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Repurposing anticancer drugs to vascular malformations has significantly improved patient outcomes. Complex Lymphatic Anomalies (CLA) are part of the spectrum of lymphatic malformations (LMs) that share similar oncogenic mutations to cancer. We report the case of a young patient with highly symptomatic CLA who was initially treated with sirolimus, due to the frequent involvement of the PI3K-AKT-mTOR pathway in CLA pathogenesis. Despite an initial reduction in symptoms, sirolimus progressively lost its effectiveness. After an unsuccessful attempt with trametinib alone, sirolimus was added to trametinib and resulted in a significant, rapid and sustained improvement in symptoms. This suggests that, contrary to current dogmas, combination therapy using sub-therapeutic doses targeting both the PI3K and RAS pathways retains efficacy without generating the toxicity known for combination therapies, and is beneficial in the management of CLAs and potentially other vascular anomalies.

Primary lymphedema (PL), characterized by tissue swelling, fat accumulation, and fibrosis, results from defects in lymphatic vessels or valves caused by mutations in genes involved in development, maturation, and function of the lymphatic vascular system. Pathogenic variants in various genes have been identified in about 30% of PL cases. By screening of a cohort of 755 individuals with PL, we identified two TIE1 (tyrosine kinase with immunoglobulin- and epidermal growth factor-like domains 1) missense variants and one truncating variant, all predicted to be pathogenic by bioinformatic algorithms. The TIE1 receptor, in complex with TIE2, binds angiopoietins to regulate the formation and remodeling of blood and lymphatic vessels. The premature stop codon mutant encoded an inactive truncated extracellular TIE1 fragment with decreased mRNA stability, and the amino acid substitutions led to decreased TIE1 signaling activity. By reproducing the two missense variants in mouse Tie1 via CRISPR/Cas9, we showed that both cause edema and are lethal in homozygous mice. Thus, our results indicate that TIE1 loss-of-function variants can cause lymphatic dysfunction in patients. Together with our earlier demonstration that ANGPT2 loss-of-function mutations can also cause PL, our results emphasize the important role of the ANGPT2/TIE1 pathway in lymphatic function.

BACKGROUNDSlow-flow vascular malformations frequently harbor activating mutations in the PI3K/AKT/mTOR cascade. Phase II trials pinpointed sirolimus effectiveness as a drug therapy. Efficacy and safety of sirolimus thus need to be evaluated in large prospective phase III trials.METHODSThe Vascular Anomaly-Sirolimus-Europe (VASE) trial, initiated in 2016, is a large multicentric prospective phase III trial (EudraCT 2015-001703-32), which evaluates efficacy and safety of sirolimus for 2 years in pediatric and adult patients with symptomatic slow-flow vascular malformations. In this interim analysis, we studied all patients enrolled up to October 2021 who received sirolimus for 12 or more months or who prematurely stopped the treatment.RESULTSThirty-one pediatric and 101 adult patients were included in this analysis; 107 completed 12 or more months of sirolimus, including 61 who were treated for the whole 2-year period. Sirolimus resulted in a clinical improvement in 85% of patients. The efficacy appeared within the first month for the majority of them. Grade 3-4 adverse events were observed in 24 (18%) patients; all resolved after treatment interruption/arrest. Sirolimus increased feasibility of surgery or sclerotherapy in 20 (15%) patients initially deemed unsuitable for intervention. Among the 61 patients who completed the 2-year treatment, 33 (54%) reported a recurrence of symptoms after a median follow-up of 13 months after sirolimus arrest. While there was no difference in efficacy, clinical improvement was faster but subsided more rapidly in PIK3CA-mutated (n = 24) compared with TIE2-mutated (n = 19) patients.CONCLUSIONSirolimus has a high efficacy and good tolerance in treatment of slow-flow vascular malformations in children and adults.TRIAL REGISTRATIONClinicalTrials.gov NCT02638389 and EudraCT 2015-001703-32.FUNDINGThe Fonds de la Recherche Scientifique (FNRS grants T.0247.19, P.C005.22, T.0146.16, and P.C013.20), the Fund Generet managed by the King Baudouin Foundation (grant 2018-J1810250-211305), the Walloon Region through the FRFS-WELBIO strategic research programme (WELBIO-CR-2019C-06), the MSCA-ITN network V.A. Cure no. 814316, the Leducq Foundation Networks of Excellence Program grant \"ReVAMP\" (LFCR grant 21CVD03), the European Union's Horizon 2020 research and innovation programme under grant agreement no. 874708 (Theralymph), the Swiss National Science Foundation under the Sinergia project no. CRSII5_193694, and a Pierre M. fellowship.

Background Vascular anomalies caused by somatic (postzygotic) variants are clinically and genetically heterogeneous diseases with overlapping or distinct entities. The genetic knowledge in this field is rapidly growing, and genetic testing is now part of the diagnostic workup alongside the clinical, radiological and histopathological data. Nonetheless, access to genetic testing is still limited, and there is significant heterogeneity across the approaches used by the diagnostic laboratories, with direct consequences on test sensitivity and accuracy. The clinical utility of genetic testing is expected to increase progressively with improved theragnostics, which will be based on information about the efficacy and safety of the emerging drugs and future molecules. The aim of this study was to make recommendations for optimising and guiding the diagnostic genetic testing for somatic variants in patients with vascular malformations. Results Physicians and lab specialists from 11 multidisciplinary European centres for vascular anomalies reviewed the genes identified to date as being involved in non-hereditary vascular malformations, evaluated gene–disease associations, and made recommendations about the technical aspects for identification of low-level mosaicism and variant interpretation. A core list of 24 genes were selected based on the current practices in the participating laboratories, the ISSVA classification and the literature. In total 45 gene–phenotype associations were evaluated: 16 were considered definitive, 16 strong, 3 moderate, 7 limited and 3 with no evidence. Conclusions This work provides a detailed evidence-based view of the gene–disease associations in the field of vascular malformations caused by somatic variants. Knowing both the gene–phenotype relationships and the strength of the associations greatly help laboratories in data interpretation and eventually in the clinical diagnosis. This study reflects the state of knowledge as of mid-2023 and will be regularly updated on the VASCERN-VASCA website (VASCERN-VASCA, https://vascern.eu/groupe/vascular-anomalies/ ).

Joris Veltman and colleagues apply exome sequencing to identify heterozygous de novo mutations in SETBP1 as the cause of Schinzel-Giedion syndrome, a rare sporadic disorder characterized by severe intellectual disability and multiple congenital malformations. Schinzel-Giedion syndrome is characterized by severe mental retardation, distinctive facial features and multiple congenital malformations; most affected individuals die before the age of ten. We sequenced the exomes of four affected individuals (cases) and found heterozygous de novo variants in SETBP1 in all four. We also identified SETBP1 mutations in eight additional cases using Sanger sequencing. All mutations clustered to a highly conserved 11-bp exonic region, suggesting a dominant-negative or gain-of-function effect.

Background Congenital hydrocephalus is characterized by ventriculomegaly, defined as a dilatation of cerebral ventricles, and thought to be due to impaired cerebrospinal fluid (CSF) homeostasis. Primary congenital hydrocephalus is a subset of cases with prenatal onset and absence of another primary cause, e.g., brain hemorrhage. Published series report a Mendelian cause in only a minority of cases. In this study, we analyzed exome data of PCH patients in search of novel causal genes and addressed the possibility of an underlying oligogenic mode of inheritance for PCH. Materials and methods We sequenced the exome in 28 unrelated probands with PCH, 12 of whom from families with at least two affected siblings and 9 of whom consanguineous, thereby increasing the contribution of genetic causes. Patient exome data were first analyzed for rare (MAF < 0.005) transmitted or de novo variants. Population stratification of unrelated PCH patients and controls was determined by principle component analysis, and outliers identified using Mahalanobis distance 5% as cutoff. Patient and control exome data for genes biologically related to cilia (SYScilia database) were analyzed by mutation burden test. Results In 18% of probands, we identify a causal (pathogenic or likely pathogenic) variant of a known hydrocephalus gene, including genes for postnatal, syndromic hydrocephalus, not previously reported in isolated PCH. In a further 11%, we identify mutations in novel candidate genes. Through mutation burden tests, we demonstrate a significant burden of genetic variants in genes coding for proteins of the primary cilium in PCH patients compared to controls. Conclusion Our study confirms the low contribution of Mendelian mutations in PCH and reports PCH as a phenotypic presentation of some known genes known for syndromic, postnatal hydrocephalus. Furthermore, this study identifies novel Mendelian candidate genes, and provides evidence for oligogenic inheritance implicating primary cilia in PCH.

Background Venous malformations (VMs) are the most common vascular anomalies and have been associated with somatic variants in TEK. Current treatment of VM joint component might be challenging due to the size or location of some lesions or ineffective with recurrence of malformed veins. Targeted molecular therapies after identification of genetic defects might be an alternative. Methods We report a case with intraarticular bleeding due to VM with a TEK pathogenic somatic variant treated with rapamycin. Results A 26‐year‐old female patient was evaluated for right calf pain secondary to venous malformation of the right inferior limb with an intraarticular component in the right knee. Hemarthrosis and degenerative chondropathy of the knee were evidenced at MRA. Molecular diagnosis evidenced a pathogenic somatic TEK variant. Rapamycin was introduced to stop bleeding, with good tolerance and efficacy. Conclusion The TEK receptor signals through the PI3K/AKT/mTOR pathway and TEK mutations have been linked to AKT activation. As rapamycin acts against angiogenesis and reduces phosphorylated‐AKT levels, targeted molecular therapy should be discussed as first‐line therapy in patients with proven molecular diagnosis and diffuse VM inaccessible to conventional treatment. Treatment of intraarticular vascular malformation can be challenging. In this case report, TEK‐related intraarticular venous malformation leading to intraarticular bleeding with hemarthrosis and degenerative chondropathy was successfully treated by rapamycin.

The genetic basis of nonsyndromic orofacial cleft (NsOFC) remains elusive, although associations have been identified with various genetic loci. NsOFC has a less pronounced genetic background than syndromic orofacial cleft (SyOFC), albeit Mendelian inheritance has been identified. Our hypothesis was that genes related to spliceosome function may contribute to NsOFC pathophysiology, as they do for some syndromic cases. Exome sequencing was conducted on 224 unrelated NsOFC probands. We performed filtering and analyses of predicted pathogenicity of rare variants using Highlander. We focused on 26 genes encoding spliceosome proteins. Subsequently, bioinformatic tools, such as AlphaFold, and PyMol, were applied to generate three‐dimensional structures to interpret the effects of the identified variants on protein structure and interaction domains. We found six likely damaging variants: three heterozygous missense variants in small nuclear ribonucleoprotein U5 200 kDa subunit ( SNRNP200 ) in three multiplex NsOFC families, and two missense and one splice site variant in splicing factor 3b subunit 1 ( SF3B1 ), 4 ( SF3B4 ), and 2 ( SF3B2 ) in two posterior CP families and a complete CP patient, respectively. These results suggest that variants in the spliceosome complex genes, observed in 2.7% of NsOFC cases in our cohort, may contribute to disease susceptibility as potential risk factors.