New experience with Rett syndrome in France: the problem of atypical cases.

Thirty-five patients with typical Rett syndrome have been observed by the authors. Fourteen patients with behavioral features suggestive of RS but who lacked some of the diagnostic criteria are reported. They were divided into 3 groups: 1) abnormal development from birth, 2) acute post-epileptic onset, and 3) encephalopathy with a known etiology different from RS. These 14 patients included 3 boys. In none of these cases was there an obvious history of acquired, progressive deterioration. The latter is essential for the diagnosis of RS.