Educational Content: This article is for informational purposes only and does not constitute medical advice. Always consult a healthcare provider for diagnosis and treatment.
Definition of MASA syndrome
Medically reviewed by Dr. Otari Nergadze, Neurosurgeon | Updated: January 2026
MASA syndrome: MASA stands for mental retardation, aphasia, shuffling gait, and adducted thumbs. Features of the syndrome include:
- neurologically: mental retardation and aphasia (lack of speech);
- limbs: adducted (clasped) thumbs, absent extensor pollicis longus and/or brevis muscles to the thumb, shuffling gait, and leg spasticity;
- growth: small body size;
- skeleton: lumbar lordosis (sway back).
MASA is inherited as an X-linked trait and so affects mainly boys. Alternative names for MASA include clasped thumb and mental retardation, congenital clasped thumb with mental retardation, adducted thumb with mental retardation, and the Gareis- Mason syndrome.