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Huntington’s disease (HD) is an autosomal-dominantly inherited neurodegenerative disorder. It has a prevalence of 5–7 per 100,000 people in European and North American populations.1 The first symptoms typically appear between the ages of 35 and 45 years and include minor uncontrollable movements and personality changes such as depression and irritability.1
Initially, motor symptoms mainly involve the small distal muscles, but later on the larger postural muscles also become affected, resulting in the characteristic choreatic movements. Over the years, cognitive functions gradually deteriorate leading to impairments in memory and attention. Progressive weight loss and muscle wasting, despite sustained or even increased caloric intake, are also hallmarks of the disease.2–4 The end stage of the disease is characterised by rigidity, dystonia, dementia and cachexia. In most cases, HD results in death about 15–20 years after clinical onset. HD is caused by an expanded sequence of a cytosine-adenine-guanine (CAG) repeat located near the 5’ end of the first exon of the huntingtin (HTT) gene.5 Healthy individuals typically have fewer than 36 CAG repeats, and repeats of 40 or more cause HD with complete penetrance.5 Individuals with 36–39 CAG repeats are at risk of developing HD, but penetrance is often incomplete.6 There is an inverse association between the length of the mutant CAG expansion and age of onset, which is modulated by the size of the CAG repeat tract in the normal allele,7 as well as by other genetic and environmental factors.8,9
Although less well-known, autonomic nervous system (ANS) dysfunction can also accompany HD.2 Indeed, vegetative symptoms indicative of ANS dysfunction have repeatedly been reported in patients with HD and include hyperhydrosis, micturition and swallowing difficulties,10–12 sexual dysfunction13 and complaints suggestive of orthostatic intolerance.14,15 Vegetative symptoms are most prominent in the advanced stages of the disease,16,17 but autonomic complaints such as dizziness following standing up, excessive perspiration and tachycardia can occur even in mildly disabled HD patients (i.e. Shoulson and Fahn stages I and II), as well as in otherwise asymptomatic gene carriers.18–20