For a mother with hypertrophic obstructive cardiomyopathy treated with alcohol septal ablation, what genetic testing should be offered to her four children?

Genetic Testing for Children of a Mother with HOCM

You should first undergo genetic testing yourself (the mother with HOCM), and if a pathogenic or likely pathogenic variant is identified, then offer cascade genetic testing to all four of your children. 1

Step-by-Step Approach

1. Test the Mother First (Index Case)

The 2024 AHA/ACC guidelines are explicit: genetic testing must start with the affected individual (you, the proband) who has clear phenotypic evidence of HCM 1. Testing should include a panel of the 8 sarcomere genes with strong evidence: MYH7, MYBPC3, TNNI3, TNNT2, TPM1, MYL2, MYL3, and ACTC1 1.

• Yield: Approximately 60-70% chance of identifying a pathogenic variant if you have a family history, or 30-50% if you don't 2
• Important: Testing phenotype-negative relatives (your children) without first identifying your genetic variant has very low yield and won't change clinical management recommendations 1

2. If Your Test is POSITIVE (Pathogenic/Likely Pathogenic Variant Found)

Offer cascade genetic testing to all four children 1. This is the most critical recommendation because:

• Each child has a 50% chance of inheriting the disease-causing variant (autosomal dominant inheritance) 1
• Children who test positive need ongoing cardiac surveillance with ECG and echocardiography to monitor for disease development
• Children who test negative can be released from lifelong clinical surveillance and require no further cardiac follow-up 1, 3

Key benefit: This definitively identifies which children are truly at risk versus those who can be reassured they will never develop HCM from this genetic cause.

3. If Your Test is NEGATIVE or Shows Only Benign Variants

Do NOT perform genetic testing on your children 1, 3. Instead:

• All four children require ongoing clinical screening with ECG and echocardiography
• Screening frequency: every 1-2 years during childhood/adolescence, as clinical HCM can develop in 5-10% at first screening and another 3-5% before age 18 4
• Continue screening into adulthood, as phenotype conversion can occur in young adults 4

4. If Your Test Shows a Variant of Uncertain Significance (VUS)

A VUS is not clinically actionable 1. Treat this the same as a negative result:

• Do not test your children for the VUS
• All children need continued clinical screening
• Family member testing may only be considered in select research circumstances with cardiovascular genetics expert guidance 1

Critical Pitfalls to Avoid

1. Don't test children first: Testing starts with you, not your children 1
2. Don't skip genetic counseling: Pre- and post-test genetic counseling is essential to discuss psychological, social, and insurance implications 1, 5
3. Don't assume negative genetic testing means no risk: If you test negative, your children still need clinical surveillance because 30-40% of HCM cases don't have identifiable sarcomere variants 1
4. Reinterpretation matters: Variants can be reclassified over time (10-15% are reclassified), so if a pathogenic variant is later downgraded, children released from surveillance must be notified and screening recommenced 1, 6

Special Considerations for Children

• In pediatric patients, sarcomeric variants are more closely associated with sudden cardiac death risk 1
• Children with multiple pathogenic variants (which occurs in up to 25% of pediatric HCM cases with identified mutations) may have more severe disease 7
• Clinical HCM can develop early, with some children requiring medical, surgical, or device therapy before age 18 4