To create a protein from a gene, the gene needs to be expressed (switched on) to become active and later silenced (switched off). Expressing a gene occurs by a process called "acetylation" and silencing the gene occurs by the reverse process of "deacetylation". Now, acetylation is performed by a family of proteins called histone acetyltransferases (HAT); deacetylation is performed by another family of proteins called histone deacetylases (HDAC).
To create a protein then we need to acetylate (switch on) the gene first. The acetylated parts of the "gene" are actually the H2A and H2B histones of the nucleosome. This allows gene expression to commence, resulting in the manufacture of the corresponding protein.
Two important members of the HAT family are the CREBBP and EP300 proteins, manufactured from the correspondingly named genes. Any malfunction in these two genes will cause problems in the process of creating many of the body's proteins. And guess what? These are the very same genes associated with RTS. RTS is usually caused by a malfunction (due to mutation) of the CREBBP or EP300 genes. Approximately 63% of people with RTS have a mutation in one of these two genes.
So there you are. A fairly detailed explanation of what probably causes RTS in your child. How does that help?
From a day-to-day perspective, not much. But it's worth keeping an eye open for new clinical trials or drugs that might help alleviate the symptoms of RTS. I've included some links in the panel on the right to important sites that will inform you of new developments; particularly OrphaNews and Clinical Trials (US).