LAUSR

Over the past few years, the inherited disorders of erythrocyte metabolism have been the object of intensive research resulting in a better understanding of their molecular basis.1 Pyruvate kinase (PK) deficiency is the most common cause of congenital non-spherocytic chronic hemolytic anemia and is the result of an erythrocyte enzyme defect. It is an autosomal recessive condition caused by a deficiency of erythrocytic PK. Although the gene frequency for PK deficiency is far lower than that for glucose-6-phosphate dehydrogenase (G6PD) deficiency, the vast majority of patients inheriting G6PD deficiency never suffer acute or chronic hemolysis, whereas chronic hemolysis of variable severity is common in those with PK deficiency.1,2 PK deficiency is an extremely rare disorder; the prevalence of this deficiency is unknown. The PK-catalyzed reaction is the second ATP-generating step of the glycolytic pathway and is of particular importance in energy production, yielding nearly 50% of the total ATP. PK enzymes consist of several isoforms. They are products of two distinct genes: the M (muscle) gene is expressed in muscles, the brain, white blood cells, and platelets; it is located on chromosome 15q22 and the M1 and M2 isoforms are the result of a differential processing of this single gene transcript; and the LR gene on chromosome