G6PD Deficiency

G6PD Deficiency is a hereditary abnormality in the activity of an erythrocyte (red blood cell) enzyme. This enzyme, glucose-6-phosphate dehydrogenase (G-6-PD), is essential for assuring a normal life span for red blood cells, and for oxidizing processes. This enzyme deficiency may provoke the sudden destruction of red blood cells and lead to hemolytic anemia with jaundice following the intake of contraindicated substances.

The structure of G-6-PD is carried on the X chromosome: As stated by Ernest Beutler, M.D., “in females, only one of the two X chromosomes in each cell is active; consequently, female heterozygotes for G-6-PD deficiency have two populations of red cells; deficient cells and normal cells.”

The deficit is most prevalent among Kurdish Jews (up to 70% of the population) but is also common in Africa (affecting up to 20% of the population), around the Mediterranean (4% – 30%) and southeast Asia. Please note that there are more than 400 genetic variants of the deficiency.

 

Some variants are not reliably detectable on the Beutler Test. 

 

The diagnosis of G6PD deficiency is commonly made, by a rapid fluorescent spot test detecting the generation of NADPH from NADP.

The test is positive if the blood spot fails to fluoresce under ultraviolet light.

In patients who have recently hemolyzed, the test results for G6PD deficiency may be falsely negative because the older red blood cells with a higher enzyme deficiency have been hemolyzed (destroyed).

Young red blood cells have normal or near-normal enzyme activity even in G6PD deficiency.

Female heterozygotes (carriers) may be hard to diagnose because of X-chromosome mosaicism (being composed of cells of two genetically different types) leading to a partial deficiency that will not be detected reliably with screening tests.

http://www.aafp.org/afp/2005/1001/p1277.html

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