Clinical picture, hyperreactive malaria splenomegaly (HMS)

Some adults have a very strong immunological reaction to P. falciparum infection. The level of IgM in the blood is very high. Due to the polyclonal immune stimulation, all kinds of auto-antibodies can appear. Immune complexes are formed, and are removed by the reticulo-endothelial system, which leads to splenomegaly and sometimes enlarged liver. In these individuals the spleen swells and also breaks down normal, unparasitised blood cells. The number of parasites is very low, but very high concentrations of anti-Plasmodium falciparum antibodies can be detected. The splenomegaly disappears after curative therapy with, e.g. quinine + tetracyclines followed by months or even years of adequate malaria chemoprophylaxis (impregnated mosquito net + efficient chemoprophylaxis in a malaria region), but recovery is very slow. In rare cases splenectomy is necessary. Steroids have no place in the treatment.

The disorder may be very similar to a certain indolent splenic lymphoma (e.g. splenic lymphoma with villous lymphocytes). The latter disorder is related to B-cell chronic lymphocytic leukaemia and occurs chiefly in elderly persons. The disease is often accompanied by significant cytogenetic abnormalities and monoclonal “villous” B-lymphocytes in the peripheral blood. It is likely that in HMS, excessive stimulation of the B-lymphocytes by malaria antigens increases the risk that oncogenic mutation may occur, followed by clonal growth of these cells. The extent to which this aetiopathogenetic mechanism is similar to the MALT lymphomas (mucosa-associated lymphoid tissue) which are sometimes seen in chronic infection with Helicobacter pylori, is unclear.

Category: Medicine Notes