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Background: Congenital heart defects (CHD) are among the most frequent manifestations of 22q11.2 deletion syndrome. Although we found relatively few studies aimed at specifically detecting 22q11.2 deletion in newborns (NB) with CHD, none of them has been performed in Mexico. Methods: We conducted a prospective hospital-based study from January 2017 to March 2021 in the Genetics and Pediatric Cardiology Services of the Hospital Civil de Guadalajara Dr. Juan I. Menchaca (Guadalajara, Mexico). All consecutive NBs identified with any non-syndromic major CHD confirmed by echocardiography were eligible to participate. A total of 98 NBs were included, 51 males and 47 females. Fluorescence in situ hybridization (FISH) analysis was conducted to search for deletion of chromosome 22q11.2 in interphase nuclei of standard lymphocyte cultures. Results: We found eight patients (8.2%) with CHD and the 22q11.2 deletion, all of them with conotruncal defects, particularly of the truncus arteriosus (p = 0.013), tetralogy of Fallot (p = 0.024), and pulmonary atresia with ventricular septal defect (p = 0.031) subtypes. With de exception of one infant with hypocalcemia and another with hypocalcemia and thymic aplasia, the diagnosis of 22q11.2 deletion was not clinically suspected in the other patients. Conclusions: Our results confirm the importance of excluding the presence of the 22q11.2 deletion in every NB with CHDs, particularly of the conotruncal subtype, even in the absence of other manifestations.

ABSTRACT Background Retinal dystrophies (RDs) are the most common cause of inherited blindness worldwide and are caused by genetic defects in about 300 different genes. While targeted next‐generation sequencing (NGS) has been demonstrated to be a reliable and efficient method to identify RD disease‐causing variants, it doesn't routinely identify pathogenic structural variant as copy number variations (CNVs). Targeted NGS‐based CNV detection has become a crucial step for RDs molecular diagnosis, particularly in cases without identified causative single nucleotide or Indels variants. Herein, we report the exome sequencing (ES) data‐based read‐depth bioinformatic analysis in a group of 30 unrelated Mexican RD patients with a negative or inconclusive genetic result after ES. Methods CNV detection was performed using ExomeDepth software, an R package designed to detect CNVs using exome data. Bioinformatic validation of identified CNVs was conducted through a commercially available CNV caller. All identified candidate pathogenic CNVs were orthogonally verified through quantitative PCR assays. Results Pathogenic or likely pathogenic CNVs were identified in 6 out of 30 cases (20%), and of them, a definitive molecular diagnosis was reached in 5 cases, for a final diagnostic rate of ~17%. CNV‐carrying genes included CLN3 (2 cases), ABCA4 (novel deletion), EYS, and RPGRIP1. Conclusions Our results indicate that bioinformatic analysis of ES data is a reliable method for pathogenic CNV detection and that it should be incorporated in cases with a negative or inconclusive molecular result after ES.