Diagnosis, Risks, Inheritance And Genetic Testing

12.2.07

Making referral to clinical genetics
• Positive family history, ?syndrome.
• Worried, when asked, planning children.
• Tell family about referral.
• Diagnosis, family history, age, investigations so far.
• What family know already etc.

Huntington's disease
• Autosomal dominant, 50% risk of transmission.
• Variable age of (adult) onset: 30s-50s.
• Anticipation, especially from father.
• Gene (triplet repeat) on chromosome 4p.
• Involuntary movements, tremor, chorea.
• Change of personality, drive.
• Behavioural changes.
• Psychiatric symptoms.

Diagnostic and predictive tests
• In presence of symptoms.
• Unaffected, but wants to know.
• Testing of foetus during pregnancy (at-risk parent knows their status).
• Excluding risk of Huntington's disease in foetus (at-risk parent does not want to know their status).

Issues in predictive genetic testing
• Testing asymptomatic for late-onset conditions.
• To know or not to know?
• Is there useful intervention?
• Possible harmful psychological effects.
• Insurance and employment issues.
• Does not predict age of onset/severity etc.

X (sex)-linked inheritance
• Women = carriers.
• Men affected (knight's move).
• No male-to-male transmission.

What can the Human Genome Project deliver?
• Genetic diagnosis, understanding process.
• Novel treatments, gene therapy.
• Miscarriage, infertility, organ transplantation.
• Dementia, heart disease, cancer.
• Genetically-produced drugs, gene therapy.
• Stem cells for transplantation.
• Information, ethical and practical dilemmas.

• SNPs - single-nucleotide polymorphisms.
• UK Biobank.