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Many patients with 6-phosphogluconate dehydrogenase deficiency are carriers and have no symptoms. It has been discovered that symptoms manifest more frequently in female carriers. Depending on how severe the deficiency is, it has been demonstrated that enzyme activity is reduced by 35–65%. [citation needed]
If drug-induced nonautoimmune hemolytic anemia occurs secondarily to drug induced methemoglobinemia, methylene blue can be used as a first-line therapy. However methylene blue should be avoided in those with a concomitant G6PD deficiency as methylene blue may cause further oxidative hemolysis.
Methemoglobinemia can also arise in patients with pyruvate kinase deficiency due to impaired production of NADH – the essential cofactor for diaphorase I. Similarly, patients with glucose-6-phosphate dehydrogenase deficiency may have impaired production of another co-factor, NADPH. [16]
Most individuals with G6PD deficiency are asymptomatic.When it induces hemolysis, it is usually is short-lived. [5]Most people who develop symptoms are male, due to the X-linked pattern of inheritance, but female carriers can be affected due to unfavorable lyonization or skewed X-inactivation, where random inactivation of an X-chromosome in certain cells creates a population of G6PD-deficient ...
Among American ethnicities, G6PD is most prevalent among African Americans, with a prevalence of about 12.2% (males) and 4.1% (females). [27] During the Korean War , many black soldiers developed acute hemolytic anemia after primaquine for treatment or prophylaxis of malaria, which led to early understanding of this kind of anemia.
Pyruvate kinase deficiency is the second most common cause of enzyme-deficient hemolytic anemia, following G6PD deficiency. [13] The symptoms of pyruvate kinase deficiency are mild to severe hemolytic Anemia, cholecystolithiasis, tachycardia, hemochromatosis, icteric sclera, splenomegaly, leg ulcers, jaundice, fatigue, and shortness of breath. [14]
For example, a methemoglobin concentration of 1.5 g/dL may represent a percentage of 10% in an otherwise healthy patient with a baseline hemoglobin of 15 mg/dL, whereas the presence of the same concentration of 1.5 g/dL of methemoglobin in an anemic patient with a baseline hemoglobin of 8 g/dL would represent a percentage of 18.75%.
In human blood a trace amount of methemoglobin is normally produced spontaneously; the enzyme methemoglobin reductase is responsible for converting methemoglobin back to hemoglobin. [23] [24] Methemoglobinemia can be hereditary but more commonly occurs as a side effect of certain medications or by abuse of recreational drugs. [25]