GSTM1 and pyruvate kinase deficiency of red cells: High performance liquid chromatography (HPLC) rejected the co-inheritance of an hemoglobinopathy, but the measurement of RBC enzyme activities showed a decrease of PK activity (7.5 IU/g Hb, Normal range: 8.4–15.2) and of the PK/HK ratio (6.3, normal range: 7.2–15.6), suggesting the existence of a heterozygous PK deficiency (PKD).