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Huntington’s disease (HD) is a progressive neurodegenerative disorder caused by an expanded CAG repeat in the huntingtin gene, which encodes an abnormally long polyglutamine repeat in the huntingtin protein. The disease is inherited in an autosomal dominant manner with age-dependent penetrance. CAG repeat lengths of 40 or more are associated with nearly full penetrance by age 65 years. HD typically occurs between 35 and 50 years of age. About 6% of cases have juvenile HD, defined as disease onset before the age of 20 (see Chap. 68). In most families, age of onset tends to be similar, but in some families the disease occurs progressively earlier in successive generations, a phenomenon called anticipation.
KeywordsProgressive Neurodegenerative Disorder Predictive Genetic Testing Tongue Protrusion Huntingtin Protein Autosomal Dominant Manner
Huntington’s disease.mp4 (MP4 42,375KB)
Clip 1: the patient exhibits generalized chorea predominantly affecting the hands. Rocking movements of the trunk are present. Gait is slow with upper extremity chorea. Motor impersistence is present with inability to maintain tongue protrusion for longer than 10 s. Clip 2: mild choreiform movements of the fingers and toes are evident in her undiagnosed brother. His gait is normal except for choreiform finger movements. There is no motor impersistence of tongue protrusion.
- 3.Guidelines for the molecular genetics predictive test in Huntington’s disease. International Huntington Association (IHA) and the World Federation of Neurology (WFN) Research Group on Huntington’s Chorea. Neurology 1994;44:1533–6.Google Scholar