Mosaic Activating Mutations in FGFR1 Cause Encephalocraniocutaneous Lipomatosis

Exploring New Drug Repurposing Opportunities for MEK Inhibitors in RASopathies: A Comprehensive Review of Safety, Efficacy, and Future Perspectives of Trametinib and Selumetinib

The RASopathies are a group of syndromes caused by genetic variants that affect the RAS-MAPK signaling pathway, which is essential for cell response to diverse stimuli. These variants functionally converge towards the overactivation of the pathway, leading to various constitutional and mosaic conditions. These syndromes show overlapping though distinct clinical presentations and share congenital heart defects, hypertrophic cardiomyopathy (HCM), and lymphatic dysplasia as major clinical features, with highly variable prevalence and severity. Available treatments have mainly been directed to target the symptoms. However, repurposing MEK inhibitors (MEKis), which were originally developed for cancer treatment, to target evolutive aspects occurring in these disorders is a promising option. Animal models have shown encouraging results in treating various RASopathy manifestations, including HCM and lymphatic abnormalities. Clinical reports have also provided first evidence supporting the effectiveness of MEKi, especially trametinib, in treating life-threatening conditions associated with these disorders. Nevertheless, despite notable improvements, there are adverse events that occur, necessitating careful monitoring. Moreover, there is evidence indicating that multiple pathways can contribute to these disorders, indicating a current need to more accurate understand of the underlying mechanism of the disease to apply an effective targeted therapy. In conclusion, while MEKi holds promise in managing life-threatening complications of RASopathies, dedicated clinical trials are required to establish standardized treatment protocols tailored to take into account the individual needs of each patient and favor a personalized treatment.

Encephalocraniocutaneous lipomatosis phenotype associated with mosaic biallelic pathogenic variants in the NF1 gene

Encephalocraniocutaneous lipomatosis (ECCL) is a sporadic congenital condition characterised by ocular, cutaneous and central nervous system involvement. Mosaic activating variants in FGFR1 and KRAS have been reported in several individuals with this syndrome. We report on a patient with neurofibromatosis type 1 (NF1) with a germline pathogenic variant in the NF1 gene and an ECCL phenotype, suggesting ECCL to be part of a spectrum of malformations associated with NF1 pathogenic variants. An anatomical hemispherectomy was performed for intractable epilepsy. Through genetic analysis of blood, cerebral tissue and giant cell lesions in both jaws, we identified the germline NF1 pathogenic variant in all samples and a second-hit pathogenic NF1 variant in cerebral tissue and both giant cell lesions. Both NF1 variants were located on different alleles resulting in somatic mosaicism for a biallelic NF1 inactivation originating in early embryogenesis (second-hit mosaicism or Happle type 2 mosaicism). The biallelic deficit in NF1 in the left hemicranium explains the severe localised, congenital abnormality in this patient. Identical first and second-hit variants in a giant cell lesion of both upper and lower jaws provide confirmatory evidence for an early embryonic second hit involving at least the neural crest. We suggest that the ECCL phenotype may be part of a spectrum of congenital problems associated with mosaic NF1 nullisomy originating during early embryogenesis. The biallelic NF1 inactivation during early embryogenesis mimics the severe activation of the RAS-MAPK pathway seen in ECCL caused by embryonic mosaic activating FGFR1 and KRAS variants in the cranial region. We propose that distinct mechanisms of mosaicism can cause the ECCL phenotype through convergence on the RAS-MAPK pathway.

Mosaic RASopathies concept: different skin lesions, same systemic manifestations?

BACKGROUND

Cutaneous epidermal nevi are genotypically diverse mosaic disorders. Pathogenic hotspot variants in HRAS, KRAS, and less frequently, NRAS and BRAF may cause isolated keratinocytic epidermal nevi and sebaceous nevi or several different syndromes when associated with extracutaneous anomalies. Therefore, some authors suggest the concept of mosaic RASopathies to group these different disorders.

METHODS

In this paper, we describe three new cases of syndromic epidermal nevi caused by mosaic HRAS variants: one associating an extensive keratinocytic epidermal nevus with hypomastia, another with extensive mucosal involvement and a third combining a small sebaceous nevus with seizures and intellectual deficiency. Moreover, we performed extensive literature of all cases of syndromic epidermal nevi and related disorders with confirmed pathogenic postzygotic variants in HRAS, KRAS, NRAS or BRAF.

RESULTS

Most patients presented with bone, ophthalmological or neurological anomalies. Rhabdomyosarcoma, urothelial cell carcinoma and pubertas praecox are also repeatedly reported. KRAS pathogenic variants are involved in 50% of the cases, especially in sebaceous nevi, oculoectodermal syndrome and encephalocraniocutaneous lipomatosis. They are frequently associated with eye and brain anomalies. Pathogenic variants in HRAS are rather present in syndromic keratinocytic epidermal nevi and phacomatosis pigmentokeratotica.

CONCLUSION

This review delineates genotype/phenotype correlations of syndromic epidermal nevi with somatic RAS and BRAF pathogenic variants and may help improve their follow-up.

Human embryonic genetic mosaicism and its effects on development and disease

Nearly every mammalian cell division is accompanied by a mutational event that becomes fixed in a daughter cell. When carried forward to additional cell progeny, a clone of variant cells can emerge. As a result, mammals are complex mosaics of clones that are genetically distinct from one another. Recent high-throughput sequencing studies have revealed that mosaicism is common, clone sizes often increase with age and specific variants can affect tissue function and disease development. Variants that are acquired during early embryogenesis are shared by multiple cell types and can affect numerous tissues. Within tissues, variant clones compete, which can result in their expansion or elimination. Embryonic mosaicism has clinical implications for genetic disease severity and transmission but is likely an under-recognized phenomenon. To better understand its implications for mosaic individuals, it is essential to leverage research tools that can elucidate the mechanisms by which expanded embryonic variants influence development and disease.

Encephalocraniocutaneous Lipomatosis: A Case Report

ABSTRACT

Encephalocraniocutaneous lipomatosis (ECCL) is a rare congenital syndrome and subclassification of oculoectodermal syndrome. Encephalocraniocutaneous lipomatosis may be associated with postzygotic mutations. However, absence of an identifiable mutation does not preclude a diagnosis of ECCL. Encephalocraniocutaneous lipomatosis commonly causes skin, eye, and central nervous system anomalies. Diagnosis can be made through genetic sequencing or standardized clinical criteria. One clinically apparent major criterion for the diagnosis of ECCL is nevus psiloliparus (NP), a fatty nevus with overlying nonscarring alopecia. In this case, a 50-day-old female infant with uncomplicated birth history presented to dermatology clinic for evaluation of 2 superficial cranial masses that had been present since birth without regression or evolution. One of the masses was located within the hairline and demonstrated overlying nonscarring alopecia, suspicious of NP. Because of concern for ECCL, brain magnetic resonance imaging was ordered and revealed 2 intracranial lipomas. Genetic testing was inconclusive. Excision of the masses was performed at the request of the parents for cosmetic purposes. Histologic evaluation of the surgical specimens confirmed the diagnosis of NP and ECCL. A suspected NP should raise concern for ECCL and prompt further evaluation for systemic involvement. In particular, patients with suspected ECCL should be screened for ocular and CNS involvement. Early identification and diagnosis are important for prognostication because patients with ECCL are at increased risk of developing neoplasms of the head and neck and may require more frequent screening examinations.

Navigating the complexities of encephalocraniocutaneous lipomatosis: a case series and review

INTRODUCTION

Encephalocraniocutaneous lipomatosis (ECCL) is a rare congenital syndrome with complex skin, eye, and central nervous system (CNS) symptoms. Diagnosis and treatment are challenging due to its rarity and diverse manifestations. It often involves issues like porencephalic cysts, cortical atrophy, and low-grade gliomas in the CNS, resulting in developmental delays. The spinal cord is frequently affected, leading to problems like medullary compression and radiculopathy, causing back pain and sensory/motor deficits. Surgical interventions are reserved for symptomatic cases to address hydrocephalus or alleviate spinal lipomas. This article reviews a case series to assess surgical risks and neurological outcomes.

CASE SERIES

We present a case series ECCL, focusing on the diffuse lipomatosis of the spinal cord and the intricate surgical procedures involved. A multi-stage surgical approach was adopted, with continuous neuromonitoring employed to safeguard motor pathways. We discuss clinical characteristics, imaging studies, and indications for neurosurgical interventions.

DISCUSSION

ECCL is a complex syndrome. Diagnosis is challenging and includes clinical evaluation, neuroimaging, and genetic testing. Treatment targets specific symptoms, often requiring surgery for issues like lipomas or cerebral cysts. Surgery involves laminectomies, spinal fusion, and motor pathway monitoring. Thorough follow-up is crucial due to potential CNS complications like low-grade gliomas. Hydrocephalus occurs in some cases, with endoscopic third ventriculostomy (ETV) preferred over ventriculoperitoneal shunt placement.

CONCLUSION

Neurosurgery for ECCL is for symptomatic cases. ETV is preferred for hydrocephalus, while the treatment for lipoma is based on the presence of symptoms; the follow-up should assess growth and prevent deformities.

Expansion of the complex genotypic and phenotypic spectrum of FGFR2-associated neurocutaneous syndromes

The fibroblast growth factor receptors comprise a family of related but individually distinct tyrosine kinase receptors. Within this family, FGFR2 is a key regulator in many biological processes, e.g., cell proliferation, tumorigenesis, metastasis, and angiogenesis. Heterozygous activating non-mosaic germline variants in FGFR2 have been linked to numerous autosomal dominantly inherited disorders including several craniosynostoses and skeletal dysplasia syndromes. We report on a girl with cutaneous nevi, ocular malformations, macrocephaly, mild developmental delay, and the initial clinical diagnosis of Schimmelpenning-Feuerstein-Mims syndrome, a very rare mosaic neurocutaneous disorder caused by postzygotic missense variants in HRAS, KRAS, and NRAS. Exome sequencing of blood and affected skin tissue identified the mosaic variant c.1647=/T > G p.(Asn549=/Lys) in FGFR2, upstream of the RAS signaling pathway. The variant is located in the tyrosine kinase domain of FGFR2 in a region that regulates the activity of the receptor and structural mapping and functional characterization revealed that it results in constitutive receptor activation. Overall, our findings indicate FGFR2-associated neurocutaneous syndrome as the accurate clinical-molecular diagnosis for the reported individual, and thereby expand the complex genotypic and phenotypic spectrum of FGFR-associated disorders. We conclude that molecular analysis of FGFR2 should be considered in the genetic workup of individuals with the clinical suspicion of a mosaic neurocutaneous condition, as the knowledge of the molecular cause might have relevant implications for genetic counseling, prognosis, tumor surveillance and potential treatment options.

Next generation sequencing aids diagnosis and management in a case of encephalocraniocutaneous lipomatosis

Encephalocraniocutaneous lipomatosis (ECCL) is a rare neurocutaneous disorder caused by somatic FGFR1 and KRAS variants. It shares significant phenotypic overlap with several closely related disorders caused by mutations in the RAS-MAPK pathway (mosaic RASopathies). We report a diagnostically challenging case of ECCL in which next-generation sequencing of affected tissue identified a pathologic FGFR1 p.K656E variant, thereby establishing a molecular diagnosis. Patients with FGFR1-associated ECCL carry a risk of developing malignant brain tumors; thus, genetic testing of patients with suspected ECCL has important management implications.

Expanding the Clinical Utility of Targeted RNA Sequencing Panels beyond Gene Fusions to Complex, Intragenic Structural Rearrangements

Gene fusions are a form of structural rearrangement well established as driver events in pediatric and adult cancers. The identification of such events holds clinical significance in the refinement, prognostication, and provision of treatment in cancer. Structural rearrangements also extend beyond fusions to include intragenic rearrangements, such as internal tandem duplications (ITDs) or exon-level deletions. These intragenic events have been increasingly implicated as cancer-promoting events. However, the detection of intragenic rearrangements may be challenging to resolve bioinformatically with short-read sequencing technologies and therefore may not be routinely assessed in panel-based testing. Within an academic clinical laboratory, over three years, a total of 608 disease-involved samples (522 hematologic malignancy, 86 solid tumors) underwent clinical testing using Anchored Multiplex PCR (AMP)-based RNA sequencing. Hematologic malignancies were evaluated using a custom Pan-Heme 154 gene panel, while solid tumors were assessed using a custom Pan-Solid 115 gene panel. Gene fusions, ITDs, and intragenic deletions were assessed for diagnostic, prognostic, or therapeutic significance. When considering gene fusions alone, we report an overall diagnostic yield of 36% (37% hematologic malignancy, 41% solid tumors). When including intragenic structural rearrangements, the overall diagnostic yield increased to 48% (48% hematologic malignancy, 45% solid tumor). We demonstrate the clinical utility of reporting structural rearrangements, including gene fusions and intragenic structural rearrangements, using an AMP-based RNA sequencing panel.

DECIPHER: Improving Genetic Diagnosis Through Dynamic Integration of Genomic and Clinical Data

DECIPHER (Database of Genomic Variation and Phenotype in Humans Using Ensembl Resources) shares candidate diagnostic variants and phenotypic data from patients with genetic disorders to facilitate research and improve the diagnosis, management, and therapy of rare diseases. The platform sits at the boundary between genomic research and the clinical community. DECIPHER aims to ensure that the most up-to-date data are made rapidly available within its interpretation interfaces to improve clinical care. Newly integrated cardiac case-control data that provide evidence of gene-disease associations and inform variant interpretation exemplify this mission. New research resources are presented in a format optimized for use by a broad range of professionals supporting the delivery of genomic medicine. The interfaces within DECIPHER integrate and contextualize variant and phenotypic data, helping to determine a robust clinico-molecular diagnosis for rare-disease patients, which combines both variant classification and clinical fit. DECIPHER supports discovery research, connecting individuals within the rare-disease community to pursue hypothesis-driven research.

Mendelian inheritance revisited: dominance and recessiveness in medical genetics

Understanding the consequences of genotype for phenotype (which ranges from molecule-level effects to whole-organism traits) is at the core of genetic diagnostics in medicine. Many measures of the deleteriousness of individual alleles exist, but these have limitations for predicting the clinical consequences. Various mechanisms can protect the organism from the adverse effects of functional variants, especially when the variant is paired with a wild type allele. Understanding why some alleles are harmful in the heterozygous state - representing dominant inheritance - but others only with the biallelic presence of pathogenic variants - representing recessive inheritance - is particularly important when faced with the deluge of rare genetic alterations identified by high throughput DNA sequencing. Both awareness of the specific quantitative and/or qualitative effects of individual variants and the elucidation of allelic and non-allelic interactions are essential to optimize genetic diagnosis and counselling.

Mosaic RASopathies: A review of disorders caused by somatic pathogenic variants in the genes of the RAS/MAPK pathway

Mosaic RASopathies are a heterogeneous group of diseases characterized by the presence at birth or early onset of congenital anomalies, cutaneous and vascular anomalies, segmental overgrowth, and increased cancer risk. They are caused by somatic pathogenic variants of the genes belonging the RAt Sarcoma Mitogen-activated protein kinase (RAS/MAPK) pathway causing its hyperactivation. Here, we review the clinical and molecular characteristics of this heterogeneous group of diseases, including the possibilities of molecular diagnosis and new therapeutic perspectives.

Encephalocraniocutaneous Lipomatosis, a Radiological Challenge: Two Atypical Case Reports and Literature Review

Encephalocraniocutaneous lipomatosis (ECCL; Haberland syndrome, #613001) is an extremely rare congenital disorder that is manifested by the involvement of the skin, eyes and central nervous system (CNS). We report two cases of children with ECCL diagnosis. First was an 8-year-old girl who presented with symptomatic epilepsy, cerebral palsy and developmental delay. In 2020, she was admitted to the hospital due to the exacerbation of paresis and intensified prolonged epileptic seizures, provoked by infection of the middle ear. Diagnostic imaging revealed radiological changes suggestive of ECCL, providing a reason for the diagnosis, despite the lack of skin and eye anomalies. The second child, a 14-year-old girl, was consulted for subtle clinical signs and epilepsy suspicion. Diagnostic imaging findings were similar, though less pronounced. Based on neuroradiological abnormalities typical for Haberland syndrome, the authors discuss possible ECCL diagnosis.

Care4Rare Canada: Outcomes from a decade of network science for rare disease gene discovery

The past decade has witnessed a rapid evolution in rare disease (RD) research, fueled by the availability of genome-wide (exome and genome) sequencing. In 2011, as this transformative technology was introduced to the research community, the Care4Rare Canada Consortium was launched: initially as FORGE, followed by Care4Rare, and Care4Rare SOLVE. Over what amounted to three eras of diagnosis and discovery, the Care4Rare Consortium used exome sequencing and, more recently, genome and other 'omic technologies to identify the molecular cause of unsolved RDs. We achieved a diagnostic yield of 34% (623/1,806 of participating families), including the discovery of deleterious variants in 121 genes not previously associated with disease, and we continue to study candidate variants in novel genes for 145 families. The Consortium has made significant contributions to RD research, including development of platforms for data collection and sharing and instigating a Canadian network to catalyze functional characterization research of novel genes. The Consortium was instrumental to implementing genome-wide sequencing as a publicly funded test for RD diagnosis in Canada. Despite the successes of the past decade, the challenge of solving all RDs remains enormous, and the work is far from over. We must leverage clinical and 'omic data for secondary use, develop tools and policies to support safe data sharing, continue to explore the utility of new and emerging technologies, and optimize research protocols to delineate complex disease mechanisms. Successful approaches in each of these realms is required to offer diagnostic clarity to all families with RDs.

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.

A primary DICER1-sarcoma with KRAS and TP53 mutations in a child with suspected ECCL

A child had been followed since infancy by our multi-disciplinary neuro-oncology clinic with annual magnetic resonance imaging (MRI) under the presumed diagnosis of encephalocraniocutaneous lipomatosis (ECCL), with clinical features including nevus psiloliparus, scalp lipoma, nodular skin tag on and coloboma of the eyelid, cortical atrophy and meningeal angiomatosis. At the age of 4, she was found to have a large temporoparietal lesion causing elevated intracranial pressure requiring surgical resection. Histopathological exam of the tumor was suggestive of an intracranial sarcoma. Sequencing analysis of the tumor revealed mutations in DICER1, KRAS and TP53. Subsequent germline testing confirmed DICER1 syndrome and revealed an insignificant FGFR1 variant at a low frequency. Methylation profile of the tumor showed the tumor clustered most closely with sarcoma (rhabdomyosarcoma-like), confirming this tumor to be a primary DICER1-sarcoma. Compared to the previously reported cases, our unique case of primary DICER1-sarcoma also demonstrated neurofilament and chromogranin positivity, and genomic instability with loss of chromosome 4p, 4q, 8p, 11p, and 19p, as well as gains in chromosome 7p, 9p, 9q, 13q, and 15q on copy variant analysis. The detailed sequencing and methylation information discovered in this unique case of DICER1-sarcoma will hopefully help further our understanding of this rare and emerging entity.

Gremlin1 is a therapeutically targetable FGFR1 ligand that regulates lineage plasticity and castration resistance in prostate cancer

Among the greatest hurdles in clinical management of prostate cancer (PCa) are the progression to lethal castration-resistant prostate cancer (CRPC) and the lack of suitable targeted therapies for advanced disease. Here we identify Gremlin1 as a ligand for fibroblast growth factor receptor 1 (FGFR1), which promotes lineage plasticity and drives castration resistance. Importantly, we generate a specific anti-Gremlin1 therapeutic antibody and demonstrate synergistic effect with androgen deprivation therapy (ADT) in CRPC. GREM1 transcription is suppressed by androgen receptor (AR) and released following ADT. We show that Gremlin1 binds to FGFR1 and activates downstream MAPK signaling. Gremlin1 interacts with FGFR1 differently to its canonical ligand FGF1, as revealed through protein structure docking and mutagenesis experiments. Altogether, our data indicate Gremlin1 as a promising candidate therapeutic target for CRPC.

Toward clinical and molecular dissection of frontonasal dysplasia with facial skin polyps: From Pai syndrome to differential diagnosis through a series of 27 patients

Unique or multiple congenital facial skin polyps are features of several rare syndromes, from the most well-known Pai syndrome (PS), to the less recognized oculoauriculofrontonasal syndrome (OAFNS), encephalocraniocutaneous lipomatosis (ECCL), or Sakoda complex (SC). We set up a research project aiming to identify the molecular bases of PS. We reviewed 27 individuals presenting with a syndromic frontonasal polyp and initially referred for PS. Based on strict clinical classification criteria, we could confirm only nine (33%) typical and two (7%) atypical PS individuals. The remaining ones were either OAFNS (11/27-41%) or presenting with an overlapping syndrome (5/27-19%). Because of the phenotypic overlap between these entities, OAFNS, ECCL, and SC can be either considered as differential diagnosis of PS or part of the same spectrum. Exome and/or genome sequencing from blood DNA in 12 patients and from affected tissue in one patient failed to identify any replication in candidate genes. Taken together, our data suggest that conventional approaches routinely utilized for the identification of molecular etiologies responsible for Mendelian disorders are inconclusive. Future studies on affected tissues and multiomics studies will thus be required in order to address either the contribution of mosaic or noncoding variation in these diseases.

Mosaicism in Hartsfield syndrome

Hartsfield syndrome is a rare condition characterised by the co-occurrence of ectrodactyly and holoprosencephaly spectrum disorders; cleft lip and palate is a common associated feature. This is due to either monoallelic, or less commonly, biallelic variants in FGFR1 with a loss of function or dominant negative effect. To date 37 individuals have been reported, including two instances of germline mosaicism. We report a further family with Hartsfield syndrome due to a novel variant in FGFR1, with two affected fetuses, and somatic and germline mosaicism in the father detected on Sanger sequencing. The father had not come to medical attention prior to this finding. In light of our findings and those in the published literature, we suggest that mosaicism, either germline or germline and somatic, may be a relatively frequent finding, affecting 3 of 35 (9%) reported families, which has important implications for genetic counselling.

Expending the Phenotypic Spectrum of Encephalocraniocutaneous Lipomatosis: About a Prenatal Case With Complete Autopsy

Encephalocraniocutaneous lipomatosis (ECCL) or Haberland syndrome (MIM #613001) is a rare congenital neurocutaneous disorder. It is characterized by unilateral ocular, cutaneous and central nervous system anomalies. Key clinical features include hairless fatty tissue nevus of the scalp, choristoma of the eye and intraspinal and intracerebral lipomas. We report one of the first cases diagnosed after termination of pregnancy at 35 WG, including antenatal and post-mortem imaging, complete autopsy and genetic analysis. Prenatal ultrasound and MRI of the third trimester showed multifocal spinal lesions and left lateral cerebral ventriculomegaly with cerebral atrophy. Diagnosis of ECCL was suggested at complete autopsy which revealed nevus psiloliparus of the scalp, facial hamartomas and intracranial and spinal lipomas. In addition, our case also exhibited a cardiac rhabdomyoma and a multicystic dysplastic kidney, both never reported to date in this syndrome. ECCL was confirmed by the identification of a postzygotic FGFR1 mutation. We reviewed the literature and discuss the pathogenesis of this syndrome.

Encephalocraniocutaneous lipomatosıs (Haberland syndrome) in a newborn baby: a case report with review of literature

Encephalocraniocutaneous lipomatosis (ECCL) is an extremely uncommon, neurocutaneous disease, with a classical triad of ocular, skin lesions and central nervous system anomalies. We here report a case of ECCL in a newborn baby, characterized with naevus psiloliparus, choristoma, lipodermoids, cervical subcutaneous soft tissue mass, lowset ear, porencephalic cyst, polymicrogyria, arachnoid cyst, leptomeningeal angiomatosis and spinal lipomas. We here stress on the importance of early diagnosis to prevent misdiagnosis and employ a multidisciplinary approach in the management of these patients.

Somatic KRAS mutation affecting codon 146 in linear sebaceous nevus syndrome

Linear Sebaceous Nevus Syndrome is a rare disorder that presents with nevus sebaceus in association with corneal dermoids, colobomas, choroidal osteomas, and arachnoid cysts. It is thought to represent a mosaic RASopathy. These are disorders characterized by postzygotic somatic mutation in genes involved in RAS/MAPK signaling pathway. In this report we describe two patients with linear sebaceous nevus syndrome found to have mutations in codon 146 of KRAS with evidence of mosaicism. This specific mutation has previously been reported in Oculoectodermal Syndrome and Encephalocraniocutaneous Lipomatosis, two other mosaic RASopathies with predominantly cerebrooculocutaneous manifestations. These findings suggest that, while initially classified as different syndromes, these disorders should be evaluated and managed as a spectrum of related disorders.

Pathogenic postzygotic mosaicism in the tyrosine receptor kinase pathway: potential unidentified human disease hidden away in a few cells

Mutations occurring during embryonic development affect only a subset of cells resulting in two or more distinct cell populations that are present at different levels, also known as postzygotic mosaicism (PZM). Although PZM is a common biological phenomenon, it is often overlooked as a source of disease due to the challenges associated with its detection and characterization, especially for very low-frequency variants. Moreover, PZM can cause a different phenotype compared to constitutional mutations. Especially, lethal mutations in receptor tyrosine kinase (RTK) pathway genes, which exist only in a mosaic state, can have completely new clinical manifestations and can look very different from the associated monogenic disorder. However, some key questions are still not addressed, such as the level of mosaicism resulting in a pathogenic phenotype and how the clinical outcome changes with the development and age. Addressing these questions is not trivial as we require methods with the sensitivity to capture some of these variants hidden away in very few cells. Recent ultra-accurate deep-sequencing approaches can now identify these low-level mosaics and will be central to understand systemic and local effects of mosaicism in the RTK pathway. The main focus of this review is to highlight the importance of low-level mosaics and the need to include their detection in studies of genomic variation associated with disease.

Ophthalmic Manifestation and Pathological Features in a Cohort of Patients With Linear Nevus Sebaceous Syndrome and Encephalocraniocutaneous Lipomatosis

Purpose: This study aimed to figure out the association between ophthalmic and pathological features in patients with Linear Nevus Sebaceous Syndrome (LNSS) and in patients with Oculoectodermal Syndrome-Encephalocraniocutaneous Lipomatosis (OES-ECCL). Methods: It is a retrospective, non-consecutive, observational case series. Twenty-seven patients (12 with LNSS and 15 with OES-ECCL, 41 eyes) referred to the Department of Ophthalmology of the Shanghai Ninth People's Hospital between 2000 and 2020 were included. The mean age of the study population for the first-time consult was 5.7 years, ranging from 3 months to 34 years. Clinical notes, pathological records, and imaging findings were reviewed in all the patients. Results: Fourteen (51.9%) cases showed bilateral ocular involvement. Epibulbar choristomas were seen in all the patients. All the lesions involved the conjunctiva and cornea simultaneously. Multiple lesions were observed in 12 eyes. Of the 14 excised lesions, 11 were found to be complex choristomas. Further, 24 (89%) patients had eyelid coloboma. Also, 13 patients (48%) were diagnosed with strabismus, and 12 patients (44%) had abnormal fundus imaging, including optic nerve hypoplasia. Conclusions: LNSS and OES-ECCL shared common ophthalmic features, including epibulbar choristomas with distinctive characteristics, eyelid coloboma, strabismus, and optic nerve hypoplasia. The complex choristoma was found to be associated with the diseases. These specific patterns can be diagnostic clues to distinguish them from other syndromes, such as craniofacial defects, and to remind ophthalmologists that such patients require additional dermatological and neurological examinations and referral. Moreover, a thorough evaluation of ocular conditions is imperative for early interventions.

Fibrous Meningioma in a Patient with Encephalocraniocutaneous Lipomatosis: A Rare Case with Unique Features

Encephalocraniocutaneous lipomatosis “ECCL” is a rare, sporadic neurocutaneous disorder that results from a lethal autosomal mutation surviving by somatic mosaicism. It is characterized by unilateral involvement of skin, eyes and central nervous system in addition to a propensity for mesenchymal tumors. A 30-year-old male with previously controlled epilepsy presented with recurrent seizures. Brain imaging revealed a left parietal parasagittal enhancing tumor, in addition to left sided gyriform calcifications, and bilateral cerebral atrophy and ventricular dilatation more prominent on the left side. He also presented multiple left sided sebaceous nevi and abundant subcutaneous lipomas in addition to left mandibular condylar cysts. The brain tumor was excised, and cytopathology revealed a WHO grade I fibrous meningioma. After a thorough evaluation and exclusion of alternative diagnoses, the patient was diagnosed with definite encephalocraniocutaneous lipomatosis as per Moog’s criteria. Several cases of ECCL recently presented with different intracranial neoplasms. Here we report the first case of ECCL in association with meningioma.

Molecular markers and targeted therapy in pediatric low-grade glioma

INTRODUCTION

Recently discovered molecular alterations in pediatric low-grade glioma have helped to refine the classification of these tumors and offered novel targets for therapy. Genetic aberrations may combine with histopathology to offer new insights into glioma classification, gliomagenesis and prognosis. Therapies targeting common genetic aberrations in the MAPK pathway offer a novel mechanism of tumor control that is currently under study.

METHODS

We have reviewed common molecular alterations found in pediatric low-grade glioma as well as recent clinical trials of MEK and BRAF inhibitors.

RESULTS

In this topic review, we examine the current understanding of molecular alterations in pediatric low-grade glioma, as well as their role in diagnosis, prognosis and therapy. We summarize current data on the efficacy of targeted therapies in pediatric low-grade gliomas, as well as the many unanswered questions that these new discoveries and therapies raise.

CONCLUSIONS

The identification of driver alterations in pediatric low-grade glioma and the development of targeted therapies have opened new therapeutic avenues for patients with low-grade gliomas.

FGFR aberrations increase the risk of brain metastases and predict poor prognosis in metastatic breast cancer patients

Background:

The survival status of patients with breast cancer and brain metastasis (BCBM) receiving current treatments is poor.

Method:

We designed a real-world study to investigate using patients’ clinical and genetic aberrations to forecast the prognoses of BCBM patients. We recruited 146 BCBM patients and analyzed their clinical features to evaluate the overall survival (OS). For genetic testing, 30 BCBM and 165 non-brain-metastatic (BM) metastatic breast cancer (MBC) patients from Hunan Cancer Hospital, and 86 BCBM and 1416 non-BM MBC patients from the Geneplus database who received circulating tumor DNA testing, were compared and analyzed.

Results:

Ki67 >14% and >3 metastatic brain tumors were significant risk factors associated with poor OS, while chemotherapy and brain radiotherapy were beneficial factors for better OS. Compared with non-BM MBC patients, BCBM patients had more fibroblast growth factor receptor (FGFR) aberrations. The combination of FGFR, TP53 and FLT1 aberrations plus immunohistochemistry HER2-positive were associated with an increased risk of brain metastasis (AUC = 77.13%). FGFR aberration alone was not only a predictive factor (AUC = 67.90%), but also a significant risk factor for poor progression-free survival (Logrank p = 0.029). FGFR1 aberration was more frequent than other FGFR family genes in BCBM patients, and FGFR1 aberration was significantly higher in BCBM patients than non-BM MBC patients. Most FGFR1-amplified MBC patients progressed within 3 months of the late-line (>2 lines) treatment.

Conclusion:

A group of genetic events, including FGFR, TP53 and FLT1 genetic aberrations, and HER2-positivity, forecasted the occurrence of BM in breast cancers. FGFR genetic aberration alone predicted poor prognosis.

Disorders Caused by Genetic Mosaicism

BACKGROUND

Genetic mosaics arise through new mutations occurring after fertiliza- tion (i.e., postzygotic mutations). Mosaics have been described in recent years as the cause of many different disorders; many of these are neurocutaneous diseases and syndromal developmental disorders, each with a characteristic phenotype. In some of these disorders, there is a genetic predisposition to the development of tumors. This article is intended as an overview of selected mosaic diseases.

METHODS

This review is based on publications retrieved by a selective search in PubMed, with particular attention to recent articles in high-ranking journals dealing with asymmetric growth disturbances, focal brain malformations, mosaic diseases due to dysregulation of the RAS/RAF signaling pathway (mosaic RASopathies), and vascular malformations.

RESULTS

The identification of postzygotic mutations has led to the reclassification of traditional disease entities and to a better understanding of their pathogenesis. Diagnosis is aided by modern next-generation sequencing (NGS) techniques that allow the detection even of low-grade mosaics. Many mosaic mutations are not detectable in blood, but only in the affected tissue, e.g., the skin. Genetic mosaic diseases often manifest themselves in the skin and brain, and by facial dysmorphism, asymmetrical growth disturbances, and vascular malformations.

CONCLUSION

The possibility of a mosaic disease should be kept in mind in the diag- nostic evaluation of patients with asymmetrical growth disturbances, focal neuronal migration disturbances, vascular malformations, and linear skin abnormalities. The demonstration of a postzygotic mutation often affords relief to the parents of an affected child, since this means that there is no increased risk for recurrence of the same disorder in future children. Correct classification is important, as molecular available for certain mosaic diseases, e.g., PIK3CA-related overgrowth spectrum (PROS) disorder.

FGFR- gene family alterations in low-grade neuroepithelial tumors

The discovery of fibroblast growth factor receptor (FGFR) gene family alterations as drivers of primary brain tumors has generated significant excitement, both as potential therapeutic targets as well as defining hallmarks of histologic entities. However, FGFR alterations among neuroepithelial lesions are not restricted to high or low grade, nor to adult vs. pediatric-type tumors. While it may be tempting to consider FGFR-altered tumors as a unified group, this underlying heterogeneity poses diagnostic and interpretive challenges. Therefore, understanding the underlying biology of tumors harboring specific FGFR alterations is critical. In this review, recent evidence for recurrent FGFR alterations in histologically and biologically low-grade neuroepithelial tumors (LGNTs) is examined (namely FGFR1 tyrosine kinase domain duplication in low grade glioma, FGFR1-TACC1 fusions in extraventricular neurocytoma [EVN], and FGFR2-CTNNA3 fusions in polymorphous low-grade neuroepithelial tumor of the young [PLNTY]). Additionally, FGFR alterations with less well-defined prognostic implications are considered (FGFR3-TACC3 fusions, FGFR1 hotspot mutations). Finally, a framework for practical interpretation of FGFR alterations in low grade glial/glioneuronal tumors is proposed.

FGFR- gene family alterations in low-grade neuroepithelial tumors

The discovery of fibroblast growth factor receptor (FGFR) gene family alterations as drivers of primary brain tumors has generated significant excitement, both as potential therapeutic targets as well as defining hallmarks of histologic entities. However, FGFR alterations among neuroepithelial lesions are not restricted to high or low grade, nor to adult vs. pediatric-type tumors. While it may be tempting to consider FGFR-altered tumors as a unified group, this underlying heterogeneity poses diagnostic and interpretive challenges. Therefore, understanding the underlying biology of tumors harboring specific FGFR alterations is critical. In this review, recent evidence for recurrent FGFR alterations in histologically and biologically low-grade neuroepithelial tumors (LGNTs) is examined (namely FGFR1 tyrosine kinase domain duplication in low grade glioma, FGFR1-TACC1 fusions in extraventricular neurocytoma [EVN], and FGFR2-CTNNA3 fusions in polymorphous low-grade neuroepithelial tumor of the young [PLNTY]). Additionally, FGFR alterations with less well-defined prognostic implications are considered (FGFR3-TACC3 fusions, FGFR1 hotspot mutations). Finally, a framework for practical interpretation of FGFR alterations in low grade glial/glioneuronal tumors is proposed.

Nevus psiloliparus: Newly described histopathological features from transverse sections

Nevus psiloliparus is a rare fatty tissue nevus that is a marker for encephalocraniocutaneous lipomatosis, a neurocutaneous syndrome with ocular and central nervous system anomalies. Clinically, nevus psiloliparus is often described as a congenital alopecia and appears as an irregularly shaped, circumscribed area of alopecia on the scalp. Histopathology demonstrates a near-complete absence of mature hair follicles with preservation of arrector pili muscles and mature adipocytes within the dermis. The pathogenesis of nevus psiloliparus may be related to mosaic mutations in fibroblast growth factor receptor 1. Herein we report the histopathological features of a nevus psiloliparus in an 11-year-old girl diagnosed from transverse sections, which show "shadow" follicular units characterized by columns of loosely arranged collagen and a relative paucity of elastic fibers.

GnRH Deficient Patients With Congenital Hypogonadotropic Hypogonadism: Novel Genetic Findings in ANOS1, RNF216, WDR11, FGFR1, CHD7, and POLR3A Genes in a Case Series and Review of the Literature

Background: Congenital hypogonadotropic hypogonadism (CHH) is a rare genetic disease caused by Gonadotropin-Releasing Hormone (GnRH) deficiency. So far a limited number of variants in several genes have been associated with the pathogenesis of the disease. In this original research and review manuscript the retrospective analysis of known variants in ANOS1 (KAL1), RNF216, WDR11, FGFR1, CHD7, and POLR3A genes is described, along with novel variants identified in patients with CHH by the present study. Methods: Seven GnRH deficient unrelated Cypriot patients underwent whole exome sequencing (WES) by Next Generation Sequencing (NGS). The identified novel variants were initially examined by in silico computational algorithms and structural analysis of their predicted pathogenicity at the protein level was confirmed. Results: In four non-related GnRH males, a novel X-linked pathogenic variant in ANOS1 gene, two novel autosomal dominant (AD) probably pathogenic variants in WDR11 and FGFR1 genes and one rare AD probably pathogenic variant in CHD7 gene were identified. A rare autosomal recessive (AR) variant in the SRA1 gene was identified in homozygosity in a female patient, whilst two other male patients were also, respectively, found to carry novel or previously reported rare pathogenic variants in more than one genes; FGFR1/POLR3A and SRA1/RNF216. Conclusion: This report embraces the description of novel and previously reported rare pathogenic variants in a series of genes known to be implicated in the biological development of CHH. Notably, patients with CHH can harbor pathogenic rare variants in more than one gene which raises the hypothesis of locus-locus interactions providing evidence for digenic inheritance. The identification of such aberrations by NGS can be very informative for the management and future planning of these patients.

An update on oculocerebrocutaneous (Delleman-Oorthuys) syndrome

Oculocerebrocutaneous syndrome (OCCS) is a rare disorder characterized primarily by congenital skin, eye, and brain anomalies. The most distinctive findings are hypoplastic or aplastic skin defects; pedunculated, typically hamartomatous, or nodular skin appendages; cystic microphthalmia; and a combination of forebrain anomalies and a specific mid-hindbrain malformation. Based on a review of 40 patients with OCCS, existing clinical criteria have been revised. Because of the asymmetric and patchy distribution of features, lack of recurrence in families, male preponderance and completely skewed X-inactivation in one female, OCCS is hypothesized to result from postzygotic mosaic variants in an X-linked gene. Whole exome and genome sequencing on blood DNA in two patients failed to identify pathogenic variants so far. In view of the overlapping features, in particular of the brain, of OCCS and Aicardi syndrome, both may be pathogenetically related or even result from different variants in the same gene. For the elucidation of the cause of OCCS, exome or genome sequencing on multiple lesional tissues is the primary goal.

Genotype correlates with clinical severity in PIK3CA-associated lymphatic malformations

Lymphatic malformations (LMs) are congenital, nonneoplastic vascular malformations associated with postzygotic activating PIK3CA mutations. The mutation spectrum within LMs is narrow, with the majority having 1 of 3 hotspot mutations. Despite this relative genetic homogeneity, clinical presentations differ dramatically. We used molecular inversion probes and droplet digital polymerase chain reaction to perform deep, targeted sequencing of PIK3CA in 271 affected and unaffected tissue samples from 81 individuals with isolated LMs and retrospectively collected clinical data. Pathogenic PIK3CA mutations were identified in affected LM tissue in 64 individuals (79%) with isolated LMs, with variant allele fractions (VAFs) ranging from 0.1% to 13%. Initial analyses revealed no correlation between VAF and phenotype variables. Recognizing that different mutations activate PI3K to varying degrees, we developed a metric, the genotype-adjusted VAF (GVAF), to account for differences in mutation strength, and found significantly higher GVAFs in LMs with more severe clinical characteristics including orofacial location or microcystic structure. In addition to providing insight into LM pathogenesis, we believe GVAF may have broad applicability for genotype-phenotype analyses in mosaic disorders.

Giant Ocular Lipodermoid Cyst in Encephalocraniocutaneous Lipomatosis: Surgical Treatment and Genetic Analysis

BACKGROUND Encephalocraniocutaneous lipomatosis is a rare neurocutaneous disorder characterized by cutaneous, ocular, and central nervous system anomalies; its molecular etiology was recently identified. This report describes the surgical treatment and genetic characterization of a giant ocular lipodermoid cyst secondary to encephalocraniocutaneous lipomatosis. CASE REPORT An 11-year-old girl with past medical history of absence seizures presented with a reddish protruding mass in her right eye involving the temporal conjunctiva and the peripheral temporal cornea; eyelid closure was not possible due to mass protrusion. She also presented skin tags at the level of the external canthus and 3 alopecic areas at the level of the scalp compatible with nevus psiloliparus. No family history was reported. A dermoid cyst was suspected and excisional biopsy was performed under general anesthesia. A large conjunctival and lamellar corneoscleral resection was done, followed by a corneal tectonic graft. Molecular analysis was carried out, including PCR and Sanger sequencing on DNA obtained from the mass. After surgery, the patient achieved complete eyelid closure, reduction of ocular surface symptoms, and improved aesthetic appearance. Histological analysis confirmed a lipodermoid cyst; genetic tests confirmed a mosaic activating mutation in FGFR1 (c.1638C>A, p.Asn546Lys). The diagnosis was encephalocraniocutaneous lipomatosis. CONCLUSIONS ECCL is a rare condition; an accurate diagnosis comprising clinical and genetic aspects can facilitate the monitoring of possible complications, improve the multidisciplinary treatment, and provide valuable information for future therapy developments. In this case, the patient's quality of life improved significantly, ocular symptoms disappeared, and a good esthetic appearance was achieved.

Novel synonymous and missense variants in FGFR1 causing Hartsfield syndrome

Hartsfield syndrome is a rare clinical entity characterized by holoprosencephaly and ectrodactyly with the variable feature of cleft lip/palate. In addition to these symptoms patients with Hartsfield syndrome can show developmental delay of variable severity, isolated hypogonadotropic hypogonadism, central diabetes insipidus, vertebral anomalies, eye anomalies, and cardiac malformations. Pathogenic variants in FGFR1 have been described to cause phenotypically different FGFR1-related disorders such as Hartsfield syndrome, hypogonadotropic hypogonadism with or without anosmia, Jackson-Weiss syndrome, osteoglophonic dysplasia, Pfeiffer syndrome, and trigonocephaly Type 1. Here, we report three patients with Hartsfield syndrome from two unrelated families. Exome sequencing revealed two siblings harboring a novel de novo heterozygous synonymous variant c.1029G>A, p.Ala343Ala causing a cryptic splice donor site in exon 8 of FGFR1 likely due to gonadal mosaicism in one parent. The third case was a sporadic patient with a novel de novo heterozygous missense variant c.1868A>G, p.(Asp623Gly).

FGFR1 Mosaic Pathogenic Variant in Encephalocraniocutaneous Lipomatosis with Leptomeningeal Angiomatosis

Encephalocraniocutaneous lipomatosis (ECCL) is a congenital neurocutaneous disorder. It is characterized by ocular anomalies (epibulbar choristomas), skin lesions (as nevus psiloliparus and subcutaneous lipomas), and central nervous system abnormalities (mostly arachnoid cysts, brain anomalies, vascular defects, and intracranial and spinal lipomas). Mutations in KRAS and fibroblast growth factor receptor gene-1 (FGFR1) are related to ECCL, explaining additional manifestations such as jaw tumors or gliomas. We report a pediatric patient with clinical, radiological, and histological findings consistent with ECCL and a mosaic pathogenic variant in FGFR1 found in the DNA from a non-cultured biopsy of the nevus psiloliparus and absent in blood and DNA from buccal mucosa.

What's New in Genetic Skin Diseases

The discoveries of new genes underlying genetic skin diseases have occurred at a rapid pace, supported by advances in DNA sequencing technologies. These discoveries have translated to an improved understanding of disease mechanisms at a molecular level and identified new therapeutic options based on molecular targets. This article highlights just a few of these recent discoveries for a diverse group of skin diseases, including tuberous sclerosis complex, ichthyoses, overgrowth syndromes, interferonopathies, and basal cell nevus syndrome, and how this has translated into novel targeted therapies and improved patient care.

Sensitive detection of FGFR1 N546K mosaic mutation in patient with encephalocraniocutaneous lipomatosis and pilocytic astrocytoma

Encephalocraniocutaneous lipomatosis (ECCL) is a rare neurocutaneous disorder, with only about 100 cases reported worldwide. It is characterized by congenital lesions of the eye, skin, and central nervous system. Only recently, potential causative FGFR1 point mutations have been identified in brain tumors and cultured skin biopsies from patients with this condition. Here, we analyzed the molecular status of a patient with ECCL and a coexisting pilocytic astrocytoma with detected FGFR1 N546K mutation. The presence of the alteration in both affected and unaffected tissues has been evaluated using Sanger sequencing and droplet digital polymerase chain reaction (ddPCR) technique. The ddPCR analysis showed differential distribution of the alteration in all specimens, including unaffected and untreated samples. Therefore, we confirm that FGFR1 N546K is a plausible causative mutation of ECCL patients and could be associated with a risk of brain tumor development. We also show the usefulness of sensitive ddPCR method for detection of low levels of autosomal mosaic mutation in blood or swabs. We suggest that utilization of this method may improve the diagnostic process, especially when targeted therapies are considered.

Expansion of the phenotypic spectrum and description of molecular findings in a cohort of patients with oculocutaneous mosaic RASopathies

BACKGROUND

Postzygotic KRAS, HRAS, NRAS, and FGFR1 mutations result in a group of mosaic RASopathies characterized by related developmental anomalies in eye, skin, heart, and brain. These oculocutaneous disorders include oculoectodermal syndrome (OES) encephalo-cranio-cutaneous lipomatosis (ECCL), and Schimmelpenning-Feuerstein-Mims syndrome (SFMS). Here, we report the results of the clinical and molecular characterization of a novel cohort of patients with oculocutaneous mosaic RASopathies.

METHODS

Two OES, two ECCL, and two SFMS patients were ascertained in the study. In addition, two subjects with unilateral isolated epibulbar dermoids were also enrolled. Molecular analysis included PCR amplification and Sanger sequencing of KRAS, HRAS, NRAS, and FGFR1 genes in DNA obtained from biopsies (skin/epibulbar dermoids), buccal mucosa, and blood leukocytes. Massive parallel sequencing was employed in two cases with low-level mosaicism.

RESULTS

In DNA from biopsies, mosaicism for pathogenic variants, including KRAS p.Ala146Thr in two OES subjects, FGFR1 p.Asn546Lys and KRAS p.Ala146Val in ECCL patients, and KRAS p.Gly12Asp in both SFMS patients, was demonstrated. No mutations were shown in DNA from conjunctival lesions in two subjects with isolated epibubar dermoids.

CONCLUSION

Our study allowed the expansion of the clinical spectrum of mosaic RASopathies and supports that mosaicism for recurrent mutations in KRAS and FGFR1 is a commonly involved mechanism in these rare oculocutaneous anomalies.

Adipocytic tumors in Children: A contemporary review

Adipocytic neoplasms in the pediatric population demonstrate a different histologic spectrum and frequency than in adults. The vast majority of these tumors are benign, with lipoma being the most common entity. The identification of signature cytogenetic and molecular alterations for certain lesions, such as PLAG1 gene rearrangement in lipoblastoma and FUS-DDIT3 fusion in myxoid liposarcoma, has been helpful in approaching these neoplasms and aiding in confirming the diagnosis. Furthermore, it is important for pathologists to recognize that adipocytic neoplasms may be associated with different syndromes with potential impact in managing such patients. This review provides a summary of the clinical pictures, histologic characteristics, molecular alterations, differential diagnoses, and syndromic associations of the commonly encountered fatty tumors in children.

A novel dominant-negative FGFR1 variant causes Hartsfield syndrome by deregulating RAS/ERK1/2 pathway

Hartsfield syndrome (HS) is an ultrarare developmental disorder mainly featuring holoprosencephaly and ectrodactyly. It is caused by heterozygous or biallelic variants in FGFR1. Recently, a dominant-negative effect was suggested for FGFR1 variants associated with HS. Here, exome sequencing analysis in a 12-year-old boy with HS disclosed a novel de novo heterozygous variant c.1934C>T in FGFR1 predicted to cause the p.(Ala645Val) amino-acid substitution. In order to evaluate whether the variant, changing a highly conserved residue of the kinase domain, affects FGFR1 function, biochemical studies were employed. We measured the FGFR1 receptor activity in FGF2-treated cell lines exogenously expressing wild-type or Ala645Val FGFR1 by monitoring the activation status of FGF2/FGFR1 downstream pathways. Our analysis highlighted that RAS/ERK1/2 signaling was significantly perturbed in cells expressing mutated FGFR1, in comparison with control cells. We also provided preliminary evidence showing a modulation of the autophagic process in cells expressing mutated FGFR1. This study expands the FGFR1 mutational spectrum associated with HS, provides functional evidence further supporting a dominant-negative effect of this category of FGFR1 variants and offers initial insights on dysregulation of autophagy in HS.

The oculoauriculofrontonasal syndrome: Further clinical characterization and additional evidence suggesting a nontraditional mode of inheritance

The oculoauriculofrontonasal syndrome (OAFNS) is a rare disorder characterized by the association of frontonasal dysplasia (widely spaced eyes, facial cleft, and nose abnormalities) and oculo-auriculo-vertebral spectrum (OAVS)-associated features, such as preauricular ear tags, ear dysplasia, mandibular asymmetry, epibulbar dermoids, eyelid coloboma, and costovertebral anomalies. The etiology is unknown so far. This work aimed to identify molecular bases for the OAFNS. Among a cohort of 130 patients with frontonasal dysplasia, accurate phenotyping identified 18 individuals with OAFNS. We describe their clinical spectrum, including the report of new features (micro/anophtalmia, cataract, thyroid agenesis, polymicrogyria, olfactory bulb hypoplasia, and mandibular cleft), and emphasize the high frequency of nasal polyps in OAFNS (56%). We report the negative results of ALX1, ALX3, and ALX4 genes sequencing and next-generation sequencing strategy performed on blood-derived DNA from respectively, four and four individuals. Exome sequencing was performed in four individuals, genome sequencing in one patient with negative exome sequencing result. Based on the data from this series and the literature, diverse hypotheses can be raised regarding the etiology of OAFNS: mosaic mutation, epigenetic anomaly, oligogenism, or nongenetic cause. In conclusion, this series represents further clinical delineation work of the rare OAFNS, and paves the way toward the identification of the causing mechanism.

The Rare Neurocutaneous Disorders: Update on Clinical, Molecular, and Neuroimaging Features

Phakomatoses, also known as neurocutaneous disorders, comprise a vast number of entities that predominantly affect structures originated from the ectoderm such as the central nervous system and the skin, but also the mesoderm, particularly the vascular system. Extensive literature exists about the most common phakomatoses, namely neurofibromatosis, tuberous sclerosis, von Hippel-Lindau and Sturge-Weber syndrome. However, recent developments in the understanding of the molecular underpinnings of less common phakomatoses have sparked interest in these disorders. In this article, we review the clinical features, current pathogenesis, and modern neuroimaging findings of melanophakomatoses, vascular phakomatoses, and other rare neurocutaneous syndromes that may also include tissue overgrowth or neoplastic predisposition.