Bone mass in Rett syndrome: association with clinical parameters and MECP2 mutations.

Rett syndrome (RTT) is an X-linked neurodevelopmental disorder caused by mutations in the MECP2 gene. In 49 female RTT children, aged 1.9-17 y, bone mass was assessed and correlated with clinical parameters and mutations involving the MECP2 gene. We also studied five adult females, aged 20-33 y, and one male child, aged 6 y. Lumbar spine bone mineral content (BMC) and bone mineral density (BMD) were correlated with weight, height, BMI, clinical severity, degree of scoliosis, use of anticonvulsants, and ambulatory status. L1-L4 BMD and BMC showed that 48.9% of them had BMD values >2 SD below age-related norms. BMD values were in the osteoporotic range in the five adult females with RTT. Eleven percent of the children and adults with RTT experienced fractures. Low bone mass was correlated with marginal significance to clinical severity and ambulation but not to scoliosis or anticonvulsant use. Lowest bone mass occurred in patients with T158M or R270X mutations but without statistical significance. Studies in a murine model of RTT confirmed low bone mass as an inherent component of this syndrome. MECP2 mutations and clinical parameters impact bone mass in RTT, but an association with a specific mutation was not demonstrable.