G6PD Deficiency

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is an X-linked inherited disorder caused by a genetic defect in the red blood cell enzyme G6PD, which serves to protect red blood cells from oxidative injury. It can cause jaundice in newborns as well as acute hemolytic anemia in patients exposed to oxidant stress exposures (see Table).

G6PD deficiency is mainly found in patients from Africa, the Mediterranean and Asia (see Map). The enzyme deficiency is usually more severe in patients of Mediterranean ancestry (Class II variant) than those of African ancestry (Class III variant).

Since it is an X-linked disorder, males are usually affected. This is why we recommend screening males only. Heterozygous female patients can have lower levels of G6PD but these are rarely clinically significant. However, all patients (men and women) with Plasmodium vivax or ovale malaria infections should be screened for G6PD deficiency before receiving primaquine (used to eradicate the dormant liver stages of these parasites).

 

DIAGNOSIS

G6PD testing can be performed either with a screening qualitative test (normal levels vs deficiency) or with a quantitative test (specific levels of G6PD activity). Testing algorithms may vary depending on the laboratory.

As per the World Health Organization, clinically significant G6PD deficiency is classified as enzyme activity <30% (<3 U/g Hb) in adults and children >12 months of age. Although some patients might have a mild deficiency (3-8 U/g Hb), they are usually less at risk of oxidative stress. These patients should still be counselled about potential oxidative stressors.

 

PATIENT EDUCATION

The diagnosis should be carefully explained to the patients. They should be told about the most common foods and drugs that can precipitate acute hemolysis (see Table). We also usually show them pictures of fava beans, mothballs and henna to make sure they avoid these substances.

Patient should be made aware of the symptoms of acute hemolysis and immediately seek medical help if they have any of them (mainly jaundice, pallor and dark urine).​

 

>> Refer to the Caring for Kids New to Canada website for more information on G6PD deficiency.