DESCRIPTION

Hemolysis is the premature destruction of red blood cells (RBCs), leading to a shortened cell survival time. This destruction can occur acutely or continue chronically, depending on the etiology of the condition. The premature destruction can be caused by intrinsic factors (e.g., enzymopathies, hemoglobinopathies) or extrinsic factors (e.g., immune-mediated destruction). The breakdown of RBCs can occur either intravascularly or extravascularly (in the spleen or liver).

ETIOLOGY

• Extrinsic or acquired disorders:
  • Infectious (e.g., malaria)
  • Treatment-induced (e.g., sulfa drugs, acute/chronic hemolytic transfusion reactions, hypotonic IV fluids)
  • Immune-mediated (e.g., autoimmune hemolytic anemia [AIHA])
  • Microangiopathic (e.g., thrombotic thrombocytopenic purpura [TTP])
• Intrinsic or hereditary disorders:
  • Hemoglobinopathies (e.g., sickle cell disease [SCD])
  • RBC membrane and enzyme defects (e.g., glucose-6-phosphate dehydrogenase [G6PD] deficiency, hereditary spherocytosis [HS])

RISK FACTORS

• Acquired: ABO and/or Rh incompatibility is a risk factor for hemolysis in the newborn period.
• Hereditary: See “Genetics” below.

GENERAL PREVENTION

• Newborn screening can help identify and allow proper management of some conditions.
• Most causes of hemolysis are not preventable (e.g., hereditary cases or antibody incompatibility), although there are some that can be managed with behavioral changes:
  • Patients with G6PD deficiency should be counseled to avoid triggers (e.g., fava beans, sulfa drugs, mothballs).
  • Patients with cold-agglutinin AIHA should avoid cold temperatures.

PATHOPHYSIOLOGY

• 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 reticuloendothelial system.