Hemoglobinopathies

Other Abnormalities

A wide variety of additional RBC abnormalities exist. Several of these are discussed below:

G6PD Deficiency

This genetic disorder arose in Africa. There is a deficiency of the enzyme glucose-6-phosphate dehydrogenase. This enzyme is involved in the hexose monophosphate shunt pathway that aids in generation of reduced glutathione within cells. Glutathione aids in protecting cells against oxidant injury. G6PD deficiency is probably present with some frequency because there are variants of this disorder that appear to provide some protection against malarial infection.

The G6PD gene is present on the X chromosome; thus, males are mainly affected. Persons with this disorder have RBC's that are prone to oxidative injury, especially the older RBC's. The RBC's are at increased risk for injury from certain drugs and toxins, such as primaquine or phenacetin, that are oxidants.

RBC's are more prone to hemolyze. Heinz bodies, or inclusions of denatured hemoglobin, can be found in RBC's (though they cannot be seen in routine Wright's stained peripheral blood smears, but require supravital staining). Affected persons are also more prone to infection.

Elliptocytosis

Hereditary elliptocytosis can be found in some populations residing in Melanesia. This disorder results from an RBC cytoskeletal defect that renders the shape of RBC's elongated. The stomatocytic form appears to provide resistance to malaria infection.

Persons with elliptocytosis may have a mild hemolytic anemia in infancy. Persons homozygous for this disorder may rarely have a chronic hemolytic anemia.

Duffy Negative RBC's

There are a host of antigens associated with the RBC membrane. Ordinarily, most RBC's will have the "Duffy" antigen. The presence of absence of this antigen is of no consequence, except for the fact that Duffy negative RBC's are resistant to infection with Plasmodium vivax.