Splenomegaly in Northern Nigeria.

Seventy five patients with large spleens were investigated in order to establish the causes of splenomegaly in Northern Nigeria, to define further the diagnostic criteria of tropical splenomegaly syndrome (TSS), and to study its pathogenesis. Investigations included examination of liver biopsy, bone marrow cytology, lymphocyte response to phytohaemagglutinin (PHA), serum immunoglobulins and complement, and the presence of immunoglobulin and complement fixed in Kupffer cells. Thirty patients had TSS, five chronic lymphatic leukaemia (CLL), four a syndrome of gross lymphoid hyperplasia (GLH) distinct from TSS, CLL and the lymphomas, and twenty three miscellaneous conventional diseases. In thirteen cases no definite diagnosis could be established. TSS was found to be predominantly a disease of female Fulani cattle herders. Its essential characteristics were splenomegaly in the presence of acquired immunity to malaria, a grossly raised serum IgM, a lowered serum complement, and the presence of IgM fixed in Kupffer cells. There was lymphoid hyperplasia in bone marrow, hepatic sinusoids and often blood which may be indistinguishable from that in CLL. Lymphocytes undergo normal blastogenesis to PHA. There was clinical and haematological response to proguanil therapy. Reticuloendothelial phagocytosis of IgM, probably as a complex, seems to be the essential feature of the condition. As it was impossible to identify early cases of TSS it is unclear whether IgM overproduction or phagocytosis of IgM complexes is the first stage of the disease. The precise nature of the association with malaria remains obscure. The diagnosis of CLL demanded the demonstration of an abnormally low immunoglobulin level and impaired lymphocyte responsiveness to PHA by blast transformation or 3H-thymidine incorporation, in addition to the usual haematological findings. The syndrome GLH occurred in multiparous Hausa women. It was characterised by intense lymphocytosis with active, PHA-responsive cells, and normal immunoglobulin levels. Patients responded to proguanil therapy. It is suggested that these patients have a depressed immune response to malaria, perhaps through repeated pregnancies, and to a leukaemogenic agent, both of which stimulate lymphocytosis. Antimalarial treatment at this stage may prevent the development of frank leukaemia or lymphoma. The usefulness of the various investigative procedures and the problem of managing the large number of undiagnosed cases are discussed.