BabyScreen+ newborn screening

Gene: CALM3

Green List (high evidence)

Variants in this gene also cause Long QT syndrome, and other Long QT syndrome genes have been included in the panel.

Created: 1 Feb 2023, 7:10 a.m. | Last Modified: 1 Feb 2023, 7:10 a.m.

Panel Version: 0.1849

Rated as 'strong actionability' for paediatric patients by ClinGen.

The mean age of onset of symptoms (usually a syncopal episode) of CPVT is between age seven and twelve years; onset as late as the fourth decade of life has been reported. Nearly 60% of patients have at least one syncopal episode before age 40. If untreated, CPVT is highly lethal, as approximately 30% of genetically affected individuals experience at least one cardiac arrest and up to 80% one or more syncopal spells. In untreated patients, the 8-year fatal or near-fatal event rates of 25% have been reported. Sudden death may be the first manifestation of the disease. Instances of sudden infant death syndrome (SIDS) have been associated with pathogenic variants in RYR2.

Individuals with pathogenic variants in CALM1, CALM2 or CALM3 can have a severe phenotype, with earlier onset, QT prolongation, and a high predilection for cardiac arrest and sudden death.

Beta-blockers lacking intrinsic sympathomimetic activity are recommended as a first-line therapy in all patients with a clinical diagnosis of CPVT, including those with documented spontaneous, stress-induced VAs. Guidelines differ in their recommendations about utilizing beta-blocker therapy in phenotype negative individuals. Treatment with beta blockers is associated with a reduction in adverse cardiac events. However, variability in outcome with beta-blocker therapy is due to multiple factors, including dosing and compliance. In a study of 101 patients with CPVT (22 diagnosed clinically and 79 diagnosed molecularly), 81 were administered beta-blockers (57 symptomatic and 24 asymptomatic individuals). Estimated 4- and 8-year cardiac event rates were 8% and 27%, respectively in patients taking beta-blockers, and 33% and 58% in those not taking beta blockers (log-rank p=0.01). Corresponding statistics for fatal events were 1% and 11% with beta-blockers vs. 18% and 25% without (log-rank p=0.05). Event rates in asymptomatic patients with a positive genotype were similar to other patients. In multivariate models, absence of beta-blockers was an independent predictor of cardiac events (hazard ratio [HR], 5.48; 95% CI, 1.8 to 16.7, p=0.003) and of fatal events (HR, 5.54; 95% CI, 1.2 to 26.1, p=0.03). Of the 37 asymptomatic patients with a positive genotype, 9 (24%) had cardiac events.

In patients with CPVT and recurrent sustained VT or syncope, while receiving adequate or maximally tolerated beta blocker, treatment intensification with either combination medication therapy (e.g., beta blocker with flecainide), left cardiac sympathetic denervation, and/or an ICD is recommended.

Clinical penetrance ranges from 25 to 100%, with an average of 70 to 80%. Syncope appears to be the first symptom in more than half of the patients. When untreated, mortality from CPVT is high, reaching 30 to 50% by the age of 30 years.

Exclude for CPVT: association has moderate evidence, there are issues with penetrance, and treatment is generally only recommended in symptomatic individuals.
Sources: ClinGen

Created: 29 Dec 2022, 8:35 a.m. | Last Modified: 29 Mar 2023, 12:58 a.m.

Panel Version: 0.2124

Mode of inheritance
MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted

Phenotypes
Long QT syndrome 16, MIM#618782