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Glucose 6-phosphate dehydrogenase variants: Gd (+) Alexandra associated with neonatal jaundice and Gd (-) Camperdown
Insights
Two novel Glucose-6-Phosphate Dehydrogenase (G6PD) variants, Gd(+) Alexandra and Gd(-) Camperdown, were identified in patients with unusual clinical presentations. These cases highlight the importance of characterizing G6PD variants for understanding diverse G6PD deficiency manifestations.
Area of Science:
- Biochemistry
- Genetics
- Clinical Medicine
Background:
- Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency is a common genetic disorder.
- Clinical manifestations of G6PD deficiency can vary widely.
- Identification of novel G6PD variants is crucial for understanding enzyme function and disease pathology.
Observation:
- Two male patients presented with distinct and previously undescribed clinical features associated with G6PD deficiency.
- The first patient, of Italian descent, experienced severe neonatal jaundice linked to maternal broad bean (Vicia fava) consumption, with a variant designated Gd(+) Alexandra.
- The second patient, of Maltese descent, presented with bilateral lamellar cataracts and was identified as G6PD deficient with a variant designated Gd(-) Camperdown.
Findings:
- Biochemical characterization revealed unique features for both Gd(+) Alexandra and Gd(-) Camperdown variants.
- The Gd(+) Alexandra variant showed a more severe enzymatic defect in the neonatal period compared to adolescence.
- The Gd(-) Camperdown variant exhibited approximately 15% of normal enzyme activity, with distinct biochemical characteristics.
Implications:
- The discovery of these new G6PD variants expands the known spectrum of G6PD deficiency.
- The association in the second patient suggests a potential link between G6PD deficiency and cataract formation under specific conditions.
- Characterizing mutant G6PD enzymes is essential for interpreting unexpected clinical and laboratory findings in G6PD deficiency.
Abstract:
Two male subjects are described, with unusual clinical presentations and with hitherto undescribed G6PD variants. The first, of Italian extraction, suffered from severe neonatal jaundice following maternal ingestion of fresh broad beans (Vicia fava) both prenatally and postnatally: the expression of the enzymatic defect was much more severe in the neonatal period than on retesting in adolescence, when biochemical characterization showed unique features which justify designation as a new variant Gd(+) Alexandra. The second patient, a boy of Maltese extraction who was found to have bilateral lamellar cataracts at the age of 4 years, was identified as G6PD deficient only as a result of a survey of children of Mediterranean origin with unexplained cataract formation; he has approximately 15% of normal enzyme activity, with another unique combination of biochemical characteristics which has led to its designation as Gd(-) Camperdown. Although this association may be coincidental, it prompts further attention to the possibility that under certain circumstances G6PD deficiency may favor cataract formation. The two cases illustrate the value of characterization of the mutant enzyme whenever unexpected clinical or laboratory results are obtained.