Frequency of glucose-6-phosphate dehydrogenase deficiency in relation to altitude: a malaria hypothesis.

Genetic markers have recently been found to be much more polymorphic than expected. Such extensive human polymorphisms may be partly explained by a number of genetic and environmental factors, including infectious diseases. Malaria, which was very widespread in the past and still poses a problem in many countries today, is a good candidate for research. The association between malaria and glucose-6-phosphate dehydrogenase (G6PD) deficiency is well-known, but more should be done to determine the mechanisms responsible for this positive correlation and to confirm that malaria is a strong selective factor for many other genotypes also. The present paper refers to a WHO project on genetic markers and susceptibility to infectious diseases, which is concerned mainly with G6PD deficiency and the following genetic markers: haemoglobinopathies, including the beta-thalassaemia trait and ABO, Rh, MN, Duffy, secretory types (Ss), and human leukocyte antigens (HLA). Since malaria was eradicated in Bulgaria many years ago, human populations from this country, living at different altitudes above sea-level, were used as a model for analysis of the malaria hypothesis. The data for G6PD deficiency confirm that malaria was a selective factor in lowland areas where malaria infection was more frequent in the past. It is, moreover, apparent that in addition to malaria some other factors also play a selective role.