Haematology · Peripheral blood smear

Sickle Cells on Peripheral Smear

Elongated, crescent-shaped red cells with target cells and polychromasia — the blood film of sickle cell anaemia (HbSS).

Peripheral blood smear with many elongated crescent-shaped red cells among round red cells
Sickle cells, polychromasia and target cells in sickle cell anaemia.Image: SpicyMilkBoy, via Wikimedia Commons — CC BY-SA 4.0.

Written & reviewed by: Kinase Medical Team · Last reviewed: 30 September 2026 · Editorial policy

Key features

  • Elongated, crescent-shaped irreversibly sickled cells are visible on a routine smear in homozygous disease.
  • Target cells and nucleated red cells may accompany them; polychromasia is also seen in this image.
  • Howell-Jolly bodies appear after autosplenectomy.
  • Red cell lifespan is only about 20 days; haemolysis severity correlates with the fraction of irreversibly sickled cells.
  • Diagnosis is confirmed by haemoglobin electrophoresis showing HbS.

Differential diagnosis

Differential diagnosis of Sickle Cells on Peripheral Smear
ConditionHow to tell it apart
Sickle cell trait (HbAS)Usually no anaemia and no sickle cells on the smear; sickling occurs only under marked hypoxia (e.g. renal medulla or in vitro).

How it appears in NEET PG

Peripheral smear images are a staple of pathology questions; sickle cells are asked directly or paired with complications such as autosplenectomy and encapsulated-organism infections.

Frequently asked questions

What are irreversibly sickled cells?

Red cells that remain sickled because their membranes have been damaged by repeated sickling. They are the crescent-shaped cells seen on a routine smear in homozygous disease, and the more of them, the more severe the haemolysis.

Why are Howell-Jolly bodies seen in sickle cell anaemia?

Repeated splenic infarction leads to autosplenectomy; without a functioning spleen, nuclear remnants in red cells are no longer removed.

How is sickle cell disease confirmed?

By haemoglobin electrophoresis (or equivalent methods) demonstrating HbS.

Sources

  1. CDC — What is sickle cell disease?
  2. Robbins Basic Pathology (textbook)
  3. Harrison's Principles of Internal Medicine (textbook)
  4. Pathoma — Fundamentals of Pathology (review text)

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For exam preparation and medical education only — not a substitute for clinical judgement, diagnosis or treatment of any patient.