| • | the normally functioning hexose monophosphate shunt protects the red cell and its contents from oxidative agents within the cell (hydrogen peroxide, free radicals, etc…) |
| • | G6PD is the most commonly deficient enzyme in this system |
| • | there have been reported over 150 variants or isoenzymes of G6PD |
| • | in the US the most common variant causing problems is A- which is seen in American blacks |
| • | like all G6PD enzymes, it is sex linked |
| • | the A- variant has normal activity in young cells but because of its instability loses activity in old cells |
| • | a steady state condition can thus occur where the amount of hemolysis is compensated by production of young cells |
| • | since G6PD is a sex linked, deficiency is fully expressed in males and variably expressed in females secondary to the Lyon effect |
| • | oxidant drugs are the usual cause of destruction but any stress (e.g. infection ) can produce it |
| • | oxidation causes the denaturation of intracellular components which precipitate as Heinz bodies, the morphologic hallmark of this disease |
|