The relationship between glucose-6-phosphate dehydrogenase deficiency and cataracts in Sardinia. An epidemiological and biochemical study.

The Italian island of Sardina occupies an important position on the map of glucose-6-phosphate dehydrogenase (G6PD)-deficiency distribution throughout the world, since in this region the condition is particularly frequent and severe (erythrocytes show only 0-7% of G6PD normal activity, while people result affect up to 35% depending on the district). In order to investigate the relationship between the deficiency of G6PD in erythrocytes and in lens, and cataractogenesis, we studied 2125 idiopathic cataractous and non-cataractous subjects, both G6PD-deficient and normal, males and females. Parameters investigated included incidence, distribution and type of cataracts, age at the moment of the first observation, geographical provenance, and G6PD activity in erythrocytes. Moreover, G6PD activity and glutathione (GSSG)-reducing activity was assessed in cataractous lenses obtained from deficient and normal individuals. G6PD deficiency was found to be significantly more frequent in males of the age-group 40-49 years (P = 0.025), while the frequency of G6PD deficiency was decisively lower in the older age-groups. In females, mainly heterozygotes, no evidence of such a relation was found. Cataractous lenses obtained from male patients with no G6PD activity in erythrocytes showed undetectable levels of G6PD activity, and lowered, but not extinguished, levels of GSSG-reducing activity. Cataractous lenses from heterozygous females showed intermediate levels of G6PD activity and GSSG-reducing activity. A preliminary study of 182 diabetic, G6PD-deficient and non-deficient subjects, failed to demonstrate that Sardinian variants of G6PD deficiency provide protection against cataract formation in diabetic patients.