Sickle cell disease in permanent residents of mountain and low altitudes in Saudi Arabia.

Report of a comparative study of sickle cell disease in permanent residents of mountain and low altitudes in south-western Saudi Arabia. The ambient oxygen tensions at these altitudes are 14 and 19 kPa (112 and 144 mmHg) respectively. The frequencies of sicklaemic-related illness requiring medical intervention, and hospitalisation due to crisis and complications of the disease, were about twice as great in highlanders as in lowlanders. The incidence and severity of the complications were similar in both locations. No splenic syndrome was observed in those with the disease or trait in either location. Haemoglobin concentration was 10% greater in mountain normals than in their lowland counterparts; the corresponding figure for sicklers was 5%. Erythrocyte 2,3 diphosphoglycerate concentration was 13% greater in mountain than valley patients; the corresponding figure for normals was 4%. We propose that the elevated diphosphoglycerate in mountain patients might contribute to their higher frequency of sicklaemic illness as well as partially blunting their erythropoietic drive.