5-Oxoprolinase deficiency: report of the first human OPLAH mutation.

Gamma-glutamyl cycle is a six-enzyme cycle that represents the primary pathway for glutathione synthesis and degradation. 5-Oxoprolinase deficiency is an extremely rare disorder of the gamma-glutamyl cycle with only eight patients reported to date. Debate continues as to whether this is a benign biochemical defect because of the heterogeneity of the clinical presentation which ranges from normal to significant neurological involvement. Here, we report the first molecularly characterized patients with 5-oxoprolinase deficiency due to a mutation in OPLAH (which encodes 5-oxoprolinase). The largely benign clinical course of the patients described herein despite persistent 5-oxoprolinuria highlights the importance of establishing a molecular diagnosis in the few cases with abnormal neurological outcome to exclude potentially overlapping biochemical defects and to explore potential genotype/phenotype correlation.