Chapter 101. Hemolytic Anemias and Anemia Due to Acute Blood Loss (Part 12)

Figure 101-6Peripheral blood smear from a 5-year-old G6PD-deficient boy with acute favism.A very small minority of subjects with G6PD deficiency have CNSHA of variable severity. The patient is always a male, usually with a history of NNJ, who may present with anemia or unexplained jaundice, or because of gallstones later in life. The spleen may be enlarged. The severity of anemia ranges from borderline to transfusion-dependent. The anemia is usually normo-macrocytic, withreticulocytosis. Bilirubin and LDH are increased. Although hemolysis is, by definition, chronic in these patients, they are also vulnerable to acute oxidative damage, and therefore the same agents...
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Chapter 101. Hemolytic Anemias and Anemia Due to Acute Blood Loss (Part 12) Chapter 101. Hemolytic Anemias and Anemia Due to Acute Blood Loss (Part 12)Figure 101-6 Peripheral blood smear from a 5-year-old G6PD-deficient boy with acutefavism. A very small minority of subjects with G6PD deficiency have CNSHA ofvariable severity. The patient is always a male, usually with a history of NNJ, whomay present with anemia or unexplained jaundice, or because of gallstones later inlife. The spleen may be enlarged. The severity of anemia ranges from borderline totransfusion-dependent. The anemia is usually normo-macrocytic, withreticulocytosis. Bilirubin and LDH are increased. Although hemolysis is, bydefinition, chronic in these patients, they are also vulnerable to acute oxidativedamage, and therefore the same agents (see Table 101-5) that can cause acute HAin people with the ordinary type of G6PD deficiency will cause severeexacerbations in people with the severe form of G6PD deficiency. In some casesof CNSHA, the deficiency of G6PD is so severe in granulocytes that it becomesrate-limiting for their oxidative burst, with consequent increased susceptibility tobacterial infections. Laboratory Diagnosis The suspicion of G6PD deficiency can be confirmed by semiquantitativemethods often referred to as screening tests, which are suitable for populationstudies and can correctly classify male subjects, in the steady state, as G6PD-normal or G6PD-deficient. However, in clinical practice a diagnostic test isusually needed when the patient has had a hemolytic attack: this implies that theoldest, most G6PD-deficient red cells have been selectively destroyed, and youngred cells, having higher G6PD activity, are being released into the circulation.Under these conditions, only a quantitative test can give a definitive result. Inmales this test will identify normal hemizygotes and G6PD-deficient hemizygotes;among females some heterozygotes will be missed, but those who are at most riskof hemolysis will be identified. G6PD Deficiency: Treatment The acute HA of G6PD deficiency is largely preventable by avoidingexposure to triggering factors of previously screened subjects. Of course, thepracticability and cost-effectiveness of screening depends on the prevalence ofG6PD deficiency in each individual community. Favism is entirely preventable bynot eating fava beans. Prevention of drug-induced hemolysis is possible in mostcases by choosing alternative drugs. When acute HA develops and once its causeis recognized, no specific treatment is needed in most cases. However, if theanemia is severe, it may be a medical emergency, especially in children, requiringimmediate action, including blood transfusion. If acute renal failure develops,hemodialysis may be necessary, but if there is no previous kidney disease, fullrecovery is the rule. The management of NNJ associated with G6PD deficiency isno different from that of NNJ due to other causes. In cases with CNSHA, if the anemia is not severe, regular folic acidsupplements and regular hematologic surveillance will suffice. It will be importantto avoid exposure to potentially hemolytic drugs, and blood transfusion may beindicated when exacerbations occur, mostly in concomitance with intercurrentinfection. In rare patients, regular blood transfusions may be required; appropriateiron chelation should be instituted in such cases. Unlike in hereditaryspherocytosis, there is no evidence of selective red cell destruction in the spleen:however, in practice splenectomy has proven beneficial in severe cases. Other Abnormalities of the Redox System As mentioned above, GSH is a key player in the defense against oxidativestress (Fig. 101-4). Inherited defects of GSH metabolism are exceedingly rare, buteach one of them can give rise to chronic HA (Table 101-4). A rare, peculiar,usually self-limited severe HA of the first month of life, called infantilepoikilocytosis, may be associated with deficiency of glutathione peroxidase(GSHPx) due not to an inherited abnormality but to transient nutritional deficiencyof selenium, an element essential for the activity of GSHPx.