Clinical, neurophysiological and immunological correlations in classical Rett syndrome.

Rett syndrome (RTT) is neurodevelopmental disorder with the onset at critical period of postnatal ontogenesis and age dependent occurrence of clinical manifestations. The aim of the present study was to investigate possible correlations of the age of disease onset with clinical manifestations at the stage 3 of illness and neurobiological parameters. The study was carried out in 38 girls with classical RTT, aged from 3 to 7 years, and twenty and eighteen patients with the disease onset before and after the age of one year were divided into the groups 1 and 2 (Gr1 and Gr2), respectively. Quantitative EEG (QEEG) and measurement of the serum levels of autoantibodies (AAB) to nerve growth factor (NGF) were performed. Clinically, speech and motor functions were significantly more severely affected in the Gr1 than in the Gr2. In QEEG, spectral density of theta activity was significantly higher in Gr1 than in the Gr2. The titer of AAB to NGF was significantly increased in comparison with healthy controls, and the titer in Gr2 was higher than in Gr1. The data obtained suggests that patients with the classical RTT can be divided into subgroups according to the age of disease onset and genetic factors such as mosaicism of MeCP2 mutation may be associated with the heterogeneity of phenotype in RTT patients.