GLUCOSE-6-PHOSPHATE DEHYDROGENASE DEFICIENCY
The abnormality in this disorder is in the G-6-PD gene; this gene produces an enzyme within the RBC that is essential for mem-brane stability. A few patients have inherited an enzyme so defec-tive that they have a chronic hemolytic anemia; however, the most common type of defect results in hemolysis only when the RBCs are stressed by certain situations, such as fever or the use of certain medications. The disorder came to the attention of researchers during World War II, when some soldiers developed hemolysis while taking primaquine, an antimalarial agent. African Ameri-cans and people of Greek or Italian origin are those primarily af-fected by this disorder. The type of deficiency found in the Mediterranean population is more severe than that in the African Caribbean population, resulting in greater hemolysis and some-times in life-threatening anemia. All types of G-6-PD deficiency are inherited as X-linked defects; therefore, many more men are at risk than women. In the United States, about 12% of African American males are affected. The deficiency is also common in those of Asian ancestry and in certain Jewish populations.
Medications that have hemolytic effects for people with G-6-PD deficiency are oxidant drugs. These medications include antimalarial agents (eg, chloroquine [Aralen]), sulfonamides (eg, trimethoprim and sulfamethoxazole [Septra]), nitrofurantoin (eg, Macrodantin), common coal tar analgesics (including aspirin in high doses), thiazide diuretics (eg, hydrochlorothiazide [Hydro-DIURIL], chlorothiazide [Diuril]), oral hypoglycemic agents (eg, glyburide [Micronase], metformin [Glucophage]), chloram-phenicol (Chloromycetin), and vitamin K (phytonadione [Aqua-Mephyton]). In affected people, a severe hemolytic episode can result from ingestion of fava beans.
Patients are asymptomatic and have normal hemoglobin levels and reticulocyte counts most of the time. However, several days after exposure to an offending medication, they may develop pal-lor, jaundice, and hemoglobinuria (hemoglobin in the urine). The reticulocyte count rises, and symptoms of hemolysis develop. Spe-cial stains of the peripheral blood may then disclose Heinz bodies (degraded hemoglobin) within the RBCs. Hemolysis is often mild and self-limited. However, in the more severe Mediterranean type of G-6-PD deficiency, spontaneous recovery may not occur and transfusions may be necessary.
The diagnosis is made by a screening test or by a quantitative assay of G-6-PD.
The treatment is to stop the offending medication. Transfusion is necessary only in the severe hemolytic state, which is more com-monly seen in the Mediterranean variety of G-6-PD deficiency.
The patient should be educated about the disease and given a list of medications to avoid. If hemolysis does develop, nursing inter-ventions are the same as for hemolysis from other causes.