Signs and Symptoms of Huntington's Disease
Huntington's disease presents with a characteristic triad of choreic movements, cognitive decline, and psychiatric changes, typically beginning in mid-life, though psychiatric and cognitive symptoms often precede motor manifestations by up to 15 years. 1
Motor Symptoms
The hallmark motor feature is chorea - involuntary, irregular, dance-like movements that progressively worsen over time. 1 These choreiform movements are accompanied by:
- Dysarthria (speech difficulties)
- Dysphagia (swallowing problems)
- Progressive motor impairment affecting coordination and balance
Juvenile-Onset Variant (5% of cases)
In patients presenting before age 20, the motor phenotype differs dramatically:
- Rigidity and spasticity (rather than chorea)
- Rapidly progressive course
- Earlier and more severe intellectual decline 1
Cognitive Symptoms
Progressive cognitive impairment is a core feature, manifesting as:
- Executive dysfunction
- Memory problems
- Slowed processing speed
- Progressive dementia
These cognitive symptoms frequently appear 15 years before motor onset, making them critical early diagnostic markers. 2
Psychiatric and Behavioral Symptoms
Psychiatric manifestations are extremely common and often the first presenting symptoms, appearing years before motor signs:
- Apathy (most common)
- Depression
- Anxiety
- Obsessive-compulsive symptoms
- Psychosis (in some cases)
- Aggression and irritability 3
Critical Clinical Pitfall
HD is likely underdiagnosed because many patients present with isolated psychiatric symptoms for prolonged periods before motor signs emerge. 2 Any patient with unexplained psychiatric symptoms combined with subtle cognitive decline should prompt consideration of HD, even without family history (15% are spontaneous mutations). 2
Systemic and Autonomic Symptoms
Beyond the classic triad, HD causes widespread systemic dysfunction:
- Weight loss (progressive and often severe) 2
- Cardiovascular dysfunction
- Respiratory problems
- Gastrointestinal symptoms
- Urinary dysfunction
- Sexual dysfunction
- Abnormal sweating 4
These systemic symptoms do not always correlate with CAG repeat length or primary HD symptom severity, indicating independent pathophysiological mechanisms. 4
Neuropathological Basis
Symptoms result from selective neuronal loss, most notably in the caudate nucleus and putamen, explaining the predominance of movement disorders and executive dysfunction. 1
Diagnostic Approach
When HD is suspected based on this symptom constellation:
- Genetic testing for CAG repeat expansion in the huntingtin gene is diagnostic
- ≥40 CAG repeats = fully penetrant disease (100% specific)
- 36-39 repeats = variable penetrance (reduced penetrance alleles)
- ≤35 repeats = not associated with HD phenotype 1
The combination of progressive chorea, cognitive decline, psychiatric symptoms, and weight loss should immediately trigger HD genetic testing, regardless of family history. 5, 2