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[ Home ](https://mdster.com) 2. [ Blog ](https://mdster.com/blog) 3. [ Medical Education ](https://mdster.com/blog?category=medical-education) 4. VUS Counseling in Pediatrics: How to Interpret Uncertain Variants [ Medical Education ](https://mdster.com/blog?category=medical-education) VUS Counseling in Pediatrics: How to Interpret Uncertain Variants =================================================================== A practical guide to ACMG classification, family studies, and safe counseling when a pediatric report shows a variant of uncertain significance. [ MDster Editorial Team ](https://mdster.com/about) · May 02, 2026 · 7 min read · 26 [ Reviewed by Dr. Ali Ragab, MBBCH, MSc, MCAI ](https://mdster.com/medical-reviewers/dr-ali-ragab) [Editorial Policy](https://mdster.com/editorial-policy) | [Corrections Policy](https://mdster.com/corrections) [ Board Review ](https://mdster.com/blog?tag=board-review) [ Pediatrics ](https://mdster.com/blog?tag=pediatrics) [ Pediatric Genetics ](https://mdster.com/blog?tag=pediatric-genetics) [ Variant Interpretation ](https://mdster.com/blog?tag=variant-interpretation) [ Genetic Counseling ](https://mdster.com/blog?tag=genetic-counseling) ![VUS Counseling in Pediatrics: How to Interpret Uncertain Variants](https://mdster.com/storage/blog/images/vus-counseling-in-pediatrics-how-to-interpret-uncertain-variants.jpg) Share this article Share this post The dangerous mistake in pediatric genetics is not missing the pathogenic variant. It is overcalling the uncertain one. The infant with epilepsy, the child with cardiomyopathy, and the toddler with syndromic developmental delay all tempt you to treat a **VUS** as an answer. Don't. A **variant of uncertain significance** is an evidence problem, not a diagnosis, and boards love this distinction because bad counseling here causes real harm. [\[1\]](#cite-1 "Reference [1]") Start With the ACMG Framework, Not Your Gut ------------------------------------------- Current clinical reporting still rests on the ACMG/AMP five-tier framework: **pathogenic, likely pathogenic, uncertain significance, likely benign, benign**. The classification is built from weighted evidence such as population frequency, computational prediction, functional studies, and segregation data. The “likely” categories were intended to mean **greater than 90% certainty**, not a vague hunch. When evidence is insufficient or conflicting, the right landing zone is VUS. [\[1\]](#cite-1 "Reference [1]") That last point matters. **Conflicting evidence defaults to uncertain significance**, and that is not a failure of the lab. It is the system doing exactly what it should do: stopping you from converting plausibility into certainty. Board pitfall: a phenotype match does **not** magically upgrade a VUS. Phenotype can strengthen interpretation, but only within the formal evidence rules. [\[1\]](#cite-1 "Reference [1]") ClinGen has continued to refine how ACMG criteria are applied, with current variant-classification guidance updated through **July 2025** and linking to criteria-specific recommendations such as de novo evidence and PP1/BS4 segregation guidance. Translation: the ACMG framework is the scaffold, but gene- and disease-specific specifications often decide how persuasive a piece of evidence really is. [\[2\]](#cite-2 "Reference [2]") Use the report like this: CategoryWhat it meansHow to act**P/LP**Evidence is sufficient or near-sufficientCan support diagnosis in the right phenotype**VUS**Evidence is insufficient or conflictingDo **not** use alone for management or predictive testing**LB/B**Evidence argues against causationDo not use to explain the phenotype That is the practical management split the ACMG framework is trying to enforce. [\[1\]](#cite-1 "Reference [1]") Counseling the Family Without Creating False Certainty ------------------------------------------------------ Say it plainly: *We found a DNA change, but today we cannot say whether it explains your child's condition.* Then separate the **variant** from the **phenotype**. Keep treating the child in front of you. If the child has seizures, hyperammonemia, hypertrophic cardiomyopathy, or a recognizable dysmorphic pattern, manage those findings on their own merits. The VUS may become relevant later; it does not earn clinical authority today. [\[1\]](#cite-1 "Reference [1]") The highest-yield counseling sentence is simple: **do not use a VUS for irreversible or predictive decisions.** That means no syndrome-specific surgery because of the variant alone, no false reassurance that surveillance can stop, and no labeling siblings as affected or unaffected on the basis of the VUS. ACMG is explicit that a VUS should not drive clinical decision-making, although extra monitoring may be reasonable when the **phenotype itself** remains concerning. [\[1\]](#cite-1 "Reference [1]") Then make the follow-up plan explicit before the visit ends. Tell the family who owns re-review, what new information matters, and when to come back. ACMG recommends clear laboratory reanalysis policies and **periodic inquiry** by clinicians when a VUS has been reported and no proactive update has been issued. There is no universal interval mandated by the guideline, so use a local system and document it. [\[1\]](#cite-1 "Reference [1]") > **Clinical Pearl:** A VUS may justify more data collection. It does **not** justify more certainty. [\[1\]](#cite-1 "Reference [1]") Segregation Analysis: Order Family Testing Only if It Can Change the Call ------------------------------------------------------------------------- Family testing is useful only when it is **informative**. For a suspected dominant pediatric disorder, start with affected relatives, not a reflexive fishing expedition in everyone. Co-segregation with disease can support **PP1**; lack of segregation in an affected relative can support **BS4**. But this is where trainees get burned: reduced penetrance, variable expressivity, age-dependent onset, phenocopies, and bad phenotyping can all distort segregation logic. ClinGen guidance emphasizes that only **affected individuals** count toward PP1, and BS4 requires careful evaluation of affected non-segregating relatives. [\[3\]](#cite-3 "Reference [3]") In children, trio testing is especially powerful because it can upgrade a hand-wavy “probably de novo” story into formal evidence. ClinGen's **PS2/PM6** framework gives more weight when parentage is confirmed, the phenotype is specific for the gene, and the same de novo observation occurs in multiple unrelated probands. The strength drops when parentage is unconfirmed or the phenotype is nonspecific. That is why the exact same variant can feel much more convincing in one child than in another. [\[4\]](#cite-4 "Reference [4]") Reclassification: What Actually Moves a VUS ------------------------------------------- Most VUS reclassification does not happen because somebody stares harder at the report. It happens because the evidence changes: richer phenotype data, better family segregation, confirmed de novo status, functional or RNA studies, updated population databases, and gene-specific ClinGen specifications. ACMG explicitly notes that added family testing can reclassify variants, and that growing population datasets have already pushed many uncertain variants toward benign. [\[1\]](#cite-1 "Reference [1]") So teach families the right mental model: a VUS is a **temporary evidence state**. It may move toward benign, it may move toward pathogenic, or it may stay unresolved for years. Your job is not to predict which one will happen. Your job is to preserve good medicine while the genetics catches up. [\[1\]](#cite-1 "Reference [1]") Clinical Correlations --------------------- In practice, the child with hypertrophic cardiomyopathy is managed as cardiomyopathy because of the **echo and exam**, not because a sarcomere-gene VUS appeared on a panel. The infant with hyperammonemia is treated as a metabolic emergency because the **biochemistry** demands it, not because sequencing found an uncertain variant. And the asymptomatic sibling should not undergo predictive management for a VUS unless the genetics team is using targeted testing specifically to clarify segregation. That is safe pediatrics and classic board logic. [\[1\]](#cite-1 "Reference [1]") Key Takeaways ------------- - **VUS means insufficient or conflicting evidence**, not “probably disease.” [\[1\]](#cite-1 "Reference [1]") - **ACMG/AMP uses five categories**, and likely pathogenic/likely benign imply **>90% certainty**. [\[1\]](#cite-1 "Reference [1]") - **Do not use a VUS alone for treatment, prognosis, or predictive family testing.** [\[1\]](#cite-1 "Reference [1]") - **Order family studies only when they can clarify segregation or de novo status.** [\[3\]](#cite-3 "Reference [3]") - **Plan re-review**, because phenotype updates, family data, and new evidence can reclassify the variant. [\[1\]](#cite-1 "Reference [1]") Conclusion ---------- Residents get in trouble when they confuse possibility with proof. Treat the child, not the ambiguity. Use the ACMG framework, collect only informative family data, and give families a concrete follow-up plan. If you do that, a VUS becomes manageable uncertainty instead of bad medicine. [\[1\]](#cite-1 "Reference [1]") Frequently Asked Questions ---------------------------- ### When is parental testing worth ordering after a VUS result? Order it when it can clarify **de novo status** or **segregation**. Avoid reflex testing of relatives if the result will not change classification or management. [\[4\]](#cite-4 "Reference [4]") ### Can a VUS be used for predictive testing in siblings? Not for routine predictive management. Family testing is appropriate only if the genetics team is using it to help classify the variant. [\[1\]](#cite-1 "Reference [1]") ### How often should a VUS be reviewed? ACMG recommends **periodic inquiry** and clear reanalysis policies, but it does not set one universal interval. Re-review sooner if new phenotype or family data emerge. [\[1\]](#cite-1 "Reference [1]") ### What kinds of evidence most often reclassify a VUS? Segregation data, confirmed de novo events, functional or RNA studies, updated population frequency, and newer ClinGen gene-specific specifications are the usual drivers. [\[1\]](#cite-1 "Reference [1]") ### Does a strong phenotype match make a VUS actionable? No. A tight phenotype can strengthen interpretation, but a VUS remains non-diagnostic until the evidence crosses formal classification thresholds. [\[3\]](#cite-3 "Reference [3]") References (9) ------------------ 1. 1. [ www.acmg.net/docs/standards\_guidelines\_for\_the\_interpretation\_of\_sequence\_variants.pdf?source=post\_page--------------------------- ](https://www.acmg.net/docs/standards_guidelines_for_the_interpretation_of_sequence_variants.pdf?source=post_page---------------------------) [↩](#cite-ref-1-1 "Back to text") 2. 2. [ clinicalgenome.org/tools/clingen-variant-classification-guidance ](https://clinicalgenome.org/tools/clingen-variant-classification-guidance/) [↩](#cite-ref-2-1 "Back to text") 3. 3. [ pmc.ncbi.nlm.nih.gov/articles/PMC10806742 ](https://pmc.ncbi.nlm.nih.gov/articles/PMC10806742/) [↩](#cite-ref-3-1 "Back to text") 4. 4. [ www.clinicalgenome.org/site/assets/files/3461/svi\_proposal\_for\_de\_novo\_criteria\_v1\_1.pdf ](https://www.clinicalgenome.org/site/assets/files/3461/svi_proposal_for_de_novo_criteria_v1_1.pdf) [↩](#cite-ref-4-1 "Back to text") 5. 5. Richards S, et al. Standards and guidelines for the interpretation of sequence variants. Genetics in Medicine. 2015. 6. 6. Deignan JL, et al. Points to Consider in the Reevaluation and Reanalysis of Genomic Test Results: A Statement of the ACMG. Genetics in Medicine. 2019. 7. 7. Biesecker LG, et al. ClinGen guidance for use of the PP1/BS4 co-segregation and PP4 phenotype specificity criteria. American Journal of Human Genetics. 2024. 8. 8. ClinGen Sequence Variant Interpretation Recommendation for de novo Criteria (PS2/PM6), Version 1.1. 9. 9. ClinGen Variant Classification Guidance, updated July 2025. 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