Rett syndrome in adolescent and adult females: Clinical and molecular genetic findings

Rett syndrome (RTT) is a neurodevelopmental disorder which is diagnosed clinically. We report on 30 adolescent and adult females with classical or atypical RTT of whom 24 have a MECP2 mutation. In these 24 females, the clinical manifestations, degree of severity, and disorder profiles are discussed as well as the genotype phenotype correlation. After X-chromosome inactivation (XCI) study in these cases, we found no correlation between skewing and milder phenotype. Three large deletions were found after additional Southern blot analysis in three classical RTT cases. We confirm that early truncating mutations in MECP2 are responsible for a more severe course of the disorder. Three disorder profiles related to the missense mutations R133C and R306C, and to deletions in the C terminal segment are described and are of interest for further clinical study on larger numbers of cases. The R133C genotype has a predominantly autistic presentation while the R306C genotype is associated with a slower disease progression. The phenotype of the "hotspot" deletions in the C terminal segment is predominantly characterized by rapid progressive neurogenic scoliosis. Older women with RTT are underdiagnosed: seven adults were first diagnosed as having RTT between 29 and 60 years of age, and confirmed on finding a MECP2 mutation. Knowledge of the clinical phenotype of RTT at an adult age is important for all involved in the care of these individuals. The involvement of the parent support group is very important in this matter.