Sickle Cell Disease

Basics

DESCRIPTION

Sickle cell disease (SCD) is a disease caused by a homozygous inheritance of a one base pair change leading to an amino acid change in the beta globin gene at the sixth position: glutamic acid to valine on chromosome 11. The mutation leads to undesired polymerization of hemoglobin in the red cell causing membrane distortion which has systemic effects on the host.

EPIDEMIOLOGY

  • The incidence of SCD is 1 in 500 African Americans, 1 in 36,000 Hispanics, with a lesser frequency in other ethnic groups. The incidence of sickle cell trait (SCT) in African Americans is 1 in 14.
  • There are 70,000 to 100,000 affected individuals with SCD in the United States.

RISK-FACTORS

GENETICS

  • SCD is autosomal recessive.
  • The disease can be caused by homozygous inheritance of beta globin with the S mutation or by inheriting the mutated beta globin S with an additional beta globin mutation such as abnormal beta globin causing hemoglobin C, beta thalassemia, or DLos Angeles, and OArab.

PATHOPHYSIOLOGY

  • Membrane distortion caused by this abnormal hemoglobin leads to: increased adhesion to vascular endothelium, activation of cytokines leading to activation of platelets and leukocytes, and ultimately to vaso-occlusion.
  • Extravascular hemolysis causes release of free hemoglobin and subsequent oxidative stress causing vasoconstriction, inflammation and platelet activation.

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