infectious diseases
Leishmaniasis
Pathophysiology of Leishmaniasis
After inoculation by a sand fly, extracellular promastigotes are phagocytized by host macrophages; inside these cells, they transform into amastigotes. The parasites may remain localized in the skin or spread to the mucosa of the nasopharynx or disseminate to bone marrow, the spleen, the liver, and occasionally other organs, resulting in 3 major clinical forms of leishmaniasis: Cutaneous Mucosal Visceral Cutaneous leishmaniasisis also known as oriental or tropical sore, Delhi or Aleppo boil, uta or chiclero ulcer, or forest yaws. The major causative species are L. majorandL. tropicain southern Europe, Asia, and Africa L. mexicanaand related species in Mexico and Central and South America L. braziliensisand related species in Central and South America Cases have occurred among US military personnel serving in Iraq and Afghanistan and among travelers to endemic areas in Central and South America, Israel, and elsewhere. Uncommonly,L. braziliensisspreads widely in the skin causing disseminated cutaneous leishmaniasis. Mucosal leishmaniasis(espundia) is caused mainly byL. braziliensisbut occasionally by otherLeishmaniaspecies. The parasites are thought to spread from the initial skin lesion through the lymphatics and blood to nasopharyngeal tissues. Symptoms and signs of mucosal leishmaniasis typically develop months to years after the appearance of the skin lesion. Visceral leishmaniasis(kala-azar, Dumdum fever) is typically caused byL. donovaniorL. infantum(previously calledL. chagasiin Latin America) and occurs in India, Africa (particularly the Sudan), Central Asia, the Mediterranean basin, South and Central America, and infrequently China. Most cases occur in northeastern India. Parasites disseminate from the site of the sand fly bite in the skin to regional lymph nodes, the spleen, the liver, and bone marrow and cause systemic symptoms. Subclinical infections are common; only a minority of infected patients develop progressive visceral disease. Symptomatic infection withL. infantumis more common among children than adults. Visceral leishmaniasis is an opportunistic infection in patients with AIDS or other immunocompromising conditions. 