The problem of dystonia and parkinsonism in girls and women with Rett syndrome (RTT). Beginning at 5-10 years of age, most RTT girls gradually develop increasing stiffness or rigidity in the muscles of the arms, legs and face, often accompanied by twisted postures of the hands and feet (dystonia). As time goes by, the dystonia gradually transforms into a condition very like Parkinson’s disease (although the cause is obviously not the same as for the well-known disease of seniors).