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Deleterious variants in collagen genes are the most common cause of hereditary connective tissue disorders (HCTD). Adaptations of the American College of Medical Genetics and Genomics/Association for Molecular Pathology (ACMG/AMP) criteria are still lacking. A multidisciplinary team was set up for developing specifications of the ACMG/AMP criteria for COL1A1, COL1A2, COL2A1, COL3A1, COL5A1, COL5A2, COL11A1, COL11A2 and COL12A1, associated with various forms of HCTD featuring joint hypermobility, which is becoming one of the most common reasons of referral for molecular testing in this field. Such specifications were validated against 209 variants, and resulted effective for classifying as pathogenic and likely pathogenic null alleles without downgrading of the PVS1 level of strength and recurrent Glycine substitutions. Adaptations of selected criteria reduced uncertainties on private Glycine substitutions, intronic variants predicted to affect the splicing, and null alleles with a downgraded PVS1 level of strength. Segregation and multigene panel sequencing data mitigated uncertainties on non-Glycine substitutions by the attribution of one or more benignity criteria. These specifications may improve the clinical utility of molecular testing in HCTD by reducing the number of variants with neutral/conflicting interpretations. Close interactions between laboratory and clinicians are crucial to estimate the a priori utility of molecular test and to improve medical reports. [ABSTRACT FROM AUTHOR]

The 22q11.2 microdeletion syndrome (22q11.2 DGS) is characterized by an extreme intrafamilial and interfamilial variability. The main clinical features are congenital heart defects, palatal abnormalities, learning disability, facial dysmorphisms and immune deficiency. In 85–90% of cases, the 22q11.2 DGS is caused by a heterozygous ~3-Mb deletion, including the TBX1 gene, considered one of the major genes responsible for heart defects. Individuals with atypical deletions with at least one breakpoint outside low copy repeats have been reported. Our patient is a child presenting tetralogy of Fallot (TOF) with an atypical 22q11.2 deletion proximal to the critical DiGeorge region. The rearrangement was inherited from the healthy mother and spanned ~642–970 kb, encompassing DGCR6 and PRODH, two novel possible candidate genes for conotruncal heart defects. [ABSTRACT FROM AUTHOR]