[Clinical variability of Juvenile Huntington's Disease phenotype].

Huntington's disease is rare, genetically determinated, neurodegenerative disorder. It is determined by dynamic mutation of IT15 gene on short arm of 4 chromosome. Characteristic symptomatology include involuntary movements, cognitive decline and wide spectrum of mood and behaviour disorders. It typically becomes noticeable in mid-adult life, but there are reported cases of appaers of symptoms between 2 and 80 year of life. Especially interesting is juvenile Huntington's disease- the Westphal variant with the beginning in childchood (before 20 year of age) because of clinical differences causing diagnostic difficulties. It affects 5-10% of carries of the mutant gene. Symptoms became noticeable before 10 year of age only in 1% of them.