Clasped-thumb mental retardation (MASA) syndrome: confirmation of linkage to Xq28.

We describe a 5-generation Hispanic family with 13 males and 1 female affected with MASA syndrome. The proposita, a 17-year-old female, and her affected male relatives shared many of the cognate manifestations--mental retardation (14/14), aphasia or delayed speech (13/13), shuffling gait (8/13), adduction of thumbs (14/14)--as well as scoliosis (2/13) and increased deep tendon reflexes in the lower extremities (10/13). Southern analysis with the polymorphic DNA probes DXS14 (Xp11), DXS72 (Xq21), and F8C (Xq28) confirmed linkage to the Xq28 region with a maximum lod score of 3.01 for this family.