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Hemolytic anemia is defined as the destruction of red blood cells (RBCs) before their normal 120-day life span. It includes many separate and diverse entities whose common clinical features can aid in the identification of hemolysis. Hemolytic anemia exists on a spectrum from chronic to life-threatening, and warrants consideration in all patients with unexplained normocytic or macrocytic anemia.
SORT: KEY RECOMMENDATIONS FOR PRACTICE
| Clinical recommendation | Evidence rating | References |
|---|---|---|
| After hemolytic anemia is confirmed, a peripheral blood smear should be ordered to determine the etiology. | C | 1 |
| Glucocorticoids are the first-line treatment of warm autoimmune hemolytic anemia. | C | 4 |
| The PLASMIC score can be used to assess the likelihood of thrombotic thrombocytopenic purpura when ADAMTS13 cannot be easily measured. | C | 10 |
| Do not give antibiotics to children with Escherichia coli diarrhea because antibiotics increase the risk of hemolytic uremic syndrome. | B | 15 |
| G6PD activity should be measured in infants with jaundice and a family history or geographic background suggestive of possible deficiency. | C | 28 |
G6PD = glucose-6-phosphate dehydrogenase.
A = consistent, good-quality patient-oriented evidence; B = inconsistent or limited-quality patient-oriented evidence; C = consensus, disease-oriented evidence, usual practice, expert opinion, or case series. For information about the SORT evidence rating system, go to https://www.aafp.org/afpsort.
Pathophysiology
Premature destruction of RBCs can occur intravascularly or extravascularly in the reticuloendothelial system, although the latter is more common. The primary extravascular mechanism is sequestration and phagocytosis due to poor RBC deformability (i.e., the inability to change shape enough to pass through the spleen). Antibody-mediated hemolysis results in phagocytosis or complement-mediated destruction, and can occur intravascularly or extravascularly. The intravascular mechanisms include direct cellular destruction, fragmentation, and oxidation. Direct cellular destruction is caused by toxins, trauma, or lysis. Fragmentation hemolysis occurs when extrinsic factors produce shearing and rupture of RBCs. Oxidative hemolysis occurs when the protective mechanisms of the cells are overwhelmed.1
The etiologies of hemolysis are numerous (Table 1). The hemoglobinopathies lead to splenic destruction and, in the case of sickle cell disease, likely multiple mechanisms of destruction. Inherited protein deficits lead to increased destruction in membranopathies. Enzymopathies result in hemolysis due to overwhelming oxidative stress or decreased energy production. In immune-mediated hemolytic anemia, antibodies bind with the RBCs, resulting in phagocytosis or complement-mediated destruction. The extrinsic nonimmune...