Hereditary complete deficiency of lactate dehydrogenase H-subunit

We report the second known case of a patient, a 45-year-old Japanese woman, with hereditary complete deficiency of lactate dehydrogenase (LDH; EC 1.1.1.27) H-subunit. Total LDH activity in her serum was abnormally low (35 U/L, normal reference interval 195-360). LDH activity in her erythrocytes was also low, but all the other glycolytic enzyme activities in her erythrocytes were within normal limits. Electrophoresis of her serum, erythrocytes, lymphocytes, thrombocytes, and saliva showed only one band, the LDH M4 isoenzyme. LDH activities in her saliva and lymphocytes exceeded the reference interval. Her erythrocytes contained fructose 1,6-diphosphate 26 mumol/L (normal range 4-13), dihydroxyacetone phosphate 75 mumol/L (normal range 8-22), glyceraldehyde 3-phosphate 57 mumol/L (normal range 4-14), and pyruvate 45 mumol/L (normal range 31-63). The family study of three generations showed that this deficiency was inherited in an autosomal recessive mode.