acanthocytes

Acanthocytes, also called spur cells, are abnormal red blood cells characterized by irregular, variably sized spicules projecting from the cell membrane, giving a star-like or crenated appearance. They differ from echinocytes (burr cells), which have uniform, evenly spaced projections; acanthocytes have irregular projections and variable spacing.

The shape reflects changes in red cell membrane composition and stability. Acanthocytosis is associated with an increased cholesterol-to-phospholipid ratio in the membrane and altered surface charge, which reduces deformability and promotes membrane instability. Causes include liver disease (especially cirrhosis and alcoholic liver disease), and lipid metabolism disorders such as abetalipoproteinemia. It is also a feature of neuroacanthocytosis syndromes, including chorea-acanthocytosis (VPS13A mutations) and McLeod syndrome (XK gene), where acanthocytes may accompany neurological manifestations.

Clinical significance varies: acanthocytes are most often identified on a peripheral blood smear and serve as a diagnostic clue rather than a specific diagnosis. Their presence can direct evaluation toward hepatic dysfunction, lipid disorders, or neurodegenerative or neuroacanthocytic conditions. In the setting of liver disease with hemolysis, the phenomenon may contribute to spur cell anemia, a form of hemolytic anemia linked to severe membrane abnormalities.

Diagnosis is established by examination of the peripheral smear, with morphology guiding further etiologic testing and management focused on the underlying condition. Treatments are not specific to acanthocytosis itself but address the associated disease.