Clin Genet 1999: 55: 444–449 Printed in Ireland. All rights reser6ed Original Article Clinical, biochemical, and molecular characterization of patients with glutathione synthetase deficiency Al-Jishi E, Meyer BF, Rashed MS, Al-Essa M, Al-Hamed MH, Sakati N, Sanjad S, Ozand PT, Kambouris M. Clinical, biochemical, and molecular characterization of patients with glutathione synthetase defi- ciency. Clin Genet 1999: 55: 444–449. © Munksgaard, 1999 Pyroglutamic aciduria (5-oxoprolinuria) is a rare autosomal recessive disorder caused by either glutathione synthetase deficiency (GSSD) or 5-oxoprolinase deficiency. GSSD results in low glutathione levels in erythrocytes and may present with hemolytic anemia alone or together with pyroglutamic aciduria, metabolic acidosis, and CNS damage. Five patients with pyroglutamic aciduria were studied. All presented with hemolytic anemia and metabolic acidosis. Two (brothers) also had Fan- coni nephropathy, which is not seen in pyroglutamic aciduria. Molecu- lar analyses of the GSS gene was performed in 3 patients. RT-PCR and heteroduplex analysis identified a homozygous deletion in 1 patient and a homozygous mutation in 2 others (brothers with Fanconi nephropathy). Sequencing of glutathione synthetase (GSS) cDNA from the first patient showed a 141-bp deletion corresponding to the entire exon 4, whilst the corresponding genomic DNA showed a G 491 A homozygous splice site mutation. Sequencing of GSS cDNA from the Fanconi nephropathy patients showed a C 847 T [ARG 283 CYS] mu- tation in exon 9. E Al-Jishi a , BF Meyer a , MS Rashed a , M Al-Essa a , MH Al-Hamed a , N Sakati a , S Sanjad a , PT Ozand a and M Kambouris a,b a King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia, b Yale University School of Medicine, New Haven, CT, USA Key words: Fanconi nephropathy – glutathione synthetase deficiency – heteroduplex analysis – pyroglutamic aciduria – RT-PCR Corresponding author: Marios Kambouris, PhD, FACMG, King Faisal Specialist Hospi- tal and Research Center, P.O. Box 3354 – MBC c03, Riyadh 11211, Saudi Arabia. Tel.: +966-1-442-6302; fax: +966-1-442- 7858; e-mail: marios.kambouris@yale.edu Received 10 February 1999, revised and accepted for publication 10 March 1999 Glutathione synthetase deficiency (GSSD) is a rare autosomal recessive metabolic disease. Thus far, GSSD has been described in 40 patients from 36 families. The severe form of the disease is charac- terized by acute metabolic acidosis, usually present in the neonatal period, hemolytic anemia, and pro- gressive encephalopathy. Glutathione synthetase (GSS) is an essential enzyme in the pathway of glutathione synthesis (GS). Glutathione deficiency in the erythrocytes accounts for the hemolytic ane- mia (1), and in the CNS for the progressive en- cephalopathy (2). Under normal physiologic conditions, glutathione regulates its own synthesis by feedback inhibition of GS; when glutathione is reduced there is increased formation of g-glutamyl- cysteine, which is readily converted to pyroglu- tamic acid through the action of g-glutamylcyclotransferase. This leads to increased accumulation of 5-oxoproline in the plasma and urine, leading to severe metabolic acidosis due to the strongly acidic nature of this compound. In a milder form of the disease, the deficiency appears to be restricted to erythrocytes (3). In this condition, a compensated hemolytic disease is ob- served without neurologic involvement. This milder form can be readily differentiated since it does not cause pyroglutamic aciduria. Only one active GSS gene exists in the human genome and is located on chromosome 20q11.2 (4). The molecular basis of GSSD has recently been described (5, 6). In one study (5), seven mutations at the GSS locus on six alleles were identified: one splice site mutation, two deletions, and four mis- sense mutations. In a second study (6), 13 muta- tions were identified in 9 patients. Four patients were compound heterozygotes and 2 were ho- mozygous for their respective mutations. In 3 pa- tients, only one pathogenic mutation was identified, while the other remained unknown. This study describes the clinical and biochemical features in 5 patients with GSSD, and the associ- 444