Anemia, Sickle Cell

Anemia, Sickle Cell is a topic covered in the 5-Minute Clinical Consult.

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Basics

Description

  • Hereditary, hemoglobinopathy marked by chronic hemolytic anemia, acute episodes of painful “crises,” and increased susceptibility to infections
  • The heterozygous condition (Hb AS), sickle cell trait, is usually asymptomatic without anemia.
  • Synonym(s): sickle cell disease (SCD); Hb SS disease
Pediatric Considerations
  • Sequestration crises and hand–foot syndrome seen typically in infants/young children
  • Strokes occur mainly in childhood.
  • Adolescence/young adulthood
    • Frequency of complications and organ/tissue damage increases with age.
    • Psychological complications: body image, interrupted schooling, restriction of activities; stigma of disease; low self-esteem
Pregnancy Considerations
  • Complicated, especially during 3rd trimester and delivery
    • Fetal mortality 35–40%. Fetal survival is >90% if the fetus reaches the 3rd trimester.
    • High prevalence of small for gestational age (SGA) babies
  • Increased risk of thrombosis, preterm delivery, pain, toxemia, infection, pulmonary infarction, and phlebitis
  • Partial exchange transfusion in 3rd trimester may reduce maternal morbidity and fetal mortality but is controversial.
  • Chronic transfusions have been effective in diminishing pain episodes in pregnant women. However, this method should be used with caution due to risk of alloimmunization.

Epidemiology

Prevalence
  • ~90,000 Americans have sickle cell anemia (SCA), and 3.5 million people in the United States have sickle cell trait.
  • The condition affects mainly people of African descent. Hispanic, Middle-eastern, and Asian Indian ancestry may also be affected.

Etiology and Pathophysiology

  • Hemoglobin S results from the substitution of the amino acid valine for glutamic acid at the sixth position of the β-globin chain.
  • HbS polymerizes in the RBC in the deoxygenated state resulting in RBC sickling.
  • Sickle RBCs are inflexible, causes increased blood viscosity, stasis, obstruction of small arterioles and capillaries, and ischemia.
  • Chronic anemia; crises
    • Vaso-occlusive crisis: tissue ischemia and necrosis; progressive organ failure/tissue damage from repeated episodes
    • Hand–foot syndrome: Vessel occlusion/ischemia affects small blood vessels in hands or feet.
    • Aplastic crisis: suppression of RBC production by severe infection (e.g., parvoviral and other viral infections)
    • Suppression of RBC production
    • Hyperhemolytic crisis: accelerated hemolysis with reticulocytosis; increased RBC fragility/shortened lifespan
    • Sequestration crisis: splenic sequestration of blood (only in young children as spleen is later lost to autoinfarction)
  • Susceptibility to infection: impaired/absent splenic function leading to decreased ability to clear infection; defect in alternate pathway of complement activation
  • Increased RBC destruction causes decreased hemoglobin levels and results in anemia and fatigue.
  • Sickle cells exhibit increased adhesion and decreased ability to maneuver through small vessels, leading to vaso-occlusion.

Genetics
  • Autosomal recessive. Homozygous condition, Hb SS; heterozygous condition, Hb AS
  • The heterozygote condition can also be combined with other hemoglobinopathies: Sickle cell hemoglobin C (HbSC) disease and Sβ+ thalassemia are clinically similar to the heterozygous condition, whereas Sβ thalassemia is clinically similar to the homozygous condition.

Risk Factors

  • Vaso-occlusive crisis (“painful crisis”): hypoxia, dehydration, fever, infection, acidosis, cold, anesthesia, strenuous physical exercise, smoking
  • Aplastic crisis (suppression of RBC production): severe infections, human parvovirus B19 infection, folic acid deficiency
  • Hyperhemolytic crisis (accelerated hemolysis with reticulocytosis): acute bacterial infections, exposure to oxidant

General Prevention

  • Prevention of crises
    • Avoid hypoxia, dehydration, cold, infection, fever, acidosis, and anesthesia.
    • Prompt management of fever, infections, pain
    • Hydration
    • Avoid alcohol and smoking.
    • Avoid high-altitude areas.
  • Minimizing trauma: Aseptic technique is imperative.

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Citation

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TY - ELEC T1 - Anemia, Sickle Cell ID - 116027 Y1 - 2019 PB - 5-Minute Clinical Consult, Updating UR - https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116027/all/Anemia__Sickle_Cell ER -