An In-Frame LMNA Deletion, Sudden Death, and a Pacemaker: When a VUS Meets a Family History
A 34-year-old man is evaluated for dilated cardiomyopathy (ejection fraction 30%) with no ischemic, toxic, or viral explanation. A 12-gene cardiomyopathy panel reports a heterozygous in-frame deletion in LMNA, removing one conserved residue in the rod domain. The laboratory classifies it as a variant of uncertain significance: it is absent from gnomAD, computational predictors are damaging, but functional data are unavailable. Family history: his father died suddenly at 48, a sister required a pacemaker at 42, and his mother is healthy at 70. The proband has first-degree AV block on ECG. He asks whether the result “proves” the family has a genetic disease and whether his 8-year-old son should be tested. The laboratory offers no reclassification without additional data.
1. How should the variant be classified now, and what evidence would justify reclassification? Show the reasoning, including the limits of segregation in this family.
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Current classification should remain variant of uncertain significance (VUS). Under ACMG/AMP criteria, an in-frame deletion can be scored as PM4 (protein length change), absence from gnomAD as PM2_supporting, and computational predictions as PP3_supporting. These are weak criteria and do not reach likely pathogenic. The family history is suggestive but insufficient: the father is deceased and unavailable for testing, and only one affected relative (the sister) can be tested. A single affected carrier does not establish co-segregation; PP1 requires multiple affected meioses, and it is weakened if an unaffected carrier is found. Reclassification would require stronger evidence, such as the sister testing positive plus a second affected relative, functional studies showing abnormal lamin A/C function, a de novo occurrence in an affected individual, or variant-specific case-control enrichment. Until then, the result should not be treated as pathogenic for reproductive decisions.
2. Does the result change clinical management for the proband or his relatives? Outline specific management and testing recommendations.
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Management should be phenotype-driven, not determined solely by the VUS label. The proband already has DCM with reduced EF and first-degree AV block, and LMNA-related cardiomyopathy carries a high risk of conduction disease and ventricular arrhythmia. He needs electrophysiology evaluation, ambulatory ECG monitoring, and consideration of an implantable cardioverter-defibrillator based on LVEF, NSVT, sex, and non-missense variant status. His sister with a pacemaker should be offered LMNA testing; if she carries the variant, she needs cardiac surveillance and arrhythmia risk assessment regardless of the VUS label. The father’s sudden death supports a familial arrhythmia syndrome. The mother is not at risk if the variant is paternal. Because the variant is a VUS, relatives should receive genetic counseling about uncertainty, and management should be based on their own cardiac phenotype and family history.
3. What do you tell him about testing his 8-year-old son?
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I would recommend against predictive testing in childhood at this point. The variant is a VUS, so a positive result would not reliably predict disease and could cause harm through labeling and anxiety. Even if the variant were reclassified as pathogenic, LMNA cardiomyopathy is typically adult-onset, and surveillance in childhood has not been shown to improve outcomes. The son should receive routine pediatric care and be told age-appropriate information about the family history. When he reaches adolescence or adulthood, he can decide about testing and cardiac surveillance. If the variant is later reclassified and an early surveillance program becomes evidence-based, that recommendation can be revisited.