Megacystis‐microcolon‐intestinal‐hypoperistalsis syndrome (MMIHS) is a severe congenital visceral myopathy characterized by an abdominal distension due to a large non‐obstructed urinary bladder, a microcolon and intestinal hypo‐ or aperistalsis. Most of the patients described to date carry a sporadic heterozygous variant in ACTG2. More recently, recessive forms have been reported and mutations in MYH11, LMOD1, MYLK and MYL9 have been described at the molecular level. In the present report, we describe five patients carrying a recurrent heterozygous variant in ACTG2. Exome sequencing performed in four families allowed us to identify the genetic cause in three. In two families, we identified variants in MMIHS causal genes, respectively a nonsense homozygous variant in MYH11 and a previously described homozygous deletion in MYL9. Finally, we identified compound heterozygous variants in a novel candidate gene, PDCL3, c.[143_144del];[380G>A], p.[(Tyr48Ter)];[(Cys127Tyr)]. After cDNA analysis, a complete absence of PDLC3 expression was observed in affected individuals, indicating that both mutated transcripts were unstable and prone to mediated mRNA decay. PDCL3 encodes a protein involved in the folding of actin, a key step in thin filament formation. Presumably, loss‐of‐function of this protein affects the contractility of smooth muscle tissues, making PDCL3 an excellent candidate gene for autosomal recessive forms of MMIHS.

Objectives The antenatal phenotypic spectrum of Noonan Syndrome (NS) requires better characterization. Methods This multicenter retrospective observational included 16 fetuses with molecularly confirmed NS admitted for fetopathological examination between 2009 and 2016. Results Among 12 pathogenic variants (PV) in PTPN11 (80%), 5 (42%) fell between position c.179 and c.182. Ultrasound showed increased nuchal translucency (n = 13/16, 93%), increased nuchal fold after 15 weeks of gestation (n = 12/16, 75%), pleural effusions (n = 11/16, 69%), polyhydramnios (n = 9/16, 56%), hydrops (n = 7/16, 44%), cardiovascular (n = 6/16, 38%) and cerebral (n = 4/16, 25%) anomalies. Fetopathological examination found dysmorphic features in all cases, cardiovascular anomalies (n = 12/15, 80%), pulmonary hypoplasia (n = 10/15, 67%), effusions (n = 7/15, 47%) and neuropathological anomalies (n = 5/15, 33%). Hydrops was significantly (p = 0.02) more frequent in the four fetuses with RIT1, NRAS and RAF1 PV versus the 12 fetuses with PTPN11 PV. Conclusions Increased nuchal translucency and nuchal fold is common in NS. Noonan Syndrome antenatal phenotype showed high in utero fetal death, hydrops, prenatal pleural effusion and pulmonary hypoplasia, although the inclusion of only deceased fetuses will have selected more severe phenotypes. Non‐specific cardiovascular and neurological abnormalities should be added to NS antenatal phenotype. Next generation sequencing will help detect more genotypes, clarifying the prenatal phenotype and identifying genotype‐phenotype correlations.

Infantile hemangioma (IH) is the most common benign vascular tumor of infancy, occurring predominantly in the head and neck. It is characterized by specific endothelial expression of glucose transporter-1 (GLUT-1) and involution with time, spontaneous or on beta-blockers treatment. Although some predisposing factors are known, the exact pathogenesis remains unclear. We report a case of pulmonary IH GLUT-1 positive, initially suspected as a cystic pulmonary airway malformation, in a child presenting with both cardiac and renal malformations. The clinical, radiological, pathological, and genetics findings are discussed with a review of the literature. Although pulmonary IH is a rare lesion, it should be suspected when facing a pulmonary cystic mass in a child.

Short oral presentation abstracts OP02.05The nasofrontal angle can help to identify palate involvement in fetuses with facial clefts