Brugada Syndrome

About this condition

Brugada Syndrome (BrS) is a cardiac channelopathy characterized by a distinctive ECG pattern — ST-segment elevation in right precordial leads (V1–V3) — and a markedly elevated risk of ventricular fibrillation and sudden cardiac death, particularly during rest, sleep, or fever. Prevalence is estimated at 1–5 per 10,000 worldwide, with significantly higher prevalence in Southeast Asian populations (up to 1 in 1,000). BrS predominantly affects males (8:1 ratio), with mean age of sudden death around 40 years. The condition follows autosomal dominant inheritance but shows extremely incomplete penetrance — many individuals with pathogenic variants never experience arrhythmias or may develop symptoms only later in life.

SCN5A, which encodes the cardiac sodium channel Nav1.5, is the primary gene implicated in BrS, found in approximately 20–25% of patients. Unlike in Long QT Syndrome Type 3 (where SCN5A gain-of-function variants prolong the QT interval), BrS is caused by loss-of-function variants that reduce sodium current, creating a transmural voltage gradient in the right ventricular outflow tract. This abnormality is invisible on most ECGs — the BrS-type ECG pattern appears intermittently, sometimes only after fever or during sleep. Approximately 65–75% of BrS patients have no identifiable pathogenic variant in any known BrS gene, suggesting undiscovered genetic mechanisms.

Confirming a Brugada syndrome diagnosis has immediate therapeutic implications. Patients with high-risk features — prior syncope or cardiac arrest, fever-triggered symptoms, or family history of sudden death — are candidates for implantable cardioverter-defibrillator (ICD) placement, which prevents sudden death by detecting and terminating life-threatening arrhythmias. Identifying a pathogenic variant enables cascade testing of family members, though the variable expressivity means many carriers may remain asymptomatic. Genetic counseling addresses avoidance of drugs known to unmask the BrS-type ECG pattern (certain antiarrhythmics, antibiotics, antihistamines), fever management, and family planning. For high-risk carriers, an ICD is a genuinely life-saving intervention.

Only 20–25% of clinically diagnosed Brugada Syndrome patients harbor SCN5A mutations; the remaining majority remains genetically unexplained, suggesting substantial genetic heterogeneity or polygenic contributors.

Gene locus: SCN5A (3p22.2)

Only 20–25% of Brugada Syndrome patients have identifiable SCN5A variants. The majority remain genetically unresolved — panels alone cannot capture the missing heritability.

Two-thirds of Brugada patients lack a genetic diagnosis

Only approximately 20–25% of clinically diagnosed Brugada Syndrome patients have an identifiable pathogenic variant in SCN5A, and only 30–35% have any molecular finding in any known BrS gene. This leaves 65–70% of patients genetically unresolved. Standard BrS panels screen SCN5A and sometimes candidate genes, but the vast majority of genetic variance in BrS remains unexplained. Whole genome sequencing enables both rare variant detection across all genes and the calculation of genome-wide polygenic risk scores, which may eventually explain some of the missing heritability in BrS.

A finding identifies at-risk family members for preventive ICD placement

When an SCN5A variant is confirmed, it enables cascade testing of family members — identifying at-risk relatives who may carry the same mutation without ECG abnormalities (since the BrS pattern is frequently intermittent). For carriers with high-risk features (prior syncope, fever-triggered arrhythmias, family history of sudden death), ICD placement is a genuinely life-saving intervention. Genetic information informs counseling about drug interactions (avoiding medications that unmask the BrS-type ECG pattern), fever management, and activity modification. For asymptomatic carriers with normal screening, periodic reassessment is appropriate.

A normal ECG at rest. No symptoms anyone noticed. And a cardiac rhythm disorder that only reveals itself under specific conditions — unless you look at the gene first.