Article Title
Robertson L, Hall S, Jacoby P, Ellaway C, De Klerk N, Leonard H. The association between behaviour and genotype in Rett Syndrome using the Australian Rett Syndrome Database. American Journal of Medical Genetics- Part B Neuropsychiatrics. 2006;141(2):177-83. Download snapshot, see article abstract.
Background
Common behaviours which occur in girls and women with Rett syndrome include hand stereotypies, breathing abnormalities, sleeping difficulties, teeth-grinding and night laughing among others. It is possible that these behaviours may be related to the type of mutation that these girls have. Eight common mutation groupings which are found in Rett syndrome are p.T158M, p.R168X, p.R294X, p.R270X, C-terminal deletions, p.R133C, p.R306C, p.R255X.
What did we do
In this study we compared the behaviours of girls with Rett syndrome in Australia and the UK using a Rett syndrome-specific questionnaire. We also wanted to find out whether any particular behaviours were associated with any specific mutation types.
Information on 145 Australian girls (provided by their families to the Australian Rett Syndrome Database) and 143 UK girls (obtained from a published paper) were used for this study. The girls in this study were between 2 and 19 years of age. Of the 135 Australian girls who had been tested for a MECP2 mutation, just over two thirds had one of the eight common mutations.
What we found
Mutation type did not seem to play a major role in determining behaviour but we noticed that the behaviours of girls with a p.R294X, p.R306C or p.R270X mutation were most different to the others. Girls with any of these three mutations were more likely to have mood difficulties whereas girls with a p.T158M mutation were less like to have mood difficulties.
Those with p.R294X or p.R133C mutations were also more likely to have night-time behaviours and poorer hand function and more frequent hand stereotypies were reported. Girls with R294X mutations were more likely to rock their bodies repeatedly but were also better at walking and standing. Girls with R306C and R133C mutations also seemed to show more fear or anxiety in their daily lives.
What does it mean
There have been few previous reports of emotional and mood problems apart from during the period of regression. This study showed that these changes can continue after the regression period and into adolescence/adulthood. We also showed girls with different mutations can have different sets of behaviours even though all of them are considered to have Rett syndrome. Girls with mutations that are usually associated with milder symptoms (e.g.p.R133C, p.R294X and p.R306C) may be more able to express themselves and therefore, might exhibit more behaviours compared to girls were more severe symptoms.