Skewed X chromosome inactivation in carriers is not a constant finding in FG syndrome.

Genetic heterogeneity has been demonstrated in FG syndrome. We report a systematic study of the X-inactivation profile of obligate carriers and other females in FG pedigrees. It was expected that the characterization of particular X-inactivation profiles in carriers in some families might be related to the same mutated gene. Analysis of the X-inactivation profiles in carriers demonstrated different profiles but no correlation was found with the results of the linkage study.