Premature destruction of RBCs, either intravascularly or extravascularly, leading to a shortened red cell survival time. The premature destruction can be caused by intrinsic factors (defects within the RBC itself) or extrinsic factors (factors outside the RBC leads to premature destruction).
- Acquired (extrinsic): ABO and/or Rh incapability is a risk factor in the newborn period.
- Hereditary (intrinsic): Although many hereditary disorders are autosomal dominant, 20% of these patients represent new spontaneous mutations and have no affected family members.
- Hemoglobinopathies are generally autosomal recessive or the result of compound heterozygosity.
- RBC membrane defects and enzyme defects may be autosomal dominant, recessive, or X-linked.
- Acquired (extrinsic): Most causes of acquired, non–transfusion-related hemolytic disease are not preventable.
- Hereditary (intrinsic): Although there is no way to prevent hereditary forms of hemolysis, newborn screening can help identify and allow proper management of some conditions. Patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency should be counseled to avoid triggers such as fava beans, broad beans, and mothballs.
- Intravascular hemolysis occurs within the circulation as a direct result of trauma, complement fixation, and cellular destruction.
- Extravascular hemolysis generally occurs in the spleen (or liver) as misshaped and/or older red cells are recognized and destroyed by the RE system.
- Extrinsic or acquired disorders
- Immune mediated
- Intrinsic or hereditary disorders
- RBC membrane and enzyme defects
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