Pyruvate kinase deficiency is the most common defect of the glycolytic pathway. It is characterized by a highly variable degree of chronic non-spherocytic hemolytic anemia, with various degrees of intensity.

PK deficiency is an autosomal recessive disease caused by mutations in the PKLR gene on chromosome 1q21. This gene encodes pyruvate kinase that catalyzes the transphosphorylation of phohsphoenolpyruvate into pyruvate and ATP, which is the rate-limiting step of glycolysis. Also, this is one of two glycolytic reactions in the erythrocyte that result in the production of ATP.