Tropical splenomegaly syndrome: long-term proguanil therapy correlated with spleen size, serum IgM, and lymphocyte transformation.

Forty-three patients with an initial diagnosis of tropical splenomegaly syndrome were placed on long-term proguanil therapy. All patients who failed to respond to proguanil and who were adequately followed up developed identifiable disease, usually malignant lymphoma or chronic lymphatic leukaemia. In patients who responded to proguanil IgM values were always very high and phytohaemagglutinin (P.H.A.)-lymphocyte-transformation scores were always normal before treatment was started. In patients who failed to respond IgM values were within the normal range or below, while P.H.A.-lymphocyte-transformation scores were abnormally low. During proguanil treatment IgM values fell gradually, closely paralleling the decrease in spleen size.