Clinical research: MeCP2 duplication distinct from autism
Most boys who have an extra copy of the MeCP2 gene have a diagnosis of autism, but their symptoms differ from those of classic autism, according to a study published 20 November in Autism Research1. In particular, these boys have social deficits that are milder than those characteristic of autism.
Mutations in MeCP2 are the primary cause of Rett syndrome, a developmental disorder characterized by some autism-like symptoms such as poor communication skills and repetitive behaviors.
Boys who have an extra copy of the gene have symptoms that more closely resemble autism, including developmental delay, seizures and motor deficits. MeCP2 duplication also leads to an immune deficiency, which may explain why boys with the syndrome have frequent and severe respiratory infections.
There are few known girls with this syndrome, probably because the gene is on the X chromosome, one copy of which is inactivated throughout the body. With some exceptions, inactivation usually favors the mutant copy of the chromosome.
In the new study, researchers compared the symptoms of ten boys who have an extra copy of MeCP2 with those of nine boys who have classic autism.
Seven of the ten boys with excess MeCP2 have a diagnosis of autism with the characteristic social deficits and repetitive behaviors, according to the Autism Diagnostic and Observation Schedule. However, their social deficits are milder than those in boys with classic autism.
Nine of the ten boys with excess MeCP2 seem not to be bothered by pain or changes in temperature, according to the parental report Sensory Profile Questionnaire. Studies have described similar symptoms in children with Rett syndrome.
The researchers did not give this questionnaire to the boys with classic autism, but children with autism are often particularly sensitive to sensory sensations.
1: Peters S.U. et al. Autism Res. Epub ahead of print (2012) PubMed