MECP2 (methyl-CpG-binding protein-2): An enzyme which, when mutated, results in RTT (Rett syndrome), a genetic disease that is a uniform and striking, progressive neurologic developmental disorder and one of the most common causes of mental retardation in females.
After normal development up to the age of 6 to 18 months, developmental stagnation occurs followed by rapid deterioration of high brain functions. Within 1 to 2 years, this deterioration progresses to loss of speech, severe dementia, behavior reminiscent of autism, stereotypic hand-wringing movements, loss of purposeful use of the hands, jerky ataxia (wobbliness) of the trunk, intermittent hyperventilation, and microcephaly (small head).
Thereafter, a period of apparent stability lasts for decades. But additional neurologic abnormalities intervene insidiously These abnormalities include what is called spastic paraparesis (paralysis and spasticity of the legs) and epilepsy (seizures). A striking deceleration of growth has been found across all measurements in most girls with Rett syndrome who end up with short stature and microcephaly.
The mortality (death) rate among children with Rett syndrome is increased (1.2% per year). A high proportion (26%) of the deaths are sudden and associated with a heart conduction problem, namely an abnormally prolonged QT interval on the electrocardiogram.
Rett syndrome is a most unusual disease because ONLY GIRLS have it. It is an X-linked dominant disorder that is lethal in males. Females who receive the Rett syndrome gene (symbolized RTT) have Rett syndrome. Males who receive the RTT gene apparently die before birth. The RTT gene has been found on the X chromosome in chromosome band Xq28 near the very end of the long (q) arm of the X chromosome. The gene there is a mutated version of the gene encoding methyl-CpG-binding protein-2 (MECP2).
The syndrome that bears his name was first described by Andreas Rett, an Austrian pediatrician, in 1966. The frequency of Rett syndrome -- about 1 in 10-20,000 girls -- appears similar in southwest Sweden, North Dakota, and metropolitan Tokyo.