Sickle Cell Anemia: Pathophysiology, Complications, and Management

Disease Mechanism

Sickle cell anemia (HbSS) is an autosomal recessive disorder caused by a point mutation (Glu6Val) in the β-globin gene. Deoxygenated HbS polymerizes, distorting RBCs into rigid sickle shapes.

Key Pathophysiologic Consequences

• Hemolysis: Sickle RBCs survive 10–20 days (vs. 120 days normal) → chronic anemia, reticulocytosis, jaundice, bilirubin gallstones.
• Vaso-occlusion: Rigid cells obstruct microvasculature → ischemia-reperfusion injury, inflammation, endothelial activation, pain crises.
• Endothelial dysfunction: Reduced NO bioavailability, adhesion molecule upregulation, procoagulant state.

Major Acute Complications

• Vaso-occlusive crisis (VOC): Severe bone/joint/abdominal pain; most common cause of hospitalization.
• Acute chest syndrome (ACS): New pulmonary infiltrate + fever/respiratory symptoms; leading cause of death.
• Splenic sequestration: Sudden splenic enlargement, hemodynamic instability (esp. children).
• Aplastic crisis: Parvovirus B19 → transient erythroblastopenia; severe anemia.
• Stroke: Overt (10% by age 20) or silent infarcts; due to intracranial stenosis (moyamoya).
• Priapism: Stuttering or prolonged; risk of impotence.

Chronic Organ Damage

• Renal: hyperfiltration → proteinuria → CKD
• Pulmonary: hypertension, fibrosis
• Cardiac: diastolic dysfunction, cardiomyopathy
• CNS: silent infarcts, cognitive decline
• Ocular: proliferative retinopathy
• Bone: avascular necrosis (femoral/humeral heads)
• Leg ulcers (ankle)

Disease-Modifying Therapies

• Hydroxyurea: Increases HbF, reduces VOC/ACS/transfusion need; standard of care.
• Voxelotor: HbS polymerization inhibitor; improves anemia.
• Crizanlizumab: P-selectin inhibitor; reduces VOC frequency.
• L-glutamine: Reduces oxidative stress; modest VOC reduction.
• Curative: Allogeneic HSCT (matched sibling best); gene therapy (lentiviral β-globin, CRISPR) – emerging.

Preventive Care

• Penicillin prophylaxis (children <5 yrs, post-splenectomy)
• Vaccinations: pneumococcal (PCV20/PPSV23), meningococcal, Hib, annual flu, COVID
• Transcranial Doppler (TCD) screening ages 2–16 for stroke risk
• Folic acid 1 mg/day
• Comprehensive multidisciplinary care