Diagnostic and Management of Rett Syndrome

Genetic Testing

The American College of Medical Genetics recommends sequencing of the MECP2 gene as the first step in genetic testing for Rett syndrome, as it detects point mutations responsible for 95% of classic cases 1
The American Academy of Pediatrics suggests that deletion/duplication analysis should be systematically included if sequencing is negative, as large deletions represent a significant proportion of mutations missed by standard sequencing 1, 2
The National Society of Genetic Counselors recommends peripheral blood sampling as the sample of choice for germline analysis 2

A pathogenic or likely pathogenic variant confirming the clinical diagnosis justifies family genetic counseling and evaluation of at-risk female relatives 3, 1
A variant of uncertain significance (VUS) requires family segregation analysis, a review of updated literature, and potentially functional studies in a research context 1, 4
A negative test result does not completely exclude the diagnosis if the clinical presentation is strongly suggestive; consider sequencing of alternative genes (CDKL5, FOXG1) for atypical phenotypes 1

The American College of Medical Genetics recommends in-depth discussion (traditional genetic counseling) before testing, including implications of a positive result for the patient and her family, test limitations, and the risk of incidental findings 4, 5
Informed consent must explicitly cover the risks, benefits, limitations of the test, and implications for family members 5
A minimum three-generation family history evaluation is necessary to identify other potential cases and guide result interpretation 3

Diagnostic confirmation allows avoidance of unnecessary and costly additional investigations 1
Test results guide management with appropriate surveillance of complications (epilepsy, scoliosis, respiratory and gastrointestinal disorders) 1
Accurate family genetic counseling regarding recurrence risk (low for de novo mutations but possible parental germline mosaicism in 1% of cases) 3
Access to clinical trials and emerging therapies specifically targeting MECP2 mutations 1