| Domain | Established finding | Quantitative evidence | Evidence type / source / date | Knowledge-base ontology suggestions |
|---|---|---:|---|---|
| Definition / triad | Andersen-Tawil syndrome (ATS) is a rare inherited ion-channel disorder classically defined by ventricular arrhythmias, episodic weakness/periodic paralysis, and characteristic dysmorphic features. | Prevalence commonly cited as ~1 per 1,000,000; symptom onset within first 2 decades in 42.3%; ventricular arrhythmias in 60–90%; polymorphic VT 48%; bidirectional VT 44%. | Peer-reviewed review, *Diagnostics* (Nov 2023) (pqac-00000002) | MONDO: Andersen-Tawil syndrome; HPO: Cardiac arrhythmia, Periodic paralysis, Facial dysmorphism |
| Genetics / KCNJ2 / Kir2.1 | ATS1 is caused predominantly by heterozygous loss-of-function variants in **KCNJ2**, encoding inward rectifier potassium channel **Kir2.1**; disease is usually autosomal dominant, with sporadic/de novo cases also reported. | Open Targets disease-target association score 0.8407 for KCNJ2–ATS; 5 supporting evidence items; KCNJ2 mutations account for majority of ATS1 and ~60% of ATS overall in older primary studies. | Database evidence, Open Targets / MONDO_0008222; peer-reviewed primary study, *Circ Cardiovasc Genet* (Feb 2011); review, *Diagnostics* (Nov 2023) (pqac-00000008, pqac-00000004, pqac-00000002) | HGNC: KCNJ2; protein: Kir2.1; GO: inward rectifier potassium channel activity; GO: regulation of membrane potential |
| Variant spectrum | Numerous pathogenic KCNJ2 variants are distributed throughout Kir2.1; dominant-negative effects and trafficking defects are established mechanisms for some variants. | “More than 90 mutations” summarized in 2024 preprint; historical literature cited >40 mutations by 2015 cohort report; example de novo **R260P** showed strong dominant-negative effect. | Preprint, medRxiv (Dec 2024); peer-reviewed cohort, *Muscle & Nerve* (Feb 2015); peer-reviewed primary study, *Circ Cardiovasc Genet* (Feb 2011) (pqac-00000003, pqac-00000009, pqac-00000004) | Sequence variant classes: missense, in-frame deletion; SO terms for missense variant / inframe deletion |
| Cardiac phenotype | Cardiac manifestations include PVCs, ventricular ectopy, prolonged QT/QU intervals with prominent U waves, polymorphic and bidirectional VT, and occasional cardiac arrest/SCD. | In one 15-patient cohort: ventricular arrhythmias 75%, BVT in 6/12 Holters, normal QTc in 76%, prominent U waves in 84%; 37 cardiac arrests in 259-patient meta-analysis. | Peer-reviewed cohort, *Muscle & Nerve* (Feb 2015); peer-reviewed meta-analysis (Jan 2026) (pqac-00000009, pqac-00000010) | HPO: Premature ventricular contractions, Bidirectional ventricular tachycardia, Syncope, Abnormal U wave, Long QT interval |
| Periodic paralysis | Episodic muscle weakness is a core but variably penetrant feature; attacks may be potassium-sensitive and show sex-related variability. | In 15-patient cohort, PP observed in 7 patients across 6 kinships; attacks reported in 20% of females vs 80% of males in that series; females less likely to present with PP in 259-patient meta-analysis (p=0.02). | Peer-reviewed cohort, *Muscle & Nerve* (Feb 2015); peer-reviewed meta-analysis (Jan 2026) (pqac-00000009, pqac-00000010) | HPO: Periodic paralysis, Episodic weakness, Hypokalemia (when present) |
| Dysmorphism | Developmental/craniofacial and limb anomalies are common and aid recognition. | In 15-patient cohort, dysmorphic features noted in 100%; study protocol lists low-set ears, hypertelorism, micrognathia, clinodactyly, syndactyly, hand/foot micromelia as diagnostic features. | Peer-reviewed cohort, *Muscle & Nerve* (Feb 2015); ClinicalTrials.gov observational study description (2007) (pqac-00000009, pqac-00000012) | HPO: Hypertelorism, Micrognathia, Clinodactyly, Syndactyly, Low-set ears |
| Diagnostics | Practical diagnosis relies on recognition of at least 2 of 3 domains: episodic weakness, cardiac conduction/ventricular arrhythmia findings, and dysmorphic features; ECG/Holter and molecular confirmation are key. | Trial protocol diagnostic rule: ≥2 of 3 features; observational natural-history study enrolled 28 participants across 7 sites for standardized longitudinal phenotyping. | ClinicalTrials.gov observational study NCT00521794, completed; supporting clinical review 2023 (pqac-00000012, pqac-00000002) | HPO set above; LOINC/ECG concepts: QTc prolongation, ventricular ectopy; NCIT: genetic testing |
| Mechanism / pathophysiology | Reduced **IK1** from dysfunctional Kir2.1 destabilizes resting membrane potential and repolarization, promoting ventricular ectopy and arrhythmia; some variants also alter sodium current/channelosome behavior. | 2024 preprint reports mutation-specific reductions in IK1 and differential effects on INa with increased ventricular arrhythmia inducibility in multiple mouse models; 2011 R260P study showed trafficking defect with markedly reduced IK1. | Preprint, medRxiv (Dec 2024); peer-reviewed primary study, *Circ Cardiovasc Genet* (Feb 2011); peer-reviewed review, *Naunyn Schmiedebergs Arch Pharmacol* (Apr 2024) (pqac-00000003, pqac-00000004, pqac-00000005) | GO: cardiac muscle cell action potential, membrane repolarization, potassium ion transmembrane transport; CL: cardiomyocyte |
| Treatments / arrhythmia management | Management is individualized; beta-blockers are commonly used, flecainide may reduce arrhythmia burden in some patients, ICD is used in high-risk cases, and class-Ic safety is under active reassessment. | In 15-patient cohort, all arrhythmic patients received beta-blockers and 40% received ICDs; 2024 preprint literature review of 53 ATS1 patients found 54% partial flecainide response, VA reduction in 23%, ineffectiveness in 23%, non-fatal cardiac arrest in 13.5%. | Peer-reviewed cohort, *Muscle & Nerve* (Feb 2015); preprint, medRxiv (Dec 2024) (pqac-00000009, pqac-00000001) | NCIT: Beta-Adrenergic Receptor Blocker Therapy, Flecainide, Implantable Cardioverter-Defibrillator |
| Prognosis / risk | Most patients have chronic morbidity; life-threatening arrhythmias occur in a minority but are clinically important, with sex differences emerging in newer syntheses. | 5-year cumulative SCD probability reported as 7.9%; risk factors summarized in 2023 review include syncope, sustained VT, amiodarone use, micrognathia, periodic paralysis, prolonged Tpeak-Tend; females had higher cardiac arrest risk in 2026 meta-analysis (p=0.02). | Peer-reviewed review, *Diagnostics* (Nov 2023); peer-reviewed meta-analysis (Jan 2026) (pqac-00000002, pqac-00000010) | HPO: Sudden cardiac death, Syncope; prognostic annotation: sustained VT history |
| 2024 hiPSC multi-omics | A 2024 hiPSC-CM disease model combined RNA-seq and ATAC-seq to identify developmental and electrophysiologic ATS mechanisms beyond the primary channel defect. | Mutant iPSC-CMs had lower spontaneous pulsation, prolonged APD, reduced Kir2.1 current; **ZNF528** was continuously downregulated from day 4; 7 potassium-related pathways downregulated (p<0.05); **KCNJ2, CTTN, ATP1B1** were consistently downregulated targets. | Peer-reviewed primary study, *Journal of Translational Medicine* (Mar 2024) (pqac-00000013, pqac-00000014) | GO: potassium ion import/inward rectifier activity pathways; gene entities: ZNF528, CTTN, ATP1B1; CL: induced pluripotent stem cell-derived cardiomyocyte |
| 2024 flecainide precision-safety study | Mutation-specific flecainide safety/efficacy is a major 2024 development; some KCNJ2 variants may confer proarrhythmic risk under class-Ic therapy. | In reviewed 53 ATS1 patients: partial response 54%; VA reduction only 23%; persistent VA in 20–50% of responders; non-fatal cardiac arrest 13.5%; mouse/iPSC models showed increased rotor incidence or inducibility for several variants, while S136F appeared milder. | **Preprint** primary/translational study, medRxiv (Dec 2024) — not peer reviewed at time cited (pqac-00000001, pqac-00000003) | NCIT: Flecainide; variant-level drug response annotation; GO: conduction velocity / arrhythmogenesis |
| Clinical trials | ATS-specific interventional evidence remains sparse; available studies focus on natural history and exploratory therapy. | NCT00521794 observational natural-history study: completed, n=28; NCT00839501 potassium + acetazolamide trial: terminated, phase 1, n=3; NCT06205550 N-of-1 in ATS and MEPPC: not yet recruiting, phase 2, planned n=10. | ClinicalTrials.gov records (2007 onward) (pqac-00000012) | NCIT: Potassium, Acetazolamide; study-design metadata; evidence-source tag: clinical trial registry |


*Table: This table summarizes the most actionable evidence domains for Andersen-Tawil syndrome, including established findings, quantitative support, evidence provenance, and ontology-oriented mapping suggestions. It distinguishes peer-reviewed evidence from the 2024 flecainide preprint and highlights current trial activity.*