Background: Age-related skewing of X-chromosome inactivation leading to glucose-6-phosphate dehydrogenase (G6PD) deficiency in elderly women in a population with prevalent G6PD gene mutations was investigated.
Methods: G6PD activity was measured biochemically. G6PD mutations were detected by polymerase chain reaction (PCR) and allele-specific extension, and analyzed by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry and Sequenom MassARRAY. X-chromosome inactivation was quantified by semiquantitative PCR for the HUMARA gene, before and after HpaII digestion.
Results: In 173 women (median age: 90 years; range, 80-107 years), 18 heterozygotes for G6PD mutations were identified. Three heterozygotes were G6PD deficient, owing to skewed X-chromosome inactivation affecting the wild-type allele. Fifteen heterozygotes, with skewing apparently affecting the mutant alleles, had normal but significantly lower G6PD levels. At 1.73%, G6PD deficiency was significantly more frequent than expected from population screening at birth.
Conclusion: Due to skewed X-chromosome inactivation, elderly women in populations with prevalent G6PD mutations are at risk of G6PD deficiency.