When to test fetuses for RASopathies? Proposition from a systematic analysis of 352 multicenter cases and a postnatal cohort.

PURPOSE: Recent studies have identified suggestive prenatal features of RASopathies (e.g., increased nuchal translucency [NT], cystic hygroma [CH], hydrops, effusions, congenital heart diseases [CHD], polyhydramnios, renal anomalies). Our objective is to clarify indications for RASopathy prenatal testing. We compare genotype distributions between pre- and postnatal populations and propose genotype-phenotype correlations. METHODS: Three hundred fifty-two chromosomal microarray-negative cases sent for prenatal RASopathy testing between 2012 and 2019 were collected. For most, 11 RASopathy genes were tested. Postnatal cohorts (25 patients with available prenatal information and 108 institutional database genotypes) and the NSeuroNet database were used for genotypic comparisons. RESULTS: The overall diagnostic yield was 14% (50/352), with rates >20% for effusions, hydrops, and CHD. Diagnostic yield was significantly improved in presence of hypertrophic cardiomyopathy (HCM), persistent or associated CH, any suggestive finding combined with renal anomaly or polyhydramnios, or ≥2 ultrasound findings. Largest prenatal contributors of pathogenic variants were PTPN11 (30%), RIT1 (16%), RAF1 (14%), and HRAS (12%), which considerably differ from their prevalence in postnatal populations. HRAS, LZTR1, and RAF1 variants correlated with hydrops/effusions, and RIT1 with prenatal onset HCM. CONCLUSION: After normal chromosomal microarray, RASopathies should be considered when any ultrasound finding of lymphatic dysplasia or suggestive CHD is found alone or in association.

A mutation update on the LDS-associated genes TGFB2/3 and SMAD2/3.

The Loeys-Dietz syndrome (LDS) is a connective tissue disorder affecting the cardiovascular, skeletal, and ocular system. Most typically, LDS patients present with aortic aneurysms and arterial tortuosity, hypertelorism, and bifid/broad uvula or cleft palate. Initially, mutations in transforming growth factor-ß (TGF-ß) receptors (TGFBR1 and TGFBR2) were described to cause LDS, hereby leading to impaired TGF-ß signaling. More recently, TGF-ß ligands, TGFB2 and TGFB3, as well as intracellular downstream effectors of the TGF-ß pathway, SMAD2 and SMAD3, were shown to be involved in LDS. This emphasizes the role of disturbed TGF-ß signaling in LDS pathogenesis. Since most literature so far has focused on TGFBR1/2, we provide a comprehensive review on the known and some novel TGFB2/3 and SMAD2/3 mutations. For TGFB2 and SMAD3, the clinical manifestations, both of the patients previously described in the literature and our newly reported patients, are summarized in detail. This clearly indicates that LDS concerns a disorder with a broad phenotypical spectrum that is still emerging as more patients will be identified. All mutations described here are present in the corresponding Leiden Open Variant Database.

Search for genetic factors in bicuspid aortic valve disease: ACTA2 mutations do not play a major role.

OBJECTIVES: Mutations in ACTA2 have been reported as a cause of familiar thoracic aortic aneurysm (TAA) with associated bicuspid aortic valve (BAV) in some individuals. Our aim is to investigate the role of ACTA2 mutations in BAV associated with TAA in 20 patients. METHODS: We recruited 20 patients who underwent surgery for BAV and TAA; clinical genetic evaluation and ACTA2 mutation analysis were performed on each patient, along with next-generation sequencing analysis of BAV-related genes. Available first-degree relatives were enrolled and evaluated with echocardiography and clinical genetic examination. RESULTS: No mutations were found in ACTA2 or in BAV-related genes in our probands nor any common clinical signs possibly related to their heart disease. One-third of probands did not have any cardiovascular risk factor. Surgery was required at a young age (mean age 47.2 years) and at relatively small ascending aortic diameters (mean size 49.7 mm). In 77 first-degree relatives, 1 new diagnosis of TAA requiring surgery was made and 8 previous BAV/TAA diagnoses (9/77 = 11.7%) were confirmed. The phenotype BAV ± TAA segregated in 25% of our families. CONCLUSIONS: Although based on a small cohort, our results seemed to justify the conclusion that ACTA2 did not play a significant role in the pathogenesis of BAV aortopathy. The underlying genetic factors of this condition remain elusive and both large association studies and exome or genome sequencing could represent promising tools to unravel its pathogenesis. Aortic resection of TAA at elective surgery in these patients should be recommended as well as echocardiography in their first-degree relatives.