Additional clinical and cytogenetic findings associated with Rett syndrome.

An analysis of all aphidicolin-inducible breakpoints has been carried out in PHA stimulated T-lymphocytes of five patients with classical Rett syndrome, their mothers and a group of age matched controls. Observed breakpoints were divided into two groups: common, rare, and those recorded by others but not assigned as fragile sites by CCM92 and a group of non-specified breakpoints recurrently found in our ongoing study of fragile sites. In addition cooccurrence of trisomy X in one patient and de novo pericentromeric inversion on chromosome 2 in another Rett syndrome patient are reported. The co-occurrence with the Tourette syndrome in two of our families, and the fact that both Rett and Tourette syndrome are associated with movement disorders, possible dopaminergic hypersensitivity and increased chromosomal fragility in subsets of fragile sites, may suggest a possible avenue for further research. The cytogenetic findings indicate that both X-linked and autosomal regulatory region(s) may be part of a complex genetic alteration in association with Rett syndrome.