Reversible autism and intellectual disability in children.

Studies on young children with reversible autism and intellectual disability are discussed. Present evidence suggests a clear cause in a minority of cases including early institutionalization, Landau and Kleffner syndrome, and other early onset epilepsies, intrauterine rubella, and blindness. The majority of cases have normal laboratory results and some have early onset Tourette syndrome. Preliminary data of a follow-up study of this last group are reported in 15 patients suggesting the possibility of two subgroups, one represented by early onset Tourette syndrome phenotype, characterized by a positive family history, and by its appearance at the same time as regression and persistence into adolescence while the other of a different nature. Genetic studies could be of help to clarify this issue and support a diagnosis of favorable outcome in young children.