Spleen weights in Uganda with reference to malaria, migration and idiopathic tropical splenomegaly

Abstract

In a study of spleen weights at autopsy in Mulago Hospital it has been shown that splenomegaly is more usual than a “normal” spleen, and gross splenomegaly (idiopathic tropical splenomegaly) appears to represent the extreme of a distribution curve skewed towards the heavier spleens. Subjects originating from areas of low malarial endemicity have in general far heavier spleens than those indigenous to this area of high malarial endemicity. In the groups subject to marked splenic enlargement, cirrhosis of the liver greatly increases this tendency but it does not do so to the same degree in the indigenous subjects. Males tend to have a higher frequency of large spleens than females. Analysis of spleen weights by age shows that from 15–24 years of age onwards the immigrant groups have very much heavier spleens than the indigenous people. This is the age at which most immigrants come to Buganda for the first time and this adds circumstantial support to the concept of an exaggerated response to malaria in non-immune or partially-immune subjects. Studies of the immunological constitution of Rwanda and Ganda subjects living in the Kampala region reveal marked differences. The Rwanda have higher malarial antibody titres and these are associated with IgM levels and high frequencies of autoantibodies to several tissues. Idiopathic tropical splenomegaly is held to represent an exaggerated immunological response to malaria in individuals from relatively malaria-free areas who are first exposed to the parasite in early adult life or in individuals exposed to malaria under unstable conditions of transmission and infection.