Hb K Woolwich the cause of a thalassaemia.

Abstract

IN general terms, heterozygotes for β thalassaemia have a moderate degree of microcytosis associated with an elevated red cell count, a reduced mean cell volume (MCV) and mean cell haemoglobin (MCH) and a normal, or near normal, mean cell haemoglobin concentration (MCHC). The chief diagnostic parameter of the heterozygous state is, however, the elevated Hb A2 level which accompanies the condition. This does not occur in other haemoglobinopathies with the exception of those associated with unstable haemoglobins and some heterozygotes for Hb S (ref. 1) and Hb C (ref. 2). At the molecular level β thalassaemia is associated with an imbalance of globin chain synthesis during erythroid cell maturation, as a result of defective β chain synthesis. The extent of the defect parallels the severity of the thalassaemia, ranging from a reduction in the amount of product from the affected β chain locus (β+ thal) to no product (β0 thal). In all cases of β+ thal so investigated, the β chains produced by the affected gene have been indistinguishable from normal βA chains.