Abstract
Sweden has 10.2 million inhabitants and more than 2.4 million have a foreign background. A substantial number of immigrants come from countries where glucose-6-phosphate dehydrogenase deficiency (G6PDD) is frequent. The total birth rate annually in Sweden is approximately 117,000 and newborn screening is centralized to one laboratory. We determined glucose-6-phosphate dehydrogenase (G6PD) activity in 10,098 dried blood spot samples (DBS) from the whole country with a fluorometric assay (LabSystems Diagnostics Oy, Finland). The first 5451 samples were anonymised and run as singletons, whilst the following 4647 samples were coded. Enzyme activity ≤40% of the mean of the day was found in 58 samples (1/170) and among these, 29 had activities ≤10% (1/350). Twenty-nine samples with residual activities between 2–39% in the coded cohort were subjected to Sanger sequencing. Disease-causing variants were identified in 26 out of 29 infants, of which six were girls. In three patients, we did not find any disease-causing variants, although two patients were hemizygous for the known polymorphisms c.1311T>C and c.1365-13C>T. The most common disease-causing variant found in 15 of the 29 samples (12 hemizygotes, two heterozygotes, one homozygote) was the Mediterranean mutation, c.563C>T (p.(Ser188Phe)) in exon 6. G6PDD is thus a surprisingly prevalent disorder in Sweden.
Highlights
Glucose-6-phosphate dehydrogenase (G6PD, E.C.1.1.1.49) is a key enzyme in the pentose phosphate pathway, which produces ribose-5-phosphate
The assay measures the formation of NADPH, when NADP+ is reduced by the glucose-6-phosphate dehydrogenase (G6PD) enzyme in the presence of glucose-6-phosphate (Scheme 1)
Our results indicate that 1/350 newborn infants have a glucose-6-phosphate dehydrogenase deficiency (G6PDD) with an enzyme activity of ≤10% of normal
Summary
Glucose-6-phosphate dehydrogenase (G6PD, E.C.1.1.1.49) is a key enzyme in the pentose phosphate pathway, which produces ribose-5-phosphate. G6PD is extremely important for the reduction of nicotinamide adenine dinucleotide phosphate (NADP+) to NADPH + H+. It is a housekeeping enzyme important for the control of oxidative stress, especially in red blood cells, which lack nucleus and mitochondria. Patients with glucose-6-phosphate dehydrogenase deficiency (G6PDD, OMIM_305900) are asymptomatic unless they have a very low residual activity or are exposed to some specific triggers, including certain medicines, infections or fava beans (Vicia faba), the latter being the most common trigger [1]. The clinical presentation of the disorder is dependent on the level of residual activity of the enzyme and the load of the trigger. There is no cure for the disorder, but once diagnosed, the patients can avoid known triggers and be treated promptly when they get symptoms
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