Genetic Counselor - Your role as the genetic counselor is to find out what types of treatment there are for the disorder and how you can advise these parents on the disorder that their child has. Also, find out how the child inherited the disease. Is it dominant, recessive, sex-linked, etc?

The frequency of occurring of this disease is approximately 4-7:100000
This disease is inherited autosom dominant.
The course:
· The course is slow and progressing
· The disease starts, mostly, in the age of 30-50
· In the next generations can occur earlier
· First symptom is stupor, but sometimes it can be also involuntarily

Treatment
  • There is no casual treatment
  • Symptomatic treatment
only move symptoms can be treated


Inheritance

external image 270px-Autosomal_Dominant_Pedigree_Chart2.svg.pngexternal image magnify-clip.png HD is inherited in an autosomal dominant fashion. Each successive generation is given a roman numeral I, II, or III. Note that the probability of the offspring of an affected individual being affected (red) themselves is 50%, however if they receive the affected parent's normal allele, they and all of their offspring are unaffected (blue). Transmission from an affected father to an affected son rules out X-linked inheritance.
Huntington's disease is inherited autosomal dominantly, meaning that an affected individual typically inherits a copy of the gene with an expanded trinucleotide repeat (the mutant allele) from an affected parent. In this type of inheritance pattern, each offspring of an affected individual has a 50% chance of inheriting the mutant allele and therefore being affected with the disorder (see figure). It is extremely rare for Huntington's disease to be caused by a de novo mutation,[23[[http://en.wikipedia.org/wiki/Huntington%27s_disease#cite_note-22|]]][24[[http://en.wikipedia.org/wiki/Huntington%27s_disease#cite_note-23|]]] approximately 10% of patients inherit a chromosome that underwent CAG expansion from an unaffected parent with <36 CAG repeats[25[[http://en.wikipedia.org/wiki/Huntington%27s_disease#cite_note-pmid19249009-24|]]], however, the inheritance of HD is more complex due to potential dynamic mutations, where DNA replication does not produce an exact copy of the trinucleotide repeat. This can cause the number of repeats to change in successive generations, such that an unaffected parent with an "intermediate" number of repeats (28-35), or "reduced penetrance" (36-39), may pass on a copy of the gene with an increase in the number of repeats that produces fully penetrant HD.[26[[http://en.wikipedia.org/wiki/Huntington%27s_disease#cite_note-pmid9063751-25|]]] These new mutations have occurred in less than 10 percent of people with HD, but explain the origins of the disorder.[27[[http://en.wikipedia.org/wiki/Huntington%27s_disease#cite_note-26|]]] Maternally inherited alleles are usually of a similar repeat length, whereas paternally inherited ones seem to have a higher chance of increasing in length.[28[[http://en.wikipedia.org/wiki/Huntington%27s_disease#cite_note-27|]]] Increases in the number of repeats (and hence earlier age of onset and severity of disease) in successive generations is known as genetic anticipation.
Homozygous individuals, who have two affected genes, are very rare except in large consanguineous families. While HD seemed to be the first disease found for which homozygotes did not differ in clinical expression or course from typical heterozygotes,[29[[http://en.wikipedia.org/wiki/Huntington%27s_disease#cite_note-pmid2881213-28|]]] more recent analysis suggests that homozygosity affects the phenotype and the rate of disease progression but does not alter the age of onset, suggesting that the mechanisms for these factors differ.[30[[http://en.wikipedia.org/wiki/Huntington%27s_disease#cite_note-29|]]] Also polymorphism located within PGC-1alpha gene explains a small, but statistically significant, amount of the variability in age at onset of the disease[21[[http://en.wikipedia.org/wiki/Huntington%27s_disease#cite_note-pmid19200361-20|]]]