A +3 variant at a donor splice site leads to a skipping of the MYH11 exon 32, a recurrent RNA defect causing Heritable Thoracic Aortic Aneurysm and Dissection and/or Patent Ductus Arteriosus

Abstract Background Pathogenic variants in MYH11 are associated with either heritable thoracic aortic aneurysm and dissection (HTAAD), patent ductus arteriosus (PDA) syndrome, or megacystis‐microcolon‐intestinal hypoperistalsis syndrome (MMIHS). Methods and Results We report a family referred for molecular diagnosis with HTAAD/PDA phenotype in which we found a variant at a non‐conserved position of the 5’ donor splice site of intron 32 of MYH11 potentially altering splicing (NM_002474.3:c.4578+3A>C). Although its cosegregation with disease was observed, it remained of unknown significance. Later, aortic surgery in the proband gave us the opportunity to perform a transcript analysis. This showed a skipping of the exon 32, an RNA defect previously reported to be translated to an in‐frame loss of 71 amino acids and a dominant‐negative effect in the smooth muscle myosin rod. This RNA defect is also reported in 3 other HTAAD/PDA pedigrees. Conclusion This report confirms that among rare variants in MYH11, skipping of exon 32 is recurrent. This finding is of particular interest to establish complex genotype–phenotype correlations where some alleles are associated with autosomal dominant HTAAD/PDA, while others result in recessive or dominant visceral myopathies.