Huntington’s disease is a rare , inherited , neurodegenerative disorder that mainly affects the nervous system . The disease usually appears between 30 and 45 years of age , but in rare cases can exist in a juvenile form with onset before age 20, sometimes people with MH begin to manifest irritability, fatigue , difficulty concentrating , instability. The disease is named by George Huntington , the American doctor who described it for the first time in 1872 , at age 22.
The MH acts on multiple levels :
- Voluntary movements
- Loss of cognitive abilities
- Psychiatric disorders
The gene responsible for HD was identified in 1993 and is located on chromosome 4 , and has been called by a code : EN – 15 . This gene contains the information for the production of a protein that has been called huntingtin . The function of huntingtin is still unknown , although it is shown that it is a protein essential for life People with HD have alterations in the gene for huntingtin , in fact their cells produce an abnormal form of this protein which somehow causes the degeneration of neurons. In the first part of the HTT gene there is a sequence of three nucleotides , cytosine – adenine – guanine ( CAG ) repeated numerous times ( eg . CAG- CAG- CAG- CAG- ….) . This is called ” trinucleotide repeat “.
According to the genetic code the triplet CAG coding for the amino acid glutamine. A repeat trinucleotica up to 35 units sequences CAG is considered normal . When the HD gene It has more than 40 CAG repeats , the abnormal huntingtin protein that is produced causes the disease. It was also noted that the expansion of the triplets is much more likely during the formation of sperm , compared to that of ova . Therefore , the expansion of triplets occurs preferably by his father. Most people with Huntington’s is heterozygous.
This means that they have two copies of the gene different : a normal copy inherited from the unaffected parent and one copy inherited from the pathological affected parent.
It ‘ also a genetic disorder of dominant type . This means that you only need one copy of the abnormal gene , derived from one parent to inherit the disease .
MATTEO GUAGENTI ©