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I heared on the net that oys can get retts only if a mutation at conception makes him XXY, not XY. is this true? It was on that wrong planet website as a 'radio' braudcast.

That is one way for boys to get Rett's. It's important to distinguish between Rett syndrome (a clinical diagnosis with required diagnostic criteria) and a MECP2 mutation, which can cause Rett syndrome and other developmental disabilities (boys who have a MECP2 mutation may have severe progressive encephalopathy and die early, they may have a cerebral palsy like picture with motor impairments) and adult women may have a learning disability. The course is girls if altered if there is favorable X chromosome inactivation when the embryo is at a few cell stage. By chance, in each cell in each girl has switched off one of the X chromosomes (normal state). If by chance, a girl randomly has shut off most of the X's carrying the MECP2 mutation, then the course may be much milder than expected. If half of the abnormal X's are still active, then that girl will likely have Rett syndrome.

If a boys has XXY, and one of those X's has a MECP2 mutation, then that boy may have Rett syndrome. However, there are only 1-2 such boys ever reported. This may be called "Kleinfelter syndrome" with Rett syndrome.

Boys with XY who have MECP2 mutation may die early as above. There is also a thought that most of the mutated X chromosomes come from the father, meaning that boys, who get their X's from their moms and their Y's from their dad, just don't have MECP2 mutations. No one has demonstrated increased loss of male fetuses, another way to explain girl predominance.144.92.217.101

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