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We report on two Japanese brothers with hereditary deficiency in gamma-glutamyl transpeptidase. The propositus was 48 years old when he first visited our medical center and had a 51-year-old brother. The brothers were both tall and slender and had long limbs; the younger was diagnosed as having Marfan syndrome. Both patients both showed a tendency to retarded mental development. gamma-Glutamyltranspeptidase activity was below the detection limit of 1 IU/L in both patients. Glutathionaemia and glutathionuria were evident in both brothers. The analyses of sulphydryl compounds in the plasma (and serum for certain test items) and urine indicated high concentrations of glutathione, gamma-glutamylcysteine, cysteine and cysteinylglycine. Urine amino acid analysis on an automatic analyser showed a slightly increased excretion of cystine and a large peak in the citrulline position due, at least in part, to thio-compounds.

A mentally retarded young woman with severe behaviour problems was found to excrete large amounts of glutathione due to a generalized gamma-glutamyl transpeptidase deficiency. As in the only other case described in detail, plasma levels and renal reabsorption of the amino acids were normal. In the parents' urine, plasma and leukocytes, enzyme activity was normal but in their cultured fibroblasts it was below the minimum for the control range. An autosomal recessive mode of inheritance is suggested. The implications of these findings for possible role of the gamma-glutamyl cycle in amino acid transport are briefly discussed.

In a therapeutic trial, the effect of short-term low-dosage N-acetylcysteine supplementation on glutathione metabolism was investigated in two patients with hereditary glutathione deficiency (5-oxoprolinuria). Clinical and neurophysiological examinations of the patients indicated progressive neurological damage. The pretreatment concentrations of total and free glutathione in leukocytes were 15-20% of normal, whereas the corresponding gamma-glutamylcysteine levels were increased. In plasma, the glutathione concentrations were similarly decreased, but no gamma-glutamylcysteine was detected. Total glutathione in erythrocytes was markedly decreased. Low urinary excretion of cysteinylglycine, cyst(e)ine, taurine, N-acetylcysteine, mercaptolactate and mercaptoacetate and reduced leukocyte taurine levels constituted additional evidence of decreased intracellular availability of cysteine, i.e. glutathione. Oral supplementation with N-acetylcysteine (5 mg/kg x 3/day) had no effect on acid-base balance, erythrocyte glutathione levels or 5-oxoproline concentrations in plasma and urine. In leukocytes, the glutathione concentrations were increased by 20-30%, whereas the gamma-glutamylcysteine levels were essentially unaltered. In parallel, the urinary excretion of cysteinylglycine was increased and the leukocyte levels and urinary outputs of sulphur amino acids were restored. No side-effects of the treatment were noted. The results indicate that N-acetylcysteine may be of value in increasing the low intracellular glutathione concentrations and cysteine availability in patients with hereditary glutathione synthetase deficiency.