Haemoglobinopathies and malaria: new approaches to an old hypothesis.

It is almost 40 years since Haldane proposed that high frequencies of thalassaemia and other hoemoglobinopathies might result because these genetic disorders conferred some protection against malaria In the intervening years convincing clinical, epidemiological and in vitro data have been produced to support this 'malaria hypothesis' for haemoglobin S. However, for the numerous other genetic disorders of haemoglobin that are suspected to have been selected in this way it has been much more difficult to provide clearcut evidence. For example, in the case of beta-thalassaemia some but not all epidemiological studies support the hypothesis, while in vitro studies have failed to demonstrate any impairment of either invasion or growth of P. falciparum in affected red cells under physiological conditions.