Huntington's Disease

UPSC Relevance: Health Care

What is it?

Huntington's disease is a progressive neurodegenerative genetic disorder.

It causes:

  • Involuntary movements

  • Cognitive decline

  • Psychiatric/behavioral abnormalities

Chorea is a characteristic movement abnormality.

Genetics

  • Caused by mutation in the HTT gene.

  • Located on chromosome 4.

  • It is an autosomal dominant disorder.

  • Involves CAG trinucleotide repeat expansion.

Pathology

There is progressive degeneration, particularly of:

  • Caudate nucleus

  • Putamen

  • Other basal ganglia structures

Clinical Triad

Remember:

M-C-P

  • Motor → chorea

  • Cognitive → dementia/cognitive decline

  • Psychiatric → depression, irritability, behavioral changes

Genetic Principle

Because it is autosomal dominant:

  • One affected heterozygous parent can transmit the mutation to approximately 50% of offspring.

UPSC/Medical Exam Pointer

Huntington's demonstrates anticipation, particularly through paternal transmission, due to increasing CAG repeats.

Prelims Trap: Huntington's is not autosomal recessive.