BRANCHING ENZYME IN ERYTHROCYTES: DETECTION OF TYPE IV GLYCOGENOSIS HETEROZYGOTES

Abstract

A 2 year-old boy with hepatosplenomegaly and muscular hypotonia showed a deficient branching enzyme activity (BE) in fibroblasts (diagnosis confirmed by B. Brown, USA). We have investigated BE in erythrocytes (erys) by determination of phosphates released from glucose-1-p in the mixture containing phosphorylase. BE in erys was well measureable as debranching enzyme and phosphorylases. BE in erys of the patient was deficient (0-0.2 umol/min/g Hb vs. 4-16 in controls, n=75). Glycogen was not elevated in erys of the patient(4 mg/ dL; normal, 0-10). BE in erys from his mother was app. 50 % of the normal range (2.92). Type IV glycogenosis was suspected by the pathological examination in a female patient who died of the respiratory distress syndrome 1 day after birth. BE in erys of his parents was 2.55 and 2.22 and in fibroblasts 0.14 and 0.35 umol/min/mg protein respectively (control fibroblasts, 0.4-1.4, n=8). These results show that easily accessible heparinized blood is an excellent source for the homo-and heterozygote detection of type IV glycogenosis.