The Trace of c. 3747₃748insGG Variation of the MYBPC3 Gene in the Family With Atrioventricular Canal Defect

Background Atrioventricular canal defect (AVCD) is a congenital heart disease often associated with genetic changes, with a broad spectrum of anatomical patterns. Aim We present a novel likely pathogenic variant of MYBPC3 in a proband with AVCD. Methods A clinical and genetic evaluation was conducted on a one‐year‐old Iranian girl referred to our center with cardiac structural abnormalities and her family. Transthoracic echocardiography (TTE) and cardiac computed tomography (CT) were employed for clinical evaluation, and whole exome sequencing (WES), polymerase chain reaction (PCR), and Sanger sequencing were utilized for genetic analysis. Results TTE revealed a ventricular and atrial septal defect (ASD), along with pulmonary hypertension (PH). The proband was diagnosed with AVCD through cardiac CT. WES identified a novel heterozygous MYBPC3 (NM₀00256. 3): c. 3747₃748insGG; p. (Ile1250Glyfs∗82). Segregation analysis confirmed the presence of the same variant in the proband’s father, who was diagnosed with hypertrophic cardiomyopathy (HCM). Conclusion We presented the first case of AVCD associated with a novel MYBPC3 variant, expanding the spectrum of cardiac anomalies linked to MYBPC3 mutations. The findings highlight the complexity and variable expression of MYBPC3 within affected family members.