McLeod syndrome (/məˈklaʊd/ mə-KLOWD) is an X-linked recessive genetic disorder that may affect the blood, brain, peripheral nerves, muscle, and heart.

Other features include limb chorea, facial tics, other oral movements (lip and tongue biting), seizures, a late-onset dementia, and behavioral changes.

Blood chemistry testing may show increased lactate dehydrogenase (LDH) indicative of hemolytic anemia or elevated creatine kinase when the patient is affected by myopathy (skeletal muscle damage).

McLeod females have only occasional acanthocytes and very mild hemolysis; the lesser severity is thought to be due to X chromosome inactivation via the Lyon effect.

McLeod's red blood cells demonstrated a peculiar appearance when viewed microscopically (acanthocytic (spiky)) and showed weak expression of Kell system antigens.

[10] A pattern of pregnancy loss and infant deaths associated with the wives of King Henry VIII of England suggests he may have had McLeod syndrome given his eventual premature mental deterioration.