Rett syndrome in Northern Tuscany (Italy): family tree studies

Four cases of Rett syndrome were ascertained among 19 060 girls born between 1978 and 1990 in a small, defined area of Northern Tuscany (Italy) (prevalence rate of 2.1 per 10 000). A fifth girl with a reported clinical picture of Rett syndrome, born in 1978 and deceased at age 13, was also found. One of the four Rett syndrome cases had a healthy female dizygote twin. Family tree studies going back as far as the 17th century were performed. A number of common ancestors were found in different generations leading to a single family tree encompassing all four Rett syndrome cases. In addition, a Rett girl with preserved speech, born in 1974. was found as part of this family tree. These observations confirm the role of genetic factors in the etiology of Rett syndrome and support the hypothesis that Rett syndrome is a clinically variable phenotype.