Rett's syndrome

[rĕts]
n.
  1. A progressive brain disorder occurring principally in girls, characterized by autism, dementia, ataxia, and purposeless hand movements, and associated with abnormally high levels of ammonia in the blood.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.