Males with pathogenic MECP2 mutations usually die during infancy stage from severe encephalopathy, unless they have an extra X chromosome (often described as Klinefelter's syndrome), or have somatic mosaicism.
Females can live up to 40 years or more. Abnormal lab data values on Rett disorder may show:
* EEG abnormalities from 2 years of age
* atypical glycolipids
* elevated levels of beta-endorphins and glutamate
* reduction of substance P
* decreased levels of nerve growth factors
Mortality rate among children with Rett disorder is approximately at 1.2% per year.
High proportion of deaths are abrupt; due to:
* heart conduction problem - abnormally prolonged QT interval on ECG
* spontaneous brainstem dysfunction
* respiratory arres