Huntington's disease

ABSTRACT

Huntington disease [HD] is an inherited disorder of central nervous system it is a autosomal dominant disease causing progressive neurodegeneration that leading to uncontrolled movements, mental and emotional problems, and loss of thinking ability [cognition]. HD can occur at any age but the mean onset is between 35 to 44 years, generally the onset of disease depending on allele size. A mutation occur on HD gene leading to trinucleotide repeat expansion [increase number of AG codon over 40 repeated] which lead to produce a mutant form of huntingtin protein that cause cell death in selective area in brain [basal ganglia]. The most probable mechanism that explains the expansion mutation is Unequal crossing over and Polymerase slippage. The incidence of HD is varies depend on type or descent of a population weather they are western European, Japanese, Chinese or African blacks, this variation due to the genetic risk factor and the variation on the HD gene. About two-thirds of affected individuals present with neurological manifestations, while others present with psychiatric changes, the manifestations start with subtle changes in coordination, minor involuntary movements and develop to increasing difficulty with voluntary activity and chorea and at the end motor disability becomes severe and the individual is often totally dependent and mute. Therapy that stop or slow the neurological degeneration is unavailable but drugs are used to alleviate the patient suffering by managing certain symptoms such as chorea, psychosis, and depression. The diagnosis is usually by the presence of clinical manifestation and family history and confirmed by molecular genetic testing which also used to predictive testing and prenatal diagnosis