Huntington's Disease Inheritance: 50% Risk for Each Child

Genetic Basis

Huntington's disease (HD) is an autosomal dominant disorder caused by a CAG trinucleotide repeat expansion in the HTT gene on chromosome 4. Only one mutated allele is needed to develop the disease.

Inheritance Probability

• Each child of an affected parent has a 50% chance of inheriting the expanded allele.
• Risk is identical for males and females.
• If the child does not inherit the expansion, they cannot pass HD to their offspring.

Key Features

• Age of Onset: Typically 30–50 years (adult-onset); juvenile onset (<20) occurs with very large repeats.
• Progressive Course: Motor (chorea, dystonia), cognitive, and psychiatric decline over 15–20 years.
• No Cure: Symptomatic management only (tetrabenazine/deutetrabenazine for chorea, antidepressants, antipsychotics, supportive care).

Reproductive Options

• Prenatal Testing: Chorionic villus sampling (CVS) or amniocentesis.
• Preimplantation Genetic Testing (PGT-M): IVF with embryo biopsy to select unaffected embryos.
• Non-disclosure Testing: Prenatal exclusion testing without revealing parental status.

Genetic Counseling Is Essential

All at-risk individuals should receive genetic counseling before conception to understand:

• Testing implications (psychological, insurance, family dynamics).
• Reproductive choices and timelines.
• Presymptomatic testing protocol (if they wish to know their own status).

HD testing is a profound personal decision; professional guidance ensures informed, autonomous choice.