Novel presentation of CACNA1C variant as neonatal complete atrioventricular block, heart failure and non-compaction cardiomyopathy with oligogenic influences.

Pathogenic CACNA1C variants are associated with long QT syndrome, cardiac conduction disorders (CCD), short QT or Brugada syndromes, sudden cardiac death, and rarely hypertrophic cardiomyopathy. Neonatal complete AV block (CAVB) has not been previously reported in patients with CACNA1C-mutations. We present a neonate with CAVB, severe heart failure, and non-compaction cardiomyopathy, found to have a de novo, likely pathogenic, heterozygous CACNA1C variant and heterozygous variants of uncertain significance (VUS) in TNNI3K, GATA6, and PDHK1 genes. This case expands the CACNA1C-associated phenotype to include neonatal CAVB and suggests a potential oligogenic contribution to severe neonatal cardiac disease.