Clinical delineation and natural history of the PIK3CA-related overgrowth spectrum

PIK3CA mutations enhance the adipogenesis of ADSCs in facial infiltrating lipomatosis through TRPV1

Facial infiltrating lipomatosis (FIL) is a congenital disorder. The pathogenesis of FIL is associated with PIK3CA mutations, but the underlying mechanisms remain undetermined. We found that the adipose tissue in FIL demonstrated adipocytes hypertrophy and increased lipid accumulation. All adipose-derived mesenchymal stem cells from FIL (FIL-ADSCs) harbored PIK3CA mutations. Moreover, FIL-ADSCs exhibited a greater capacity for adipogenesis. Knockdown of PIK3CA resulted in a reduction in the adipogenic potential of FIL-ADSCs. Furthermore, WX390, a dual-target PI3K/mTOR inhibitor, was found to impede PIK3CA-mediated adipogenesis both in vivo and in vitro. RNA sequencing (RNA-seq) revealed that the expression of transient receptor potential vanilloid subtype 1 (TRPV1) was upregulated after PI3K pathway inhibition, and overexpression or activation of TRPV1 both inhibited adipogenesis. Our study showed that PIK3CA mutations promoted adipogenesis in FIL-ADSCs and this effect was achieved by suppressing TPRV1. Pathogenesis experiments suggested that WX390 may serve as an agent for the treatment of FIL.

Pharmacogenetics in Oncology: A useful tool for individualizing drug therapy

With the continuous development of genetics in healthcare, there has been a significant contribution to the development of precision medicine, which is ultimately aimed at improving the care of patients. Generally, drug treatments used in Oncology are characterized by a narrow therapeutic range and by their potential toxicity. Knowledge of pharmacogenomics and pharmacogenetics can be very useful in the area of Oncology, as they constitute additional tools that can help to individualize patients' treatment. This work includes a description of some genes that have been revealed to be useful in the field of Oncology, as they play a role in drug prescription and in the prediction of treatment response.

Genetic mutations and phenotype characteristics in peripheral vascular malformations: A systematic review

Vascular malformations (VMs) are clinically diverse with regard to the vessel type, anatomical location, tissue involvement and size. Consequently, symptoms and disease impact differ significantly. Diverse causative mutations in more and more genes are discovered and play a major role in the development of VMs. However, the relationship between the underlying causative mutations and the highly variable phenotype of VMs is not yet fully understood. In this systematic review, we aimed to provide an overview of known causative mutations in genes in VMs and discuss associations between the causative mutations and clinical phenotypes. PubMed and EMBASE libraries were systematically searched on November 9th, 2022 for randomized controlled trials and observational studies reporting causative mutations in at least five patients with peripheral venous, lymphatic, arteriovenous and combined malformations. Study quality was assessed with the Newcastle-Ottawa Scale. Data were extracted on patient and VM characteristics, molecular sequencing method and results of molecular analysis. In total, 5667 articles were found of which 69 studies were included, reporting molecular analysis in a total of 4261 patients and 1686 (40%) patients with peripheral VMs a causative mutation was detected. In conclusion, this systematic review provides a comprehensive overview of causative germline and somatic mutations in various genes and associated phenotypes in peripheral VMs. With these findings, we attempt to better understand how the underlying causative mutations in various genes contribute to the highly variable clinical characteristics of VMs. Our study shows that some causative mutations lead to a uniform phenotype, while other causal variants lead to more varying phenotypes. By contrast, distinct causative mutations may lead to similar phenotypes and result in almost indistinguishable VMs. VMs are currently classified based on clinical and histopathology features, however, the findings of this systematic review suggest a larger role for genotype in current diagnostics and classification.

PIK3CA inhibition in models of proliferative glomerulonephritis and lupus nephritis

Proliferative glomerulonephritis is a severe condition that often leads to kidney failure. There is a significant lack of effective treatment for these disorders. Here, following the identification of a somatic PIK3CA gain-of-function mutation in podocytes of a patient, we demonstrate using multiple genetically engineered mouse models, single-cell RNA sequencing, and spatial transcriptomics the crucial role played by this pathway for proliferative glomerulonephritis development by promoting podocyte proliferation, dedifferentiation, and inflammation. Additionally, we show that alpelisib, a PI3Kα inhibitor, improves glomerular lesions and kidney function in different mouse models of proliferative glomerulonephritis and lupus nephritis by targeting podocytes. Surprisingly, we determined that pharmacological inhibition of PI3Kα affects B and T lymphocyte populations in lupus nephritis mouse models, with a decrease in the production of proinflammatory cytokines, autoantibodies, and glomerular complement deposition, which are all characteristic features of PI3Kδ inhibition, the primary PI3K isoform expressed in lymphocytes. Importantly, PI3Kα inhibition does not impact lymphocyte function under normal conditions. These findings were then confirmed in human lymphocytes isolated from patients with active lupus nephritis. In conclusion, we demonstrate the major role played by PI3Kα in proliferative glomerulonephritis and show that in this condition, alpelisib acts on both podocytes and the immune system.

Assessment of gene-disease associations and recommendations for genetic testing for somatic variants in vascular anomalies by VASCERN-VASCA

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/ ).

Shear stress and pathophysiological PI3K involvement in vascular malformations

Molecular characterization of vascular anomalies has revealed that affected endothelial cells (ECs) harbor gain-of-function (GOF) mutations in the gene encoding the catalytic α subunit of PI3Kα (PIK3CA). These PIK3CA mutations are known to cause solid cancers when occurring in other tissues. PIK3CA-related vascular anomalies, or "PIKopathies," range from simple, i.e., restricted to a particular form of malformation, to complex, i.e., presenting with a range of hyperplasia phenotypes, including the PIK3CA-related overgrowth spectrum. Interestingly, development of PIKopathies is affected by fluid shear stress (FSS), a physiological stimulus caused by blood or lymph flow. These findings implicate PI3K in mediating physiological EC responses to FSS conditions characteristic of lymphatic and capillary vessel beds. Consistent with this hypothesis, increased PI3K signaling also contributes to cerebral cavernous malformations, a vascular disorder that affects low-perfused brain venous capillaries. Because the GOF activity of PI3K and its signaling partners are excellent drug targets, understanding PIK3CA's role in the development of vascular anomalies may inform therapeutic strategies to normalize EC responses in the diseased state. This Review focuses on PIK3CA's role in mediating EC responses to FSS and discusses current understanding of PIK3CA dysregulation in a range of vascular anomalies that particularly affect low-perfused regions of the vasculature. We also discuss recent surprising findings linking increased PI3K signaling to fast-flow arteriovenous malformations in hereditary hemorrhagic telangiectasias.

Atypical Presentation and Evolution of Necrotizing Enterocolitis as a PIK3CA Pathological Variant

Activating mutation of PIK3CA is linked with cases of overgrowth syndromes and belongs to the PIK3CA-related overgrowth spectrum (PROS). Mutations in this gene are associated with vascular malformations, brain abnormalities, and an increased risk for certain tumors. We report the case of a newborn girl, preterm at 34 weeks of gestation, referred to our center for atypical necrotizing enterocolitis (NEC). At laparotomy, the appearance of the intestinal tract was described as puffy, cauliflower-like with a dark purplish coloration. Subsequently, the colostomy was described as having a consistent proliferative appearance. Medical treatment with sirolimus resulted in minimal improvement. There are no reported cases in the literature of association between NEC and PIK3CA mutation. It is possible that PIK3CA mutation, including the related vascular anomalies, plays a role in the pathogenesis of NEC with this condition.

The VASCERN PPL working group patient pathway for primary and paediatric lymphoedema

Lymphoedema is caused by an imbalance between fluid production and transport by the lymphatic system. This imbalance can be either caused by reduced transport capacity of the lymphatic system or too much fluid production and leads to swelling associated with tissue changes (skin thickening, fat deposition). Its main common complication is the increased risk of developing cellulitis/erysipelas in the affected area, which can worsen the lymphatic function and can be the cause of raised morbidity of the patient if not treated correctly/urgently. The term primary lymphoedema covers a group of rare conditions caused by abnormal functioning and/or development of the lymphatic system. It covers a highly heterogeneous group of conditions. An accurate diagnosis of primary lymphoedema is crucial for the implementation of an optimal treatment plan and management, as well as to reduce the risk of worsening. Patient care is diverse across Europe, and national specialised centres and networks are not available everywhere. The European Reference Network on Rare Multisystemic Vascular Diseases (VASCERN) gathers the best expertise in Europe and provide accessible cross-border healthcare to patients with rare vascular diseases. There are six different working groups in VASCERN, which focus on arterial diseases, hereditary haemorrhagic telangiectasia, neurovascular diseases, lymphoedema and vascular anomalies. The working group Paediatric and Primary Lymphedema (PPL WG) gathers and shares knowledge and expertise in the diagnosis and management of adults and children with primary and paediatric lymphoedema. The members of PPL WG have worked together to produce this opinion statement reflecting strategies on how to approach patients with primary and paediatric lymphoedema. The objective of this patient pathway is to improve patient care by reducing the time to diagnosis, define the best management and follow-up strategies and avoid overuse of resources. Therefore, the patient pathway describes the clinical evaluation and investigations that lead to a clinical diagnosis, the genetic testing, differential diagnosis, the management and treatment options and the patient follow up at expert and local centres. Also, the importance of the patient group participation in the PPL WG is discussed.

Morphological and radiological features of congenital muscular hypertrophy of the upper limb: experience from a tertiary institution

Congenital muscular hypertrophy is a rare overgrowth disorder in the phosphatidylinositol-3-kinase related spectrum. In the past 3 years, ten patients with 11 limbs involved were treated in our centre. The aim of the study was to describe the clinical and radiological deformities of these patients. We documented the characteristic clinical morphological changes, such as hypertrophy, loss of wrist flexion, thumb hyperabduction, finger deviation and skin crease changes in the palm. Radiologically, the mean first metacarpal radial deviation angle of the affected side measured 55° (range 34 to 67) compared to the normal contralateral side 42° (range 32 to 53). The mean intermetacarpal space ratio was 1.2 (range 1.1 to 1.4) and the mean palm width ratio was 1.2 (range 1.1 to 1.3). In this study, we were able to further characterize the radiological and morphological changes of congenital muscular hypertrophy of upper limbs, which would be helpful for establishing the diagnosis and monitor treatment of this rare condition.Level of evidence: IV.

Epidemiology of the disorders of the Pik3ca-related overgrowth spectrum (Pros)

PIK3CA pathogenic variants are responsible for a group of overgrowth syndromes, collectively known as PIK3CA-Related Overgrowth Spectrum (PROS). These gain-of-function variants arise postzygotically, and, according to time of onset, kind of embryonal tissue affected and regional body extension, give rise to heterogeneous phenotypes. PROS rarity and heterogeneity hamper the correct estimation of its epidemiology. Our work represents the first attempt to define the prevalence of PROS according to the established diagnostic criteria and molecular analysis and based on solid demographic data. We assessed the prevalence in Piedmont Region (Italy), including in the study all participants diagnosed with PROS born there from 1998 to 2021. The search identified 37 cases of PROS born across the 25-year period, providing a prevalence of 1:22,313 live births. Molecular analysis was positive in 81.0% of participants. Taking into account the cases with a detected variant in PIK3CA (n = 30), prevalence of molecularly positive PROS was 1:27,519.

Low risk of embryonic and other cancers in PIK3CA-related overgrowth spectrum: Impact on screening recommendations

The PIK3CA-related overgrowth spectrum (PROS) encompasses various conditions caused by mosaic activating PIK3CA variants. PIK3CA somatic variants are also involved in various cancer types. Some generalized overgrowth syndromes are associated with an increased risk of Wilms tumor (WT). In PROS, abdominal ultrasound surveillance has been advocated to detect WT. We aimed to determine the risk of embryonic and other types of tumors in patients with PROS in order to evaluate surveillance relevance. We searched the clinical charts from 267 PROS patients for the diagnosis of cancer, and reviewed the medical literature for the risk of cancer. In our cohort, six patients developed a cancer (2.2%), and Kaplan Meier analyses estimated cumulative probabilities of cancer occurrence at 45 years of age was 5.6% (95% CI = 1.35%-21.8%). The presence of the PIK3CA variant was only confirmed in two out of four tumor samples. In the literature and our cohort, six cases of Wilms tumor/nephrogenic rests (0.12%) and four cases of other cancers have been reported out of 483 proven PIK3CA patients, in particular the p.(His1047Leu/Arg) variant. The risk of WT in PROS being lower than 5%, this is insufficient evidence to recommend routine abdominal imaging. Long-term follow-up studies are needed to evaluate the risk of other cancer types, as well as the relationship with the extent of tissue mosaicism and the presence or not of the variant in the tumor samples.

Targeted next-generation sequencing for detection of PIK3CA mutations in archival tissues from patients with Klippel-Trenaunay syndrome in an Asian population : List the full names and institutional addresses for all authors

BACKGROUND

Klippel-Trenaunay syndrome (KTS) is a rare slow-flow combined vascular malformation with limb hypertrophy. KTS is thought to lie on the PIK3CA-related overgrowth spectrum, but reports are limited. PIK3CA encodes p110α, a catalytic subunit of phosphatidylinositol 3-kinase (PI3K) that plays an essential role in the PI3K/AKT/mammalian target of rapamycin (mTOR) signaling pathway. We aimed to demonstrate the clinical utility of targeted next-generation sequencing (NGS) in identifying PIK3CA mosaicism in archival formalin-fixed paraffin-embedded (FFPE) tissues from patients with KTS.

RESULTS

Participants were 9 female and 5 male patients with KTS diagnosed as capillaro-venous malformation (CVM) or capillaro-lymphatico-venous malformation (CLVM). Median age at resection was 14 years (range, 5-57 years). Median archival period before DNA extraction from FFPE tissues was 5.4 years (range, 3-7 years). NGS-based sequencing of PIK3CA achieved an amplicon mean coverage of 119,000x. PIK3CA missense mutations were found in 12 of 14 patients (85.7%; 6/8 CVM and 6/6 CLVM), with 8 patients showing the hotspot variants E542K, E545K, H1047R, and H1047L. The non-hotspot PIK3CA variants C420R, Q546K, and Q546R were identified in 4 patients. Overall, the mean variant allele frequency for identified PIK3CA variants was 6.9% (range, 1.6-17.4%). All patients with geographic capillary malformation, histopathological lymphatic malformation or macrodactyly of the foot had PIK3CA variants. No genotype-phenotype association between hotspot and non-hotspot PIK3CA variants was found. Histologically, the vessels and adipose tissues of the lesions showed phosphorylation of the proteins in the PI3K/AKT/mTOR signaling pathway, including p-AKT, p-mTOR, and p-4EBP1.

CONCLUSIONS

The PI3K/AKT/mTOR pathway in mesenchymal tissues was activated in patients with KTS. Amplicon-based targeted NGS could identify low-level mosaicism from low-input DNA extracted from FFPE tissues, potentially providing a diagnostic option for personalized medicine with inhibitors of the PI3K/AKT/mTOR signaling pathway.

Somatic mutation spectrum of a Chinese cohort of pediatrics with vascular malformations

BACKGROUND

Somatic mutations of cancer driver genes are found to be responsible for vascular malformations with clinical manifestations ranging from cutaneous birthmarks to life-threatening systemic anomalies. Till now, only a limited number of cases and mutations were reported in Chinese population. The purpose of this study was to describe the somatic mutation spectrum of a cohort of Chinese pediatrics with vascular malformations.

METHODS

Pediatrics diagnosed with various vascular malformations were collected between May 2019 and October 2020 from Beijing Children's Hospital. Genomic DNA of skin lesion of each patient was extracted and sequenced by whole-exome sequencing to identify pathogenic somatic mutations. Mutations with variant allele frequency less than 5% were validated by ultra-deep sequencing.

RESULTS

A total of 67 pediatrics (33 males, 34 females, age range: 0.1-14.8 years) were analyzed. Exome sequencing identified somatic mutations of corresponding genes in 53 patients, yielding a molecular diagnosis rate of 79.1%. Among 29 PIK3CA mutations, 17 were well-known hotspot p.E542K, p.E545K and p.H1047R/L. Non-hotspot mutations were prevalent in patients with PIK3CA-related overgrowth spectrum, accounting for 50.0% (11/22) of detected mutations. The hotspot GNAQ p.R183Q and TEK p.L914F mutations were responsible for the majority of port-wine stain/Sturge-Weber syndrome and venous malformation, respectively. In addition, we identified a novel AKT1 p.Q79K mutation in Proteus syndrome and MAP3K3 p.E387D mutation in verrucous venous malformation.

CONCLUSIONS

The somatic mutation spectrum of vascular malformations in Chinese population is similar to that reported in other populations, but non-hotspot PIK3CA mutations may also be prevalent. Molecular diagnosis may help the clinical diagnosis, treatment and management of these pediatric patients with vascular malformations.

Delineation of the phenotypes and genotypes of facial infiltrating lipomatosis associated with PIK3CA mutations

BACKGROUND

Facial infiltrating lipomatosis (FIL) is a rare congenital disorder characterized by unilateral facial swelling, for which surgery is the prevailing therapeutic option. Several studies have shown that the development of FIL is closely associated with PIK3CA mutations. This study aimed to further identify rare clinical features and underlying molecular variants in patients with FIL.

RESULTS

Eighteen patients were included in this study, and all patients presented with infiltrating adipose tissues confirmed by magnetic resonance imaging. Macrodactyly, polydactyly, hemimegalencephaly and hemihyperplasia were also observed in patients with FIL. In total, eight different PIK3CA mutations were detected in tissues obtained from sixteen patients, including the missense mutations p.His1047Arg (n = 4), p.Cys420Arg (n = 2), p.Glu453Lys (n = 2), p.Glu542Lys (n = 2), p.Glu418Lys (n = 1), p.Glu545Lys (n = 1), and p.His1047Tyr (n = 1) and the deletion mutation p.Glu110del (n = 3). Furthermore, the GNAQ mutation p.Arg183Gln was detected in the epidermal nevus tissue of one patient. Imaging revealed that several patients carrying hotspot mutations had more severe adipose infiltration and skeletal deformities.

CONCLUSIONS

The abundant clinical presentations and genetic profiles of FIL make it difficult to treat. PIK3CA mutations drive the pathogenesis of FIL, and PIK3CA hotspot mutations may lead to more extensive infiltration of lipomatosis. Understanding the molecular variant profile of FIL will facilitate the application of novel PI3K-targeted inhibitors.

Phosphatidylinositol 3 kinase inhibitor-related pneumonitis: a systematic review and meta-analysis

INTRODUCTION

Serious phosphatidylinositol 3 kinase (PI3K) inhibitor-related pneumonitis has raised clinical concerns, and integrated data for this condition are lacking.

METHODS

Randomized controlled trials (RCTs) comparing PI3K inhibitor therapy with control treatments from electronic databases and registrations were searched from inception to 1 April 20231 April 2023seven1 April 2023. The outcomes of our study were the incidence and risk of all-grade and grade ≥ 3 PI3K inhibitor-associated pneumonitis compared with controls.

RESULTS

The meta-analysis included 13 studies comprising 3916 patients. The incidence of all-grade and grade ≥ 3 pneumonitis was 3.7% (82/2210) and 3.0% (35/1162) in patients treated with PI3K inhibitors. PI3K inhibitors significantly increased the risk of all-grade and grade ≥ 3 pneumonitis compared with controls (RR 5.63, 95% CI [2.97, 10.65], P < 0.00001; RR 6.85, 95% CI [2.45, 19.11], P = 0.0002, respectively) with no significant heterogeneity across studies. In terms of different PI3K inhibitors, copanlisib and idelalisib significantly increased the risk of pneumonitis compared to controls (RR 4.99, 95% CI [1.19, 21.01], P = 0.03; RR 5.53, 95% CI [2.35, 13.01], P < 0.0001, respectively).

CONCLUSION

PI3K inhibitors significantly increased the risk of pneumonitis compared with controls, and most cases are severe or even life-threatening.

PROSPERO REGISTRATION NUMBER

CRD42022318878.

The emerging role of PI3K inhibitors for solid tumour treatment and beyond

Phosphoinositide 3-kinases (PI3Ks) play a central role in tumourigenesis with recurrent activating mutations of its p110α subunit (PIK3CA) identified in several tumours. Although several PI3K inhibitors are approved for haematological malignancies, only alpelisib was approved in solid tumours and for the treatment of PIK3CA-related overgrowth spectrum (PROS) syndrome. Traditional PI3K inhibitors inhibit both wild-type and mutant PI3K with almost equal potency, thus limiting their efficacy due to on-target toxicity. Since the initiation of phase I clinical trials investigating next generation allosteric mutant and isoform selective PIK3CA inhibitors, there has been a surge in interest in PIK3CA targeting in solid tumours. Preclinical characterisation of these compounds showed that maximal mutant protein inhibition fails to elicit metabolic and glucose homoeostasis dysregulation, one of the dose limiting toxicities of both selective and pan PI3K inhibitors. While extreme selectivity can be hypothesised to grant activity and safety advantage to these novel agents, on the other hand reduced benefit can be speculated for patients harbouring multiple or rare PIK3CA mutations. This review summarises the current understanding of PI3K alterations and the state-of-the-art treatment strategies in PI3K driven solid tumours, while also exploring the potential intrinsic and acquired resistance mechanisms to these agents, and the emerging role of mutant selective PIK3CA inhibitors.

Germline genetic mutations in pediatric cerebrovascular anomalies: a multidisciplinary approach to screening, testing, and management

OBJECTIVE

Genetic alterations are increasingly recognized as etiologic factors linked to the pathogenesis and development of cerebrovascular anomalies. Their identification allows for advanced screening and targeted therapeutic approaches. The authors aimed to describe the role of a collaborative approach to care and genetic testing in pediatric patients with neurovascular anomalies, with the objectives of identifying what genetic testing recommendations were made, the yield of genetic testing, and the implications for familial screening and management at present and in the future.

METHODS

The authors performed a descriptive retrospective cohort study examining pediatric patients genetically screened through the Pediatric Neurovascular Program of a single treatment center. Patients 18 years of age and younger with neurovascular anomalies, diagnosed radiographically or histopathologically, were evaluated for germline genetic testing. Patient demographic data and germline genetic testing and recommendation, clinical, treatment, and outcome data were collected and analyzed.

RESULTS

Sixty patients were included; 29 (47.5%) were female. The mean age at consultation was 11.0 ± 4.9 years. Diagnoses included cerebral arteriovenous malformations (AVMs) (n = 23), cerebral cavernous malformations (n = 19), non-neurofibromatosis/non-sickle cell moyamoya (n = 8), diffuse cerebral proliferative angiopathy, and megalencephaly-capillary malformation. Of the 56 patients recommended to have genetic testing, 40 completed it. Genetic alterations were found in 13 (23%) patients. Four patients with AVMs had RASA1, GDF2, and ACVRL1 mutations. Four patients with cavernous malformations had Krit1 mutations. One with moyamoya disease had an RNF213 mutation. Three patients with megalencephaly-capillary malformation had PIK3CA mutations, and 1 patient with a cavernous sinus lesion had an MED12 mutation. The majority of AVM patients were treated surgically. Patients with diffuse cerebral proliferative angiopathy were treated medically with sirolimus. At-risk relatives of 3 patients positive for genetic anomalies had also been tested.

CONCLUSIONS

This study demonstrates a role for exploring genetic alterations in the identification and treatment of pediatric neurovascular disease pathogenesis. Germline genetic mutations were found in almost one-quarter of the patients screened in this study, results that helped to identify medically targeted treatment modalities for some pediatric neurovascular patients. Insight into the genetic etiology of vascular anomalies may provide broader clinical implications for risk assessment, family screening, follow-up surveillance, and medical management.

Localized heterochrony integrates overgrowth potential of oncogenic clones

Somatic mutations occur frequently and can arise during embryogenesis, resulting in the formation of a patchwork of mutant clones. Such mosaicism has been implicated in a broad range of developmental anomalies; however, their etiology is poorly understood. Patients carrying a common somatic oncogenic mutation in either PIK3CA or AKT1 can present with disproportionally large digits or limbs. How mutant clones, carrying an oncogenic mutation that often drives unchecked proliferation, can lead to controlled and coordinated overgrowth is unknown. We use zebrafish to explore the growth dynamics of oncogenic clones during development. Here, in a subset of clones, we observed a local increase in proportion of the fin skeleton closely resembling overgrowth phenotypes in patients. We unravel the cellular and developmental mechanisms of these overgrowths, and pinpoint the cell type and timing of clonal expansion. Coordinated overgrowth is associated with rapid clone expansion during early pre-chondrogenic phase of bone development, inducing a heterochronic shift that drives the change in bone size. Our study details how development integrates and translates growth potential of oncogenic clones, thereby shaping the phenotypic consequences of somatic mutations.

Genotypes and phenotypes heterogeneity in PIK3CA-related overgrowth spectrum and overlapping conditions: 150 novel patients and systematic review of 1007 patients with PIK3CA pathogenetic variants

BACKGROUND

Postzygotic activating PIK3CA variants cause several phenotypes within the PIK3CA-related overgrowth spectrum (PROS). Variant strength, mosaicism level, specific tissue involvement and overlapping disorders are responsible for disease heterogeneity. We explored these factors in 150 novel patients and in an expanded cohort of 1007 PIK3CA-mutated patients, analysing our new data with previous literature to give a comprehensive picture.

METHODS

We performed ultradeep targeted next-generation sequencing (NGS) on DNA from skin biopsy, buccal swab or blood using a panel including phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin pathway genes and GNAQ, GNA11, RASA1 and TEK. Additionally, 914 patients previously reported were systematically reviewed.

RESULTS

93 of our 150 patients had PIK3CA pathogenetic variants. The merged PROS cohort showed that PIK3CA variants span thorough all gene domains, some were exclusively associated with specific PROS phenotypes: weakly activating variants were associated with central nervous system (CNS) involvement, and strongly activating variants with extra-CNS phenotypes. Among the 57 with a wild-type PIK3CA allele, 11 patients with overgrowth and vascular malformations overlapping PROS had variants in GNAQ, GNA11, RASA1 or TEK.

CONCLUSION

We confirm that (1) molecular diagnostic yield increases when multiple tissues are tested and by enriching NGS panels with genes of overlapping 'vascular' phenotypes; (2) strongly activating PIK3CA variants are found in affected tissue, rarely in blood: conversely, weakly activating mutations more common in blood; (3) weakly activating variants correlate with CNS involvement, strong variants are more common in cases without; (4) patients with vascular malformations overlapping those of PROS can harbour variants in genes other than PIK3CA.

Undergrowth Of First Toe In PiK3CA-Related Overgrowth Spectrum (PROS)

BACKGROUND

PIK3CA-related overgrowth syndrome (PROS) include a heterogeneous group of disorders characterized by segmental overgrowth secondary to somatic mosaic activating variants in PIK3CA. Segmental undergrowth is more uncommon and has been less studied but pathogenic variants in PIK3CA have also been found. With this in mind, we have noticed a group of patients with PROS that present an undergrowth component associated with their focal overgrowth.

METHODS

Retrospective review of patients with PROS presenting overgrowth of the lower limb and undergrowth of the ipsilateral first toe was performed.

RESULTS

Six patients were included, 4 female and 2 male with a median age of 16.8 years. All patients presented a PROS phenotype with overgrowth of the lower limb and undergrowth of ipsilateral first toe. A PIK3CA pathogenic variant was confirmed in all patients. Patients underwent multiple treatments, currently all are receiving alpelisib with a mean duration of 15.8 months (1-39) and partial response in lipomatosis and vascular anomalies but no response in overgrowth and undergrowth so far.

CONCLUSIONS

Pathogenic variants in the same gene can create different phenotypes depending on the time and place of the mutation. There is little information regarding opposing phenotpyes in the same patient with PROS. The presence of undergrowth in our series might be explained by genetic, embryogenic, maternal, or placental factors but needs to be further investigated.

PIK3CA gain-of-function mutation in adipose tissue induces metabolic reprogramming with Warburg-like effect and severe endocrine disruption

PIK3CA-related overgrowth syndrome (PROS) is a genetic disorder caused by somatic mosaic gain-of-function mutations of PIK3CA. Clinical presentation of patients is diverse and associated with endocrine disruption. Adipose tissue is frequently involved, but its role in disease development and progression has not been elucidated. Here, we created a mouse model of PIK3CA-related adipose tissue overgrowth that recapitulates patient phenotype. We demonstrate that PIK3CA mutation leads to GLUT4 membrane accumulation with a negative feedback loop on insulin secretion, a burst of liver IGFBP1 synthesis with IGF-1 sequestration, and low circulating levels. Mouse phenotype was mainly driven through AKT2. We also observed that PIK3CA mutation induces metabolic reprogramming with Warburg-like effect and protein and lipid synthesis, hallmarks of cancer cells, in vitro, in vivo, and in patients. We lastly show that alpelisib is efficient at preventing and improving PIK3CA-adipose tissue overgrowth and reversing metabolomic anomalies in both animal models and patients.

PIK3CA Mutational Analysis in Patients With Macrodactyly

BACKGROUND

Somatic mosaicism for PIK3CA mutations causes various types of growth disorders, which have been summarized under the term PROS (PIK3CA related overgrowth spectrum). Targeted therapy with PI3K inhibitors seems to be a promising alternative for severe PROS cases. Therefore, PIK3CA testing may become more relevant in the future.

METHODS

We report on 14 PROS patients, who had surgery for macrodactyly in the majority of cases. Clinical data were retrieved from the patient's records. Macroscopic and microscopic findings were retrospectively reviewed. Mutational analysis was performed on formalin-fixed paraffin-embedded (FFPE) material.

RESULTS

Patient age ranged from 7 months to 35 years. Five patients showed additional anomalies. One patient had CLOVES syndrome. The majority of the specimens were ray resections characterized by hypertrophic fat tissue. Overall, microscopy was subtle. The abnormal adipose tissue showed lobules exhibiting at least focally fibrous septa. In each case, we could detect a PIK3CA mutation.

CONCLUSION

Histology of affected fat tissue in PROS patients is overall nonspecific. Therefore, mutational analysis represents the key to the diagnosis, especially in unclear clinical cases. We demonstrated that FFPE material is suitable for PIK3CA testing, which can be considered as basis for targeted therapy with PI3K inhibitors.

Alpelisib for the treatment of PIK3CA-related head and neck lymphatic malformations and overgrowth

PURPOSE

PIK3CA-related overgrowth spectrum (PROS) conditions of the head and neck are treatment challenges. Traditionally, these conditions require multiple invasive interventions, with incomplete malformation removal, disfigurement, and possible dysfunction. Use of the PI3K inhibitor alpelisib, previously shown to be effective in PROS, has not been reported in PIK3CA-associated head and neck lymphatic malformations (HNLMs) or facial infiltrating lipomatosis (FIL). We describe prospective treatment of 5 children with PIK3CA-associated HNLMs or head and neck FIL with alpelisib monotherapy.

METHODS

A total of 5 children with PIK3CA-associated HNLMs (n = 4) or FIL (n = 1) received alpelisib monotherapy (aged 2-12 years). Treatment response was determined by parental report, clinical evaluation, diary/questionnaire, and standardized clinical photography, measuring facial volume through 3-dimensional photos and magnetic resonance imaging.

RESULTS

All participants had reduction in the size of lesion, and all had improvement or resolution of malformation inflammation/pain/bleeding. Common invasive therapy was avoided (ie, tracheotomy). After 6 or more months of alpelisib therapy, facial volume was reduced (range 1%-20%) and magnetic resonance imaging anomaly volume (range 0%-23%) were reduced, and there was improvement in swallowing, upper airway patency, and speech clarity.

CONCLUSION

Individuals with head and neck PROS treated with alpelisib had decreased malformation size and locoregional overgrowth, improved function and symptoms, and fewer invasive procedures.

Multiple congenital malformations arise from somatic mosaicism for constitutively active Pik3ca signaling

Recurrent missense mutations of the PIK3CA oncogene are among the most frequent drivers of human cancers. These often lead to constitutive activation of its product p110α, a phosphatidylinositol 3-kinase (PI3K) catalytic subunit. In addition to causing a broad range of cancers, the H1047R mutation is also found in affected tissues of a distinct set of congenital tumors and malformations. Collectively termed PIK3CA-related disorders (PRDs), these lead to overgrowth of brain, adipose, connective and musculoskeletal tissues and/or blood and lymphatic vessel components. Vascular malformations are frequently observed in PRD, due to cell-autonomous activation of PI3K signaling within endothelial cells. These, like most muscle, connective tissue and bone, are derived from the embryonic mesoderm. However, important organ systems affected in PRDs are neuroectodermal derivatives. To further examine their development, we drove the most common post-zygotic activating mutation of Pik3ca in neural crest and related embryonic lineages. Outcomes included macrocephaly, cleft secondary palate and more subtle skull anomalies. Surprisingly, Pik3ca-mutant subpopulations of neural crest origin were also associated with widespread cephalic vascular anomalies. Mesectodermal neural crest is a major source of non-endothelial connective tissue in the head, but not the body. To examine the response of vascular connective tissues of the body to constitutive Pik3ca activity during development, we expressed the mutation by way of an Egr2 (Krox20) Cre driver. Lineage tracing led us to observe new lineages that had normally once expressed Krox20 and that may be co-opted in pathogenesis, including vascular pericytes and perimysial fibroblasts. Finally, Schwann cell precursors having transcribed either Krox20 or Sox10 and induced to express constitutively active PI3K were associated with vascular and other tumors. These murine phenotypes may aid discovery of new candidate human PRDs affecting craniofacial and vascular smooth muscle development as well as the reciprocal paracrine signaling mechanisms leading to tissue overgrowth.

Defining vascular anomaly phenotypes in children based on a systematic literature search: A critical step in developing a single severity score for interventional clinical trials

INTRODUCTION

Genetically targeted drugs in vascular anomalies (VA) are used despite the absence of a validated severity score. The aim of this study was to evaluate the feasibility of grouping phenotypic VA clinical characteristics into a single severity score.

METHODS

A systematic literature review including children treated with sirolimus accompanied by a detailed description of phenotype and management was conducted. Demographic data and clinical features were extracted to define distinct categories of phenotypes.

RESULTS

Children with VA display two main phenotypes regardless of VA subtype, which may overlap. A systemic phenotype results from direct invasion and compression of vital structures generally leading to hospitalization and aggressive management in infancy. A functional phenotype is associated with chronic pain and disability manifesting mainly during early adolescence and managed in the outpatient setting.

CONCLUSION

The two distinct phenotypes described could be the basis for developing a unified scoring system for VA severity assessment.

How we approach the diagnosis of a vascular anomaly

Vascular anomalies represent a diverse group of complex disorders that can cause significant complications, including coagulopathies, pain, and decreased function. The diagnosis of vascular anomalies is often challenging due to heterogeneity of presenting phenotypes and overlapping clinical features with other pediatric conditions. Pediatric hematologists/oncologists (PHO) are uniquely positioned for an essential role in diagnosing, managing, and coordinating the multidisciplinary care required to maximize the quality of life of these patients. Here, we review the diagnostic approach involved in patients with vascular anomalies and utilize cases to highlight the challenges involved, and how PHOs can play a vital part in the care of these patients.

How we approach complex vascular anomalies and overgrowth syndromes

Vascular anomalies, both vascular tumors and vascular malformations, can occur in isolation or as part of syndromes including those which feature phenotypic overgrowth. To update what is known about vascular anomalies associated with overgrowth, PubMed was searched for "overgrowth syndromes and vascular anomalies or malformations." PubMed, OMIM, and the Rare Disease Database also were searched for specific diagnoses. We review individual overgrowth syndromes, provide a case-based approach to the clinical, radiographic, pathologic, and genetic basis for diagnosis, to complications of both the vascular anomalies and the overgrowth, and emphasize the need for a multidisciplinary approach to care.

Brain Abnormalities in PIK3CA-Related Overgrowth Spectrum: Physician, Patient, and Caregiver Experiences

PIK3CA-related overgrowth spectrum (PROS) disorders are caused by somatic, gain-of-function mutations in PIK3CA (phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha) that result in hyperactivation of the phosphatidylinositol-3-kinase (PI3K) signaling pathway. PROS encompasses a broad spectrum of overlapping phenotypes that vary considerably in their severity and tissue distribution, leading to different and complex experiences for affected children and their families. The parent of a child with the PROS disorder megalencephaly-capillary malformation (MCAP) coauthored this article. MCAP is characterized by significant neurological involvement, and she describes personal experiences with this condition, including delays associated with obtaining a correct diagnosis, finding an experienced care team, challenges with schooling, medical complications, and the ongoing emotional and financial impacts on their lives. A physician perspective, which reinforces the challenges faced by the young child and his family, is provided by a clinician and researcher specializing in PROS disorders with central nervous system involvement. The physician reviews the mechanism of disease, some of the challenges in accurately diagnosing PROS conditions, disease-related complications, current treatment options and their limitations, and emerging therapeutic options including ongoing clinical trials. Our objective is to share these experiences and insights to benefit patients with PROS disorders, their families, and health care professionals involved with caring for patients with PROS.

Postzygotic mutations and where to find them - Recent advances and future implications in the field of non-neoplastic somatic mosaicism

The technological progress of massively parallel sequencing (MPS) has triggered a remarkable development in the research on postzygotic mutations. Although the overwhelming majority of studies in the field focus on oncogenesis, non-neoplastic diseases are attracting more and more attention. The aim of this review was to summarize some of the most recent findings in the field of somatic mosaicism in diseases other than neoplastic events. We discuss the abundance and role of postzygotic mutations, with a special emphasis on disorders which occur only in a mosaic form (obligatory mosaic diseases; OMDs). Based on the list of OMDs compiled from the published literature and three databases (OMIM, Orphanet and MosaicBase), we demonstrate the prevalence of cancer-related genes across OMDs and suggest other sources to further explore OMDs and OMD-related genes. Additionally, we comment on some practical aspects related to mosaic diseases, such as approaches to tissue sampling, the MPS coverage required to detect variants at a very low frequency, as well as on bioinformatic and molecular tools dedicated to detect somatic mutations in MPS data.

Clinical and Molecular Spectrum of Sporadic Vascular Malformations: A Single-Center Study

Sporadic vascular malformations (VMs) are a large group of disorders of the blood and lymphatic vessels caused by somatic mutations in several genes—mainly regulating the RAS/MAPK/ERK and PI3K/AKT/mTOR pathways. We performed a cross-sectional study of 43 patients affected with sporadic VMs, who had received molecular diagnosis by high-depth targeted next-generation sequencing in our center. Clinical and imaging features were correlated with the sequence variants identified in lesional tissues. Six of nine patients with capillary malformation and overgrowth (CMO) carried the recurrent GNAQ somatic mutation p.Arg183Gln, while two had PIK3CA mutations. Unexpectedly, 8 of 11 cases of diffuse CM with overgrowth (DCMO) carried known PIK3CA mutations, and the remaining 3 had pathogenic GNA11 variants. Recurrent PIK3CA mutations were identified in the patients with megalencephaly–CM–polymicrogyria (MCAP), CLOVES, and Klippel–Trenaunay syndrome. Interestingly, PIK3CA somatic mutations were associated with hand/foot anomalies not only in MCAP and CLOVES, but also in CMO and DCMO. Two patients with blue rubber bleb nevus syndrome carried double somatic TEK mutations, two of which were previously undescribed. In addition, a novel sporadic case of Parkes Weber syndrome (PWS) due to an RASA1 mosaic pathogenic variant was described. Finally, a girl with a mild PWS and another diagnosed with CMO carried pathogenic KRAS somatic variants, showing the variability of phenotypic features associated with KRAS mutations. Overall, our findings expand the clinical and molecular spectrum of sporadic VMs, and show the relevance of genetic testing for accurate diagnosis and emerging targeted therapies.

Mapping the PIK3CA-related overgrowth spectrum (PROS) patient and caregiver journey using a patient-centered approach

BACKGROUND

PROS disorders are driven by somatic, gain-of-function mutations in PIK3CA that result in hyperactivation of the phosphatidylinositol-3-kinase (PI3K) signaling pathway. PROS encompasses a broad spectrum of overlapping phenotypes (including overgrowth and vascular malformations) that vary significantly in their severity; every case is unique, leading to different, complex experiences. Here, we aim to describe the PROS experience from the patients' and caregivers' points of view, from onset to diagnosis to treatment and support.

RESULTS

The PROS patient journey was developed using a literature review, an ethnography study, health care professional (HCP) research, and social listening. It was then validated with patients, caregivers, and patient advocates. Physician research included 94 PROS centers and other vascular anomaly centers throughout the United States and Europe. Ethnographic research included 24 patients, caregivers, and/or advocates; selected data from 223 patients were reviewed. Key priority areas of need were identified, along with barriers to and potential enablers of quality care. Visual mapping of the PROS patient and family journey was developed to identify key personal health and system issues, and opportunities for improvements throughout patients' lifespans. Maps were also developed for 3 specific conditions: Klippel-Trénaunay syndrome (K-T); congenital lipomatous overgrowth, vascular malformations, epidermal nevi, scoliosis/skeletal and spinal anomalies (CLOVES) syndrome; and megalencephaly-capillary malformation syndrome (M-CM). Overall, most patients with PROS conditions and their families struggle with a long path to diagnosis, access to genetic testing, and finding qualified specialists. Following diagnosis, patients and families are frequently challenged with major medical events, comorbidities, unpredictability, frequent hospitalization, impact on school and work, the need for multidisciplinary care, unwanted attention, adverse impact on mental and emotional health, and financial pressures. Lack of effective pain management emerged as a substantial issue. Challenges and barriers to quality care shift throughout patients' lifespans; transition from pediatric to adult care can be especially difficult.

CONCLUSIONS

This patient journey in PROS was created in collaboration with patients, caregivers, and advocates as key partners. This novel methodology, which could be applied elsewhere, can more accurately identify areas of unmet need, barriers to care, education topics, and assist HCPs to understand the patient and family perspective.

A Review on Cutaneous and Musculoskeletal Manifestations of CLOVES Syndrome

CLOVES syndrome is a novel sporadic mosaic segmental overgrowth syndrome, currently categorized under the canopy of PROS (PIK3CA-related overgrowth spectrum) disorders. All PROS disorders harbor heterozygous postzygotic activating somatic mutations involving the PIK3CA gene. As an upstream regulator of the PI3K/AKT/mTOR signal transduction pathway, activating mutations of PIK3CA gene commence in uncontrolled growth of cutaneous, vascular (capillaries, veins, and lymphatics), adipose, neural, and musculoskeletal tissues. The excessive growth is segmental, patchy, asymmetric, and confined to body parts affected by the mutation. The term ‘CLOVES’ is an acronym denoting congenital lipomatous overgrowth, vascular malformations, epidermal nevi and spinal (scoliosis) and/ or skeletal anomalies. The syndrome is characterized by an admixture of overgrown tissues, derived mainly from mesoderm and neuroectoderm. Among PROS disorders, CLOVES syndrome represents the extreme end of the spectrum with massive affection of almost the entire body. The syndrome might judiciously be treated with medications hampering with the PI3K/AKT/mTOR signal transduction pathway. This article aims at reviewing the cutaneous and musculoskeletal manifestations of CLOVES syndrome, as the paradigm for PROS disorders. CLOVES syndrome and other PROS disorders are still misdiagnosed, underdiagnosed, underreported, and undertreated by the dermatology community.

The Klippel-Trénaunay Syndrome in 2022: Unravelling Its Genetic and Molecular Profile and Its Link to the Limb Overgrowth Syndromes

The Klippel-Trénaunay syndrome is an unusual syndrome of vascular and dermatologic manifestation in which patients demonstrate hemihypertrophy of the soft tissue and bones of one limb, cutaneous haemangiomas and varicosities in anatomically abnormal positions. Described in 1900 by two French physicians, the etiology remained unclear until recently, when evidence emerged that there was a genetic basis for this sporadic disorder. Genes that encoded pathological angiogenic factors and caused vascular dysmorphogenesis, explaining the molecular bases of this syndrome, were identified. Several angiogenic genes were identified but one gene, the AGGF1 (formerly VG5Q) gene, was seen in mutations involving patients diagnosed with Klippel-Trénaunay syndrome. Furthermore, this syndrome was also noted to have overlapping clinical features linked with the “overgrowth syndromes,” in which genetic mutations along somatic lines were identified. These involved The PI3K enzyme which forms part of the phosphoinositide 3–kinase pathway which is encoded by the PIK3CA-gene. This enzyme mediates embryonic cellular growth in-utero and diseases involved in this pathway are classified as members of the PIK3CA-related overgrowth syndrome. This paper reviews the status of what is now known about the molecular genetics of this unusual, but clinically challenging disorder and its differentiation from similar diseases, linked with the PIK3CA-gene and the related overgrowth syndromes.

Clinical and molecular data in cases of prenatal localized overgrowth disorder: major implication of genetic variants in PI3K-AKT-mTOR signaling pathway

OBJECTIVES

To describe clinical and molecular findings in a French multicenter cohort of fetuses with prenatal diagnosis of congenital abnormality and suspicion of a localized overgrowth disorder (LOD) suggestive of genetic variants in the PI3K-AKT-mTOR signaling pathway.

METHODS

We analyzed retrospectively data obtained between 1 January 2013 and 1 May 2020 from fetuses with brain and/or limb overgrowth referred for molecular diagnosis of PI3K-AKT-mTOR pathway genes by next-generation sequencing (NGS) using pathological tissue obtained by fetal autopsy. We also assessed the diagnostic yield of amniotic fluid.

RESULTS

During the study period, 21 subjects with LOD suspected of being secondary to a genetic variant of the PI3K-AKT-mTOR pathway were referred for analysis. Of these, 17 fetuses had brain overgrowth, including six with isolated megalencephaly (MEG) and 11 with hemimegalencephaly (HMEG). Of the six with MEG, germline variants were identified in four cases, in either PIK3R2, AKT3 or MTOR, and a postzygotic PIK3R2 variant was found in the other two cases. Of the 11 with HMEG, a postzygotic PIK3CA variant was found in three fetuses with extracerebral features of PIK3CA-related overgrowth spectrum, and in seven fetuses with isolated HMEG. No pathogenic variant was identified in the 11^th case with HMEG. Four fetuses with limb overgrowth also had one or more lymphatic malformations (LM) and harbored a postzygotic PIK3CA variant. NGS on cultured amniocytes performed in 10 cases, of which nine had been found positive on analysis of pathological fetal tissue, showed variants in four, in either PIK3CA, PIK3R2 or AKT3.

CONCLUSIONS

Isolated MEG or HMEG may lead to identification of genetic variants in the PI3K-AKT-mTOR signaling pathway. Cases of limb overgrowth and LM or isolated HMEG are likely associated with PIK3CA variants. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Update of Pediatric Lipomatous Lesions: A Clinicopathological, Immunohistochemical and Molecular Overview

Lipomatous neoplasms are a rare entity in the pediatric population, comprising less than 10% of soft tissue tumors in the first two decades of life. Some characteristics of pediatric adipocytic tumors are analogous to their adult counterparts, some pediatric lipomatous lesions however harbor unique features. In recent years, there have been significant advances in the understanding of the pathogenesis and hence in the classification and treatment of pediatric adipocytic tumors. This literature-based article will provide a review of the presently known clinicopathological, immunohistochemical and molecular features of pediatric lipomatous lesions.

Phenotypic and molecular characterization of five patients with PIK3CA-related overgrowth spectrum (PROS)

Somatic and germline PI3K-AKT-mTOR pathway pathogenic variants are involved in several segmental overgrowth phenotypes such as the PIK3CA-related overgrowth spectrum (PROS), Proteus syndrome, and PTEN hamartoma tumor syndrome. In this study, we describe five patients with PROS. We identified by high-throughput sequencing four different somatic PIK3CA pathogenic variants in five individuals. The Glu726Lys variant, which was previously reported in megalencephaly-capillary malformation-polymicrogyria (MCAP) syndrome, was identified in two patients with unclassified PROS. The Cys420Arg substitution, which was previously reported in CLOVES, was found in a patient with fibroadipose hyperplasia. Additionally, relatively rare pathogenic variants, His1047Tyr and Tyr1021Cys, were detected in two patients with MCAP. Therefore, we suggest performing deep sequencing of PIK3CA in all patients with suspected PROS, instead of targeted polymerase chain reaction for hotspot pathogenic variants.

Update of pediatric soft tissue tumors with review of conventional MRI appearance-part 1: tumor-like lesions, adipocytic tumors, fibroblastic and myofibroblastic tumors, and perivascular tumors

There are numerous soft tissue tumors and tumor-like conditions in the pediatric population. Magnetic resonance imaging is the most useful modality for imaging these lesions. Although certain soft tissue lesions exhibit magnetic resonance features characteristic of a specific diagnosis, most lesions are indeterminate, and a biopsy is necessary for diagnosis. We provide a detailed update of soft tissue tumors and tumor-like conditions that occur in the pediatric population, emphasizing each lesion's conventional magnetic resonance imaging appearance, using the recently released 5th edition of the World Health Organization Classification of Soft Tissue and Bone Tumors as a guide. In part one of this review, pediatric tumor-like lesions, adipocytic tumors, fibroblastic and myofibroblastic tumors, and perivascular tumors are discussed. In part two, vascular lesions, fibrohistiocytic tumors, muscle tumors, peripheral nerve sheath tumors, tumors of uncertain differentiation, and undifferentiated small round cell sarcomas are reviewed. Per the convention of the WHO, these lesions involve the connective, subcutaneous, and other non-parenchymatous-organ soft tissues, as well as the peripheral and autonomic nervous system.

The long-term progression of macrodactyly

BACKGROUND

Macrodactyly is a rare congenital disorder of overgrowth affecting the digits of the upper or lower extremity. Mostly, patients are surgically treated during childhood to reduce the digit or to stop growth. There are no standardized guidelines for the treatment and follow-up of macrodactyly. Consequently, follow-up may not be regularly scheduled into adulthood.

METHODS

A retrospective, descriptive analysis of patients with the long-term progression of macrodactyly who presented at our tertiary referral hospital between July 2018 and March 2020 was performed. All patients from our local macrodactyly database were screened for progression of macrodactyly since adulthood; this resulted in four patients. The aim of these case series is to highlight the clinical features and disease course at long-term follow-up.

RESULTS

All patients were surgically treated during childhood and showed progression of tissue overgrowth during adult life. All patients developed severe secondary degenerative bone changes in macrodactyly affected digits, such as ankyloses of joints, new bone formation, and bony spurs. Subsequently, tissue overgrowth and degenerative bone changes led to functional problems.

CONCLUSION

Patients with macrodactyly may experience growth during adult life, which may progress to deforming changes. Consequently, patients should be informed about the possible growth, and the progressive growth should be monitored.

Targeted treatment of vascular anomalies

Vascular anomalies comprise an array of congenital developmental disorders that can lead to significant disfigurement and physiologic disarray. The vast multitude of clinical phenotypes has inherently led to misdiagnosis and patients and families enduring long diagnostic odysseys of medical care. Although the observed variation in disease manifestations remains poorly understood, targeted next-generation sequencing has pivoted our understanding of the pathobiology of vascular anomalies and, for the first time, uncovered potential pharmacologic targets for these disorders. In this review article, we highlight current and developing targeted therapies for vascular anomalies, namely phosphoinositide 3-kinase and mitogen-activated protein kinase pathway inhibitors, and discuss the future directions of targeted therapies.

Complex vascular anomalies and tissue overgrowth of limbs associated with increased skin temperature and peripheral venous dilatation: parks weber syndrome or PROS?

PIK3CA-related overgrowth spectrum (PROS) is a series of congenital, sporadic disorders that are associated with segmental overgrowth phenotypes and postzygotic, somatic gene mutations in the PIK3CA-ATK-mTOR pathway. The variability and overlapping phenotypes between PROS and other complex vascular malformations make the differential diagnosis confusing and challenging. PROS should be considered for the differential diagnosis with other complex vascular malformations and syndromes with a tissue overgrowth phenotype, such as Parkes-Weber syndrome (PWS).

Herein, we diagnosed one unique clinically challenging case manifested as capillary malformation (CM), limb overgrowth, as well as increased skin temperature and peripheral venous dilatation of lower limb that indicated a potential fast-flow lesion. The patient was initially diagnosed with PWS. Contrary to the previous diagnosis, based on further MR imaging and digital subtraction angiography (DSA), which ruled out the existence of AVMs and AVFs, and molecular analysis with targeted next-generation sequencing (NGS) revealing a somatic PIK3CA mutation, we ultimately diagnosed that the patient had a unique form of PROS simulating PWS phenotypes. We suggest that it is important to propose the differential diagnosis of PWS and PROS, two diseases that share a common overgrowth phenotype. We recommended radiological diagnosis such as MRI, CT and DSA as well as further molecular diagnosis to provide more information for the assessment of vascular lesions and to further guide clinical treatment strategies.

A standard of care for individuals with PIK3CA-related disorders: An international expert consensus statement

Growth promoting variants in PIK3CA cause a spectrum of developmental disorders, depending on the developmental timing of the mutation and tissues involved. These phenotypically heterogeneous entities have been grouped as PIK3CA-Related Overgrowth Spectrum disorders (PROS). Deep sequencing technologies have facilitated detection of low-level mosaic, often necessitating testing of tissues other than blood. Since clinical management practices vary considerably among healthcare professionals and services across different countries, a consensus on management guidelines is needed. Clinical heterogeneity within this spectrum leads to challenges in establishing management recommendations, which must be based on patient-specific considerations. Moreover, as most of these conditions are rare, affected families may lack access to the medical expertise that is needed to help address the multi-system and often complex medical issues seen with PROS. In March 2019, macrocephaly-capillary malformation (M-CM) patient organizations hosted an expert meeting in Manchester, United Kingdom, to help address these challenges with regards to M-CM syndrome. We have expanded the scope of this project to cover PROS and developed this consensus statement on the preferred approach for managing affected individuals based on our current knowledge.

Treatment strategies for mosaic overgrowth syndromes of the PI3K-AKT-mTOR pathway

INTRODUCTION OR BACKGROUND

Mosaic overgrowth syndromes (OS) are a proteiform ensemble of rare diseases displaying asymmetric overgrowth involving any tissue type, with degrees of severity ranging from isolated malformation to life-threatening conditions such as pulmonary embolism. Despite discordant clinical presentations, all those syndromes share common genetic anomalies: somatic mutations of genes involved in cell growth and proliferation. The PI3K-AKT-mTOR signaling pathway is one of the most prominent regulators of cell homeostasis, and somatic oncogenic mutations affecting this pathway are responsible for mosaic OS. This review aims to describe the clinical and molecular characteristics of the main OS involving the PI3K-AKT-mTOR pathway, along with the treatments available or under development.

SOURCES OF DATA

This review summarizes available data regarding OS in scientific articles published in peer-reviewed journals.

AREAS OF AGREEMENT

OS care requires a multidisciplinary approach relying on clinical and radiological follow-up along with symptomatic treatment. However, no specific treatment has yet shown efficacy in randomized control trials.

AREAS OF CONTROVERSY

Clinical classifications of OS led to frequent misdiagnosis. Moreover, targeted therapies directed at causal mutated proteins are developing in OSs through cancer drugs repositioning, but the evidence of efficacy and tolerance is still lacking for most of them.

GROWING POINTS

The genetic landscape of OS is constantly widening and molecular classifications tend to increase the accuracy of diagnosis, opening opportunities for targeted therapies.

AREAS TIMELY FOR DEVELOPING RESEARCH

OS are a dynamic, expanding field of research. Studies focusing on the identification of genetic anomalies and their pharmacological inhibition are needed.

Mosaicism and the taxonomy of human disease

Two papers in this special issue of Cold Spring Harbor Molecular Case Studies on Mosaicism throw light on an interesting conundrum in mosaic disorders. This conundrum centers on thresholds for the definition of mosaic disorders and how to reconcile the incredible inter- and intrapatient variability of mosaic disorders with the clinical imperative to have clear and distinct categorical diagnoses.

Hypoglycemia due to PI3K/AKT/mTOR signaling pathway defects: two novel cases and review of the literature

INTRODUCTION

The PI3K/AKT/mTOR signaling pathway is important for the regulation of multiple biological processes, including cellular growth and glucose metabolism. Defects of the PI3K/AKT/mTOR signaling pathway are not usually considered among the genetic causes of recurrent hypoglycemia in childhood. However, accumulating evidence links hypoglycemia with defects of this pathway.

CASE REPORTS AND REVIEW

We describe here two cases of macrocephaly and hypoglycemia bearing genetic defects in genes involved in the PI3K/AKT/mTOR pathway. The first patient was diagnosed with a PTEN hamartoma tumour syndrome (PTHS) due to the de novo germline missense mutation c.[492 + 1G > A] of the PTEN gene. The second patient presented the autosomal dominant mental retardation-35 (MDR35) due to the heterozygous missense mutation c.592G > A in the PPP2R5D gene. A review of the literature on hypoglycemia and PI3K/AKT/mTOR signaling pathway defects, with a special focus on the metabolic characterization of hypoglycemia, is included.

CONCLUSIONS

PI3K/AKT/mTOR pathway defects should be included in the differential diagnosis of patients with hypoglycemia and macrocephaly. Clinical suspicion and molecular confirmation are important, not just for an accurate genetic counselling but also for defining the follow-up management, including cancer surveillance. The biochemical profile of hypoglycemia varies among patients. While most patients are characterized by low plasmatic insulin levels, hyperinsulinemia has also been observed. Large patient cohorts are needed to gain a comprehensive profile of the biochemical patterns of hypoglycemia in such defects and eventually guide targeted therapeutic interventions.

Acne Syndromes and Mosaicism

Abnormal mosaicism is the coexistence of cells with at least two genotypes, by the time of birth, in an individual derived from a single zygote, which leads to a disease phenotype. Somatic mosaicism can be further categorized into segmental mosaicism and nonsegmental somatic mosaicism. Acne is a chronic illness characterized by inflammatory changes around and in the pilosebaceous units, commonly due to hormone- and inflammatory signaling-mediated factors. Several systemic disorders, such as congenital adrenal hyperplasia, polycystic ovarian syndrome, and seborrhoea-acne-hirsutism-androgenetic alopecia syndrome have classically been associated with acne. Autoinflammatory syndromes, including PAPA, PASH, PAPASH, PsAPASH, PsaPSASH, PASS, and SAPHO syndromes include acneiform lesions as a key manifestation. Mosaic germline mutations in the FGFR2 gene have been associated with Apert syndrome and nevus comedonicus, two illnesses that are accompanied by acneiform lesions. In this review, we summarize the concept of cutaneous mosaicism and elaborate on acne syndromes, as well as acneiform mosaicism.

Multiple symmetric and multiple familial lipomatosis

Lipomas are the most common soft tissue tumors and are malignant in only 1% of cases. Lipomatosis is defined as the presence of multiple benign lipomas on the body, without lipoatrophy. Their impact on quality of life is significant. Different entities have been described such as symmetrical multiple lipomatosis (MSL), also called Madelung's disease and familial multiple lipomatosis (FML). MSL occurs preferentially in men (but also women) who are alcohol abuser. There are different subtypes of the disease, the most classic of which affects the upper body and the nuchal region with a buffalo hump appearance. A metabolic component with obesity is frequent. In contrast to Dercum's disease, there is no pain. SAOS, complications of the metabolic syndrome and of alcohol abuse including cancers, may be associated and should be screened. FML has been little described in the literature since Brodie's first report in 1846. FML occurs preferentially in the third decade but equally in women and men. Its autosomal dominant component is classically accepted with variable penetrance within the same family. Association with naevi, angiomas, polyneuropathies and with gastrointestinal comorbidities has been reported. Interestingly, and in contrast with most lipodystrophy disorders, the patients show an insulin sensitivity profile. A better understanding of the underlying pathophysiological mechanisms would open up avenues on therapeutic research, since treatments are only symptomatic to date.

Newcomers in Vascular Anomalies

Vascular anomalies are composed of tumors and malformations and with overlapping histologies, thus are often misdiagnosed or labeled with imprecise terminology. Lesions are common and usually diagnosed during infancy or childhood; the estimated prevalence is 4.5%. Vascular tumors rapidly enlarge postnatally and demonstrate endothelial proliferation. Malformations are errors in vascular development with stable endothelial turnover; they are typically named based on the primary vessel that is malformed (capillary, arterial, venous, lymphatic). This article reviews the pathologic and molecular genetic characteristics for select recently described vascular anomalies.

Ubiquitous expression of Akt1 p.(E17K) results in vascular defects and embryonic lethality in mice

Proteus syndrome is a progressive overgrowth disorder with vascular malformations caused by mosaic expression of the AKT1 c.49G > A, p.(E17K) activating variant which was predicted to cause lethality if expressed ubiquitously. To test that hypothesis, we used the ACTB-Cre gene to activate a conditional Akt1 p.(E17K) allele in the mouse. No offspring that was heterozygous for both Cre and the conditional allele (βA-Akt1WT/flx) was viable. Fewer than expected numbers of βA-Akt1WT/flx embryos were seen beginning at E11.5, but a few survived until E17.5. The phenotype ranged from mild to severe, but generally βA-Akt1WT/flx embryos had fewer visible blood vessels and more hemorrhages than their wild-type littermates, which was suggestive of a vascular abnormality. Examination of E13.5 limb skin showed a primitive capillary network with increased branching complexity and abnormal patterning compared with wild-type skin. By E15.5, wild-type skin had undergone angiogenesis and formed a hierarchical network of remodeled vessels, whereas in βA-Akt1WT/flx embryos, the capillary network failed to remodel. Mural cell coverage of the blood vessels was also reduced in βA-Akt1WT/flx skin compared with that of wild type. Restricting expression of Akt1E17K to endothelial, cardiac or smooth muscle cells resulted in viable offspring and remodeled vasculature and did not recapitulate the βA-Akt1WT/flx phenotype. We conclude that ubiquitous expression of Akt1E17K suppresses remodeling and inhibits the formation of a normal skin vasculature. We postulate that this failure prevents proper circulation necessary to support the growing embryo and that it is the result of interactions of multiple cell types with increased AKT signaling.