Hemolysis

Basics

DESCRIPTION

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).

RISK-FACTORS

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.

GENETICS

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.

GENERAL-PREVENTION

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.

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 RE system.

ETIOLOGY

Extrinsic or acquired disorders
- Infectious
- Drug-induced
- Immune mediated
- Microangiopathic
Intrinsic or hereditary disorders
- Hemoglobinopathies
- RBC membrane and enzyme defects

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