Sickle cell disease

Background

• Genetic mutation of the hemoglobin beta chain, most commonly an E6V substitution, causing the formation of hemoglobin S
• Most common in people with African ancestry, though also occurs in Hispanic, southern European, Middle Eastern, and Indian people
• Life expectancy is 20-30 years shorter

Clinical Manifestations

• Chronic anemia

Crises

• Four major sickle crises:
  • Vasoocclusive pain crisis
  • Hemolytic crisis
  • Aplastic crisis (often associated with parvovirus)
  • Splenic sequestration crisis

Diagnosis

• Hemoglobin quantification can help to identify the type of sickle cell disease
  • HbS is sickle hemoglobin
  • HbA is normal adult hemoglobin and HbA₂ is the minor variant of adult hemoglobin
  • HbF is fetal hemoglobin
  • HbC is a hemoglobin variant that causes sickle cell disease when paired with HbS

Genotype	Hb (g/L)	HbS (%)	HbA (%)	HbA2 (%)	HbF (%)	HbC (%)
AS (trait)	normal	≤40	>60	<3.5	≤1
SS	60-90	>90		<3.5	<10
Sβ0-thalassemia	70-90	>80		>3.5	<20
Sβ+-thalassemia	90-120	>60	10-30	>3.5	<20
SC	90-140	50		<3.5	≤1	45