visceral leishmaniasis

Definition: Kala-azar (KA) is a life-threatening protozoal disease caused by Leishmania parasites (L. donovani, L. chagasi, and L. infantum). The disease, which is also called "visceral leishmaniasis," is prevalent in Africa, South America, Asia, and the Mediterranean basin.

Images

 Visceral leishmaniasis

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In visceral leishmaniasis, L. donovani or L. chagasi parasites invade macrophages throughout the mononuclear phagocyte system and cause severe systemic disease marked by hepatosplenomegaly, lymphadenopathy, pancytopenia, fever, and weight loss.

The spleen may weigh as much as 3 kg, and the lymph nodes may measure 5 cm in diameter. Phagocytic cells are enlarged and filled with Leishmania, many plasma cells are present, and the normal architecture of the spleen is obscured.

In the late stages, the liver becomes increasingly fibrotic. Phagocytic cells crowd the bone marrow and also may be found in the lungs, gastrointestinal tract, kidneys, pancreas, and testes.

Often there is hyperpigmentation of the skin in the extremities, which is why the disease is called kala-azar or "black fever" in Hindi. In the kidneys, there may be an immune complex-mediated mesangioproliferative glomerulonephritis, and in advanced cases, there may be amyloid deposition.

The overloading of phagocytic cells with parasites predisposes the patients to bacterial infections, the usual cause of death. Hemorrhages related to thrombocytopenia may also be fatal.

Susceptibility

 locus 22q12 (14557985)

References

 Blackwell JM, Mohamed HS, Ibrahim ME. Genetics and visceral leishmaniasis in the Sudan: seeking a link. Trends Parasitol. 2004 Jun;20(6):268-74. PMID: 15147677