Epilepsy and EEG findings in patients with FMR1 gene mutation

We have analysed family history, clinical presentation, EEG findings and results of molecular analysis in 23 patients with an amplification in the FMR-1 gene. In fifteen (15/23 or 65.2%) patients EEG abnormaliteis were found. In eight patients with fragile X syndrome (8/23 or 34.8%) EEG patterns were epileptogenic. Five (5/23 or 21.7%) had documented seizures. They started between age 3 and age 8. In four instances seizures were of partial type or partial with secondary generalisation, while only one patient had primary generalised grand mal epilepsy. In three patients without epilepsy particular epileptogenic pattern in form of centrotemporal focal spikes was found. In remaining seven (7/23 or 30.4%) patients unspecific EEG abnormalities were noted. Epilepsy was recorded only in males with distinct clinical presentation and full mutation. Mosaic carriers as well as females with full mutation that can be also considered as mosaics because of the X- inactivation pattern, had milder clinical symptoms, no seizures or characteristic EEG pattern. All points to the conclusion that the development of seizures and characteristic EEG pattern in individuals with fragile X syndrome is influenced by genotype modifications such as mosaicism or metilation status, but probably also by additive effect of other genes predisposing to seizures and by stochastic factors.