Loeys-Dietz Syndrome Panel

Loeys-Dietz syndrome (LDS) is characterized by two major clinical features: vascular findings (cerebral, thoracic, and abdominal arterial aneurysms and/or dissections) and skeletal manifestations (pectus excavatum or pectus carinatum, scoliosis, joint laxity, arachnodactyly, talipes equinovarus). Additional variable features include craniofacial abnormalities (ocular hypertelorism, bifid uvula/cleft palate and craniosynostosis) and cutaneous findings (translucent skin, easy bruising and dystrophic scars) (Loeys et al. 2005. PubMed ID: 15731757). Two clinical entities of LDS have been described (types 1 and 2), which represent a continuum of clinical features. Approximately 75% of patients with LDS type 1 have craniofacial manifestations, while approximately 25% of patients with LDS type 2 have cutaneous manifestations (Loeys et al. 2005. PubMed ID: 15731757; Loeys et al. 2006. PubMed ID: 16928994). LDS is usually characterized by aggressive arterial aneurysms (mean age at death 26.1 years) and high incidence of pregnancy-related complications including death and uterine rupture (Loeys et al. 2005. PubMed ID: 15731757). Clinical features of LDS overlap with Marfan syndrome (Loeys et al. 2005. PubMed ID: 15731757; Loeys and Dietz. 2013. PubMed ID: 20301312).

LDS is inherited in an autosomal dominant manner due to pathogenic variants in TGFBR1, TGFBR2, SMAD3, TGFB2, and TGFB3 (Loeys et al. 2005. PubMed ID: 15731757; Mizuguchi et al. 2004. PubMed ID: 15235604; Rienhoff et al. 2013. PubMed ID: 23824657). TGFBR1, TGFBR2, SMAD3, and TGFB2 are all involved in TGFβ signaling. TGFB2 is a cytokine, TGFBR1 and TGFBR2 are receptors and SMAD3 is a signal transducer and transcription factor. The majority of documented causative variants in TGFBR1, TGFBR2, and SMAD3 are missense (Loeys et al. 2005. PubMed ID: 15731757; Loeys et al. 2006. PubMed ID: 16928994; Stheneur et al. 2008. PubMed ID: 18781618; Lerner-Ellis et al. 2014. PubMed ID: 24793577). A combination of truncating variants (nonsense, frameshifts) and missense variants have been found in TGFB2 and TGFB3 (Lindsay et al. 2012. PubMed ID: 22772368, Boileau et al. 2012. PubMed ID: 22772371; Rienhoff et al. 2013. PubMed ID: 23824657; Schepers et al. 2018. PubMed ID: 29392890). Individuals who harbor a SMAD3 pathogenic variant are at an increased risk for osteoarthritis (van de Laar et al. 2011. PubMed ID: 21217753; van de Laar et al. 2012. PubMed ID: 22167769). Approximately 25% of cases are familial and 75% of cases are de novo (Loeys and Dietz. 2013. PubMed ID: 20301312).

Approximately 95% of Loeys-Dietz cases are found to have a pathogenic variant in TGFBR1, TGFBR2, SMAD3, TGFB2, or TGFB3 (Loeys and Dietz. 2013. PubMed ID: 20301312).

This test is performed using Next-Gen sequencing with additional Sanger sequencing as necessary.

This panel typically provides 100% coverage of all coding exons of the genes plus 10 bases of flanking noncoding DNA in all available transcripts along with other non-coding regions in which pathogenic variants have been identified at PreventionGenetics or reported elsewhere. We define coverage as ≥20X NGS reads or Sanger sequencing. PGnome panels typically provide slightly increased coverage over the PGxome equivalent. PGnome sequencing panels have the added benefit of additional analysis and reporting of deep intronic regions (where applicable).

Dependent on the sequencing backbone selected for this testing, discounted reflex testing to any other similar backbone-based test is available (i.e., PGxome panel to whole PGxome; PGnome panel to whole PGnome).