Tropical splenomegaly syndrome in a Rwandan kindred in Uganda.

Twenty members of an immigrant Rwandan kindred were all found to have tropical splenomegaly syndrome compared with 29 out of 50 matched neighbour controls. Splenomegaly among the controls tended to cluster within families. IgM levels were significantly raised in the kindred compared with the control subjects without splenomegaly but were similar to those of neighbours with splenic enlargement. We advance a hypothesis that tropical splenomegaly syndrome results from the production of circulating immune complexes in individuals genetically predisposed to produce an IgM antibody response.