Parkinson’s Disease

• Inheritance: Approximately 15–20% of early‑onset Parkinson’s cases have an identifiable genetic mutation [1].
• Key Genes:
  • LRRK2: Mutations often autosomal dominant with incomplete penetrance.
  • PARK2 (parkin): Autosomal recessive juvenile Parkinsonism.
  • GBA: Heterozygous variants increase risk and can modify disease course [2].

Dystonia

• DYT1 (TOR1A): Classic early‑onset torsion dystonia, autosomal dominant with ~30% penetrance [3].
• THAP1: Associated with adult‑onset primary dystonia.

Did you know? Primary dystonias affect about 1 in 2,500 individuals, and genetic forms often present in childhood or early adulthood.

Huntington’s Disease

• Inheritance: Autosomal dominant CAG repeat expansion in the HTT gene.
• Phenotype: Progressive chorea, cognitive decline, psychiatric features.
• Predictive Testing: Available for at‑risk adults; requires extensive pre‑ and post‑test counseling [4].

Spinocerebellar Ataxias (SCAs)

• Mechanism: Multiple subtypes (e.g., SCA1, SCA3) caused by repeat expansions or point mutations.
• Inheritance: Mostly autosomal dominant.
• Testing: Repeat‑expansion assays provide definitive diagnosis [5].

Wilson Disease

• Gene: ATP7B, autosomal recessive copper‑transport defect.
• Relevance: Treatable if diagnosed early; genetic testing confirms carrier and affected status [6].
• Read more about Wilson disease in our previous blog post.

• Early Onset: Symptoms before age 50, or juvenile presentation in Parkinsonism or dystonia.
• Family History: Multiple affected relatives or known genetic diagnosis.
• Atypical Features: Rapid progression, poor response to standard therapy, or additional neurological signs.
• Reproductive Planning: Conditions like Huntington’s where future generations face 50% risk per pregnancy [4].

1. Comprehensive Family History: A three‑generation pedigree identifies inheritance patterns and informs test selection.
2. Risk Assessment: Counselors explain autosomal dominant, recessive, or X‑linked risks in patient‑friendly terms.
3. Pre‑Test Counseling: Clarifies the scope of testing, what it can detect, limitations, and possible outcomes (including VUS) [7].
4. Post‑Test Support: Interpreting results, discussing implications of pathogenic, benign, or uncertain variants, and guiding next steps.
5. Family Communication: Strategies for sharing results with at‑risk relatives, respecting patient autonomy.

For more on the genetic counseling process, see Understanding the Genetic Counseling Process: A Comprehensive Guide.

• Panel Testing: Multi‑gene panels target known movement‑disorder genes, offering efficient, cost‑effective analysis [8].
• Whole Exome Sequencing (WES): Broad approach when phenotype overlaps multiple conditions; yields diagnoses in ~30% of undiagnosed neurologic cases [9].
• Repeat‑Expansion Testing: Essential for Huntington’s and SCAs; uses PCR or Southern blot methods.
• Predictive vs. Diagnostic Testing: Predictive for asymptomatic at‑risk adults (e.g., HD), diagnostic for symptomatic individuals.

Selecting the right test for you is a very crucial aspect, and your genetic counselor will help you understand the available options for you to make an informed decision.

• Anxiety & Uncertainty: Awaiting results or dealing with VUS can be distressing; counselors provide coping strategies and referrals to support groups.
• Guilt & Family Dynamics: Patients may feel guilt over passing mutations; counseling fosters open communication and family support.
• Autonomy & Consent: Especially vital in predictive testing, patients decide if and when to learn their status, with no pressure.

Did you know? Predictive testing for Huntington’s requires mandatory psychological evaluation in many protocols to ensure patient readiness [4].

Genetic counseling for movement disorders bridges cutting‑edge science and patient‑centered care. By elucidating genetic risks, guiding appropriate testing, and supporting emotional needs, counselors empower individuals to navigate diagnosis and family planning with confidence.