Definition of Gareis-Mason syndrome

Gareis-Mason syndrome: An inherited (genetic) syndrome with characteristic features including (1) neurologically: mental retardation and aphasia (lack of speech); (2) limbs: adducted (clasped) thumbs, absent extensor pollicis longus and/or brevis muscles to the thumb, shuffling gait, and leg spasticity; (3) growth: small body size; (4) skeleton: lumbar lordosis (sway back). The syndrome is inherited as an X-linked trait and so affects mainly boys. Alternative names include MASA syndrome (MASA stands for mental retardation, aphasia, shuffling gait, and adducted thumbs), clasped thumb and mental retardation, congenital clasped thumb with mental retardation, and adducted thumb with mental retardation.