Chromoblastomycosis

Chromoblastomycosis, also called chromomycosis, is a chronic subcutaneous fungal infection caused by dematiaceous fungi, a group of saprophytic molds which produce dark (black) pigments. The pigmented fungi belonging to the Dematiaceae family are considered an emerging group of pathogenic fungi, at least in westernized countries. Dematiaceous fungi form pigmented hyphae, or fine branching tubes, and yeastlike cells in the infected tissues.

There are 3 kinds of diseases caused by black fungi: chromoblastomycosis, phaeohyphomycosis, and mycetoma. Five fungi known to cause chromoblastomycosis have been identified: Fonsecaea pedrosoi is the most prevalent. The genus Foncecaea contains two species, Fonsecaea pedrosoi and Fonsecaea monophora. Both species are soil and plant fungi and F. pedrosoi is also associated with forest litter decomposition. Other species include Phialophora verrucosa, Cladosporium carrionii, Fonsecaea compacta, and Rhinocladiella aquaspersa also occur in descending order of frequency. Less frequently, chromoblastomycosis is caused by Cladophialophora arxii, Exophiala spinifera, Exophiala dermatitidis, Exophiala jeanselmei and Wangiella dermatitidis.7



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Infection

The fungi enter the host through skin puncture wounds, usually on a thorn, splinter, or via insect bite or sting. Several months after the injury, painless papules or nodules appear on the affected area that slowly enlarge over time and can ulcerate. In the absence of prompt medical intervention, a cauliflowerlike lesion develops at the site of the initial inoculation, followed by the formation of skin plaques with scarring. Satellite lesions gradually arise from scratching and spread via the lymphatic system.2 Individual lesions may be thick and often develop secondary bacterial infections.

Chromoblastomycosis occurs worldwide but is most commonly seen in tropical and subtropical regions such as Central and South America, the Caribbean region, Africa, the Far East, and Australia, with Madagascar described as the most important focus in the world. Agricultural workers, farmers, and gardeners are at greater risk.

Therapy

Although natural immunity to fungal infections in general, and to chromoblastomycosis in particular, is not well understood, it is known to have no protective effect, as the disease has a very chronic and debilitating pattern of evolution.6 Traditional therapy includes continuous dosing with oral itraconazole or terbinafine, and there have been reports that itraconazole is a favorable drug for treatment of chromoblastomycosis, although there have also been reports on the development of resistance to itraconazole.7 In some cases, surgical removal of infected tissues is the most effective treatment. 5 Cryotherapy, topical heat therapy, systemic medications, and a combination of the above have been reported to be effective.7 Complications of chromoblastomycosis include elephantiasis, squamous cell carcinomas 3, and acral lentiginous melanoma.4

References

  1. Combating Fungal Infections: Problems and Remedy By Iqbal Ahmad, Mohammad Owais, Mohammed Shahid
  2. Clinical and Basic Immunodermatology edited by Anthony Gaspari, Stephen K. Tyring
  3. Imported Skin Diseases By William Richard Faber, Roderick J. Hay, B. Naafs
  4. HPV and Other Ifections Agents of Cancer by Hans Krueger, Richard Gallagher, Gavin Stuart, Dan Williams
  5. Clinical handbook of pediatric infectious disease By Russell W. Steele
  6. Humoral Immune Response in Chromoblastomycosis during and after Therapy P. Esterre, M. Jahevitra, and A. Andriantsimahavandy
  7. Chromoblastomycosis Caused by Phialophora richardsiae Young-Min Son, M.D. et al.



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