MECP2 Variants in Males: More Common than Previously Appreciated

To assess the age and MECP2 variants of recently identified males and set the stage for further study of clinical features in males.

Genetic information on the specific MECP2 variant was acquired from the coordinator (K.F.) of the Parent Group for Males. Data were collected indicating whether these variants were de novo or transmitted from the mother and whether males who appeared to meet the diagnostic criteria for Rett syndrome had mosaicism for the MECP2 variant.

Fifty-nine males were identified through the parent group. Their ages ranged from 2 to 28 years, with the median age being 7.0 years and the mean age being 10.8 years. Of these variants, 46 (78.0%) were de novo, nine (15.3%) were maternally inherited, and for four (6.8%) inheritance was not known. Eleven (18.6%) were mosaic, 10 with somatic mosaicism and one with Klinefelter syndrome (47XXY). Together with males reported previously from the US Natural History Study, the total group represents 85 males, of whom 27 are deceased.

These data on males with MECP2 variants are important to caregivers, physicians, and researchers to begin to characterize their historical and clinical features, improve diagnostic recognition and overall care, and accelerate access to therapeutic studies including gene replacement strategies. Equal access to such therapies for males is critical.