Cutaneous leishmaniasis is the most common form of leishmaniasis. It is a skin infection caused by a single-celled parasite that is transmitted by sand-fly bites. There are about 20 species of Leishmania that may cause cutaneous leishmaniasis.

Epidemiology

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Cutaneous leishmaniasis endemic to many parts of the world. Around twenty different species of Leishmania parasite are capable of infecting man. The distribution of cutaneous leishmaniasis is very tightly linked to geography.

Pathology

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Promastigotes of leishmania are transmitted to human skin by the bite of a sandfly. Leishmania then invades human T-cells and replicates intracellularly.

A raised, red lesion develops at the site of the bite (often weeks or sometimes years afterwards). The lesion then ulcerates and may become secondarily infected with bacteria. In many species (for example, L. major) the lesion often spontaneously heals with atrophy scarring. In some species (for example, L. viannia braziliensis) the lesion may spontaneously heal with scarring, but then re-appear elsewhere (especially as destructive mucocutaneous lesions). Lesions of other leishmania species may spontaneously heal and then re-appear as satellite lesions around the site of the original lesion, or along the route of lymphatic drainage.

Post kala-azar dermal leishmaniasis

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Species that usually cause visceral leishmaniasis (for example, L. infantum or L. donovani) after full and adequate treatment may then re-appear as multiple raised skin lesions called "post kala-azar dermal leishmaniasis". This is not a result of inadequate treatment of visceral leishmaniasis. The skin lesions will respond to retreatment.

Mucocutaneous leishmaniasis

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Mucocutaneous leishmaniasis is the most feared form of cutaneous leishmaniasis because it produces destructive and disfiguring lesions of the face. it is most often caused by Leishmania viannia braziliensis but other leishmania species have rarely been described.

Treatment

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The evidence for optimal treatment of cutaneous leishmaniasis is patchy. Treatments that work for one species of leishmania may not work for another; it is recommended that advice of a tropical medicine or geographical medicine specialist be sought. Ideally, every effort should be made to establish the species of leishmania by molecular techniques. In the setting of a developing country, there is often only one species present in a particular locality, so it is usually unnecessary to speciate every infection. Unfortunately, leishmaniasis is an orphan disease, and almost all the current treatment options are toxic, with significant side-effects.

Secondary bacterial infection (especially with Staphylococcus aureus) is common and may require antibiotics.

Leishmania major

Treatment of L. major infections is unnecessary because the lesions will usually resolve spontaneously after some months. Fluconazole has been shown to reduce the time to resolution.

Leishmania (Vianna) braziliensis

Treatment is mandatory because of the risk of developing mucocutaneous lesions. Amphotericin and pentavalent antimonials remain the treatments of choice.

Diseases