Huntington's Disease: The Genetic Brain Condition That Strikes in the Prime of Life

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder — caused by a CAG trinucleotide repeat expansion in the HTT gene (chromosome 4). Every child of an affected parent has a 50% risk of inheriting the mutation. If inherited, HD is fully penetrant — the disease will inevitably develop, typically between ages 30 and 50, though juvenile-onset (before 21) and late-onset (after 60) forms exist. This certainty — and the 20–25 year interval between genetic test result and potential symptom onset — creates profound psychological and ethical challenges for families.

Clinical Features — The Triad

Movement disorder (chorea): The most visible feature — irregular, flowing, "dance-like" involuntary movements affecting the face, trunk, and limbs. Initially subtle and mistaken for fidgeting; progressively worsening over years. Swallowing becomes impaired (choking and aspiration pneumonia — a major cause of death). Cognitive decline (dementia): A "subcortical" dementia — processing speed slows first; executive function (planning, set-shifting) deteriorates; memory for procedures is affected more than episodic memory. Psychiatric symptoms: Depression (most common psychiatric manifestation; elevated suicide risk); apathy (difficulty initiating activity); irritability and aggression; obsessive-compulsive features; rarely psychosis. Psychiatric symptoms often predate the movement disorder by years.

Genetic Testing

Confirmatory testing: PCR analysis of the HTT CAG repeat. 40+ repeats = definite HD; 36–39 = reduced penetrance. Predictive testing (testing a healthy at-risk person before symptoms) requires extensive pre-test genetic counselling — psychologically complex. Preimplantation genetic diagnosis (PGD) is available for couples wanting children without transmitting the mutation.

Treatment

No disease-modifying treatment yet (as of 2026); RNA-targeting approaches in clinical trials are the greatest hope. Symptomatic management: tetrabenazine or valbenazine for chorea; antidepressants for depression; antipsychotics for psychiatric symptoms; speech therapy; physiotherapy; dietitian for weight maintenance (HD dramatically increases metabolic rate). Sri Anand CNC, Chanda Nagar, Hyderabad. Call +91 90633 66983.