[Clinical and genetic study of juvenile form of Huntington's disease]

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder caused by high instability and extension of CAG sequences within the coding region of IT15 gene. It affects both sexes and age at onset of the disease may be different but usually occurs in midlife. The term Juvenile Huntington's disease is generally applied to 10% of the cases with onset before 20. We present clinical features and results of DNA analysis in 16 patients from 14 families aged 9 to 36. The age of onset was between 5 to 20 years; duration of the disease was from 2 to 16 years. In 10 cases the mutated gene was transmitted by the affected father; only in two cases by the mother. In all cases anticipation manifested by earlier onset of the disease in subsequent generations and expansion of CAG repeats was documented. The number of CAG repeats was between 50 and 92 (mean 67.3). Progressive mental deterioration, declining school performance, hyperactivity and emotional disturbances were the first symptoms of juvenile HD. Neuropsychological assessment showed mean IQ in Wechsler test 59.6 and Mini-Mental State Examination scores 22.8. Rigidity and bradykinesia were predominant features in the cases with juvenile onset, the remaining ones developed choreatic movements. Three persons had epileptic seizures; two (both females) revealed behaviour and psychiatric disturbances. Amplitudes of somatosensory evoked potentials, visual evoked potentials and brainstem auditory evoked potentials were markedly reduced. MRI of the brain showed atrophy of heads of the caudate nuclei, putamen and globus pallidus.