Genotype, enzyme activity, glutathione level, and clinical phenotype in patients with glutathione synthetase deficiency.
Glutathione synthetase (GS) deficiency is a rare autosomal recessive disorder. The clinical phenotype varies widely, and nearly 30 different mutations in the GSS gene have been identified. In the present study, genotype, enzyme activity, metabolite levels and clinical phenotype were evaluated in 41 patients from 33 families. From some of the patients, data on glutathione (GSH) levels and gamma-glutamylcysteine levels in cultured fibroblasts were also available. Twenty-seven different mutations were found: 14 missense, 9 splice, 2 deletions, 1 insertion and 1 nonsense mutation. Twenty-three patients were homozygous and 18 were compound heterozygous. The moderate and severe clinical phenotypes could not be distinguished based on enzyme activity, GSH or gamma-glutamylcysteine levels in cultured fibroblasts. However, in fibroblasts, the residual GS activity was correlated with the GSH level. All mutations causing frameshifts, premature stop codons or aberrant splicing were associated with moderate or severe clinical phenotypes including haemolytic anaemia, 5-oxoprolinuria, and (in several forms) neurodevelopmental signs. The data indicate that additional genetic or environmental factors modify at least the moderate and severe phenotypes and that the clinical classification given to the patients may be influenced by variation in follow-up. The type of mutation involved can, to some extent, predict a mild versus a more severe phenotype.
Njålsson
Runa
R
Division of Paediatrics, Department of Clinical Sciences, Karolinska Institute, Karolinska University Hospital Huddinge, Stockholm 14186, Sweden. runa.njalsson@mednut.ki.se
Ristoff
Ellinor
E
Carlsson
Katarina
K
Winkler
Andreas
A
Larsson
Agne
A
Norgren
Svante
S
D002478:Cells, Cultured; D004151:Dipeptides / Q000378:metabolism; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D005838:Genotype; D005978:Glutathione / Q000378:metabolism*; D005981:Glutathione Synthase / Q000172:deficiency*; D006801:Humans; D008297:Male; D009154:Mutation; D010641:Phenotype
D004151:Dipeptides; D005981:Glutathione Synthase; D005978:Glutathione; C017341:gamma-glutamylcysteine
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