Prevalence study of Rett syndrome in North Dakota children.

Service providers for children in the state of North Dakota were surveyed to determine the prevalence rate of Rett syndrome (RS). Five patients with definite RS were identified in a population of 203,801 children (98,932 girls) 0-18 years of age yielding a prevalence rate of RS of 1 in 40,760 in North Dakota children. For girls the rate of RS is 1 in 19,786. Similar surveys of other states using comparable modes of ascertainment will be important as points of comparison for prevalence rates of RS.