”. Rev Inst Med Trop Sao Paulo. vol. 47. 2005. pp. 339-46.