Haemolytic anaemias occur when the rate of red-cell breakdown is increased and exceeds the marrow’s capacity to generate new cells. Increased red-cell destruction, or haemolysis, may reflect a broad range of disorders. Some involve intrinsic defects in the red cell itself; in others, the red cells are normal but are subjected to external factors which lead to premature destruction. Many of the intrinsic defects are due to inherited disorders affecting the red-cell membrane, its enzymes, or haemoglobin. The marrow can normally compensate for moderate haemolysis by increasing red-cell production up to tenfold. Only when haemolysis is severe and the red-cell lifespan is reduced to less than about 15 days, or the marrow is unable to compensate, will anaemia occur. This chapter addresses the diagnosis, investigation, and management of haemolytic anaemias, including hereditary spherocytosis, paroxysmal nocturnal haemoglobinuria, glucose-6-phosphate dehydrogenase deficiency, haemoglobinopathies, and mechanical and immune haemolytic anaemias.
Red cell NADP+ and NADPH in glucose-6-phosphate dehydrogenase deficiency.