Sex limited ahaptoglobinaemia.

Hypohaptoglobinaemia and ahaptoglobinaemia occurred in three generations, mainly to male members of a family. Also small amounts of haptoglobin were detected in most of the female relatives. Haemolytic anaemia seemed likely and the glucose 6 phosphate dehydrogenase (G.6.P.D.) activity was normal. The probable genotype of these apparently healthy individuals was Hp2/Hp2. These preliminary data might suggest a defect in control of gene expression by steroid hormones.