Hematology

Sickle Cell Disease

Autosomal recessive haemoglobinopathy from HbS (beta-globin Glu6Val) that polymerises on deoxygenation, causing vaso-occlusion, haemolysis and end-organ damage.

Last reviewed 30 Jun 2026 - MedicoMedics editorial team

Pathophysiology

HbSS or compound heterozygotes; deoxy-HbS polymers deform erythrocytes, causing microvascular occlusion, chronic haemolysis and nitric oxide depletion.

Sources: NHLBI Sickle Cell 2020; Exa-cel (NEJM 2024;390:1649)

Presentation

Vaso-occlusive pain crises, dactylitis in infants, acute chest syndrome, stroke, splenic sequestration and functional asplenia (encapsulated organism risk), priapism, avascular necrosis, chronic pain.

Diagnosis

Newborn screening (Hb electrophoresis or HPLC); confirms HbS. Peripheral smear: sickle cells, Howell-Jolly bodies, target cells.

Management

Hydroxyurea (increases HbF), voxelotor (Hb polymerisation inhibitor), crizanlizumab (P-selectin), l-glutamine; transfusion for stroke/ACS; chronic transfusion + hydroxyurea for stroke prevention; allogeneic HSCT curative; gene therapies (exa-cel, lovo-cel) approved.

Sample USMLE-style MCQs

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Question 1

A 6-month-old has painful hand-foot swelling and Hb 8. Peripheral smear: sickle cells. Best long-term therapy?

Question 2

A patient with SCD develops hypoxia, chest pain and new infiltrate. Diagnosis?

Question 3

Which vaccine is critical due to functional asplenia?

Question 4

Which drug reduces vaso-occlusive crisis by blocking P-selectin?

Question 5

Which gene therapy uses CRISPR to reactivate HbF?

References

Primary guidelines and peer-reviewed sources used for this entry. Reviewed 30 Jun 2026 by MedicoMedics editorial team.

Frequently asked

Prophylaxis in children?

Penicillin V until age 5 + pneumococcal/meningococcal/Hib vaccines.

Acute chest syndrome trigger?

Fat embolism, infection, hypoventilation.

Which new curative therapy?

Exagamglogene autotemcel (CRISPR gene editing).

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