G6PD hillbrow: a new variant of glucose-6-phosphate dehydrogenase associated with drug-induced haemolytic anaemia.

A new genetic variant of the red cell enzyme glucose-6-phosphate dehydrogenase is described. It was observed in a patient presenting with severe haemolytic anaemia and renal failure following ingestion of an overdose of Beserol (paracetamol and chlormezanone). The enzyme in the red cell had 12% of the activity of a normal B+ control, but only slightly lower activity in the kidney compared with a normal control. The red cell enzyme showed normal electrophoretic mobility and thermostability, a biphasic pH optimum curve, higher than normal utilization of the substrate analogues 2-deoxy-glucose-6-phosphate and deamino-NADP, and lower than normal Michaelis constants for both substrates, glucose-6-phosphate and NADP. The enzyme was strongly inhibited in vitro by high concentrations of paracetamol and chlormezanone. The extent of inhibition was similar to that for the enzyme from a normal B+ individual.