Mosaicism in Males with Fragile X Syndrome

This study[1] looked at mosaicism in males with Fragile X syndrome. Most males with FXS make very little or no amount of a protein, called FMR1, that is important for brain development. This happens because the gene that makes this protein has been “turned off” in all of the cells in their body by a process called methylation. However, some males with FXS have what is called “methylation mosaicism” which means that some, though not all, of their cells have a gene that has not been turned off by methylation and can still make the FMR1 protein.

In this study, participants with methylation mosaicism tended to have less severe intellectual disability and better social and functional skills. More research needs to be done, but knowing more about how FXS differs in people with and without methylation mosaicism may eventually help guide expectations and treatment of individuals with FXS.

Read the article at American Journal of Medical Genetics Part A