Biomarker Landscape in RASopathies.

RASopathies are a group of related genetic disorders caused by mutations in genes within the RAS/MAPK signaling pathway. This pathway is crucial for cell division, growth, and differentiation, and its disruption can lead to a variety of developmental and health issues. RASopathies present diverse clinical features and pose significant diagnostic and therapeutic challenges. Studying the landscape of biomarkers in RASopathies has the potential to improve both clinical practices and the understanding of these disorders. This review provides an overview of recent discoveries in RASopathy molecular profiling, which extend beyond traditional gene mutation analysis. mRNAs, non-coding RNAs, protein expression patterns, and post-translational modifications characteristic of RASopathy patients within pivotal signaling pathways such as the RAS/MAPK, PI3K/AKT/mTOR, and Rho/ROCK/LIMK2/cofilin pathways are summarized. Additionally, the field of metabolomics holds potential for uncovering metabolic signatures associated with specific RASopathies, which are crucial for developing precision medicine. Beyond molecular markers, we also examine the role of histological characteristics and non-invasive physiological assessments in identifying potential biomarkers, as they provide evidence of the disease's effects on various systems. Here, we synthesize key findings and illuminate promising avenues for future research in RASopathy biomarker discovery, underscoring rigorous validation and clinical translation.

Pathogenic variants in KMT2C result in a neurodevelopmental disorder distinct from Kleefstra and Kabuki syndromes.

Trithorax-related H3K4 methyltransferases, KMT2C and KMT2D, are critical epigenetic modifiers. Haploinsufficiency of KMT2C was only recently recognized as a cause of neurodevelopmental disorder (NDD), so the clinical and molecular spectrums of the KMT2C-related NDD (now designated as Kleefstra syndrome 2) are largely unknown. We ascertained 98 individuals with rare KMT2C variants, including 75 with protein-truncating variants (PTVs). Notably, ∼15% of KMT2C PTVs were inherited. Although the most highly expressed KMT2C transcript consists of only the last four exons, pathogenic PTVs were found in almost all the exons of this large gene. KMT2C variant interpretation can be challenging due to segmental duplications and clonal hematopoesis-induced artifacts. Using samples from 27 affected individuals, divided into discovery and validation cohorts, we generated a moderate strength disorder-specific KMT2C DNA methylation (DNAm) signature and demonstrate its utility in classifying non-truncating variants. Based on 81 individuals with pathogenic/likely pathogenic variants, we demonstrate that the KMT2C-related NDD is characterized by developmental delay, intellectual disability, behavioral and psychiatric problems, hypotonia, seizures, short stature, and other comorbidities. The facial module of PhenoScore, applied to photographs of 34 affected individuals, reveals that the KMT2C-related facial gestalt is significantly different from the general NDD population. Finally, using PhenoScore and DNAm signatures, we demonstrate that the KMT2C-related NDD is clinically and epigenetically distinct from Kleefstra and Kabuki syndromes. Overall, we define the clinical features, molecular spectrum, and DNAm signature of the KMT2C-related NDD and demonstrate they are distinct from Kleefstra and Kabuki syndromes highlighting the need to rename this condition.

Dermatological manifestations in Costello syndrome: A prospective multicentric study of 31 HRAS-positive variant patients.

BACKGROUND: Data on dermatological manifestations of Costello syndrome (CS) remain heterogeneous and lack in validated description. OBJECTIVES: To describe the dermatological manifestations of CS; compare them with the literature findings; assess those discriminating CS from other RASopathies, including cardiofaciocutaneous syndrome (CFCS) and the main types of Noonan syndrome (NS); and test for dermatological phenotype-genotype correlations. METHODS: We performed a 10-year, large, prospective, multicentric, collaborative dermatological and genetic study. RESULTS: Thirty-one patients were enrolled. Hair abnormalities were ubiquitous, including wavy or curly hair and excessive eyebrows, respectively in 68% and 56%. Acral excessive skin (AES), papillomas and keratotic papules (PKP), acanthosis nigricans (AN), palmoplantar hyperkeratosis (PPHK) and 'cobblestone' papillomatous papules of the upper lip (CPPUL), were noted respectively in 84%, 61%, 65%, 55% and 32%. Excessive eyebrows, PKP, AN, CCPUL and AES best differentiated CS from CFCS and NS. Multiple melanocytic naevi (>50) may constitute a new marker of attenuated CS associated with intragenic duplication in HRAS. Oral acitretin may be highly beneficial for therapeutic management of PPHK. No significant dermatological phenotype-genotype correlation was determined between patients with and without HRAS c.34G>A (p.G12S). CONCLUSIONS AND RELEVANCE: This validated phenotypic characterization of a large number of patients with CS will allow future researchers to make a positive diagnosis, and to differentiate CS from CFCS and NS.

Autism spectrum disorder profiles in RASopathies: A systematic review.

BACKGROUND: RASopathies are associated with an increased risk of autism spectrum disorder (ASD). For neurofibromatosis type 1 (NF1) there is ample evidence for this increased risk, while for other RASopathies this association has been studied less. No specific ASD profile has been delineated so far for RASopathies or a specific RASopathy individually. METHODS: We conducted a systematic review to investigate whether a specific RASopathy is associated with a specific ASD profile, or if RASopathies altogether have a distinct ASD profile compared to idiopathic ASD (iASD). We searched PubMed, Web of Science, and Open Grey for data about ASD features in RASopathies and potential modifiers. RESULTS: We included 41 articles on ASD features in NF1, Noonan syndrome (NS), Costello syndrome (CS), and cardio-facio-cutaneous syndrome (CFC). Individuals with NF1, NS, CS, and CFC on average have higher ASD symptomatology than healthy controls and unaffected siblings, though less than people with iASD. There is insufficient evidence for a distinct ASD phenotype in RASopathies compared to iASD or when RASopathies are compared with each other. We identified several potentially modifying factors of ASD symptoms in RASopathies. CONCLUSIONS: Our systematic review found no convincing evidence for a specific ASD profile in RASopathies compared to iASD, or in a specific RASopathy compared to other RASopathies. However, we identified important limitations in the research literature which may also account for this result. These limitations are discussed and recommendations for future research are formulated.

Clinical details of individuals with Rauch-Steindl syndrome due to NSD2 truncating variants.

BACKGROUND: Rauch-Steindl syndrome (RAUST) is a very rare genetic syndrome caused by a pathogenic variant in NSD2 on chromosome 4p16.3. Although NSD2 was previously thought to be the major gene in Wolf-Hirschhorn syndrome (WHS), a contiguous gene syndrome of chromosome 4p16.3 deletion, RAUST has been found to present different facial and clinical features from WHS. In this study, we report the details of two newly diagnosed individuals with RAUST in order to better understand the molecular and clinical features of RAUST. METHODS: Whole-genome sequencing was performed on two individuals with psychomotor delay and growth failure. Detailed clinical evaluation of growth parameters, craniofacial features, electroencephalogram (EEG), magnetic resonance imaging of the brain, and developmental assessment were performed. RESULTS: Both individuals had de novo truncating variants in NSD2. One had a novel variant (c.2470C>T, p.Arg824*), and the other had a recurrent variant (c.4028del, p.Pro1343Glnfs*49). Both exhibited characteristic RAUST facial features, growth failure, and mild psychomotor delay. A novel finding of RAUST was seen in individual 2, a Chiari malformation type 1, and both showed delayed bone age. They lacked common WHS features such as congenital heart defects, cleft lip/palate, and seizures (EEG with abnormal findings). CONCLUSION: We present a novel variant and clinical presentations of RAUST, expand the molecular and clinical diversity of RAUST, and improve our understanding of this rare syndrome, which is distinct from WHS. Further researches are needed on more RAUST cases and on functional analysis of NSD2.

Grb7 knockout mice develop normally but litters born to knockout females fail to thrive.

BACKGROUND: Growth factor receptor-bound 7 (Grb7) is an adaptor protein involved in signal transduction downstream of multiple receptor tyrosine kinases, including ERBB, FGFR, and PDGFR pathways. Experimental studies have implicated Grb7 in regulating cell proliferation, survival, migration, and invasion through its large repertoire of protein-protein interactions. RESULTS: Here, we describe the generation and characterization of a Grb7 knockout mouse. These mice are viable and fertile. A lacZ knock-in reporter was used to visualize Grb7 promoter activity patterns in adult tissues, indicating widespread Grb7 expression in glandular epithelium, the central nervous system, and other tissues. The sole defect observed in these animals was a failure of Grb7 knockout females to successfully raise pups to weaning age, a phenotype that was independent of both paternal and pup genotypes. CONCLUSIONS: These data suggest a regulatory role for Grb7 in mammary lactational physiology.

Heterozygous gain of function variants in a critical region of RNF13 cause congenital microcephaly, epileptic encephalopathy, blindness, and failure to thrive.

Missense variants in the RNF13 gene have been previously known to cause congenital microcephaly, epileptic encephalopathy, blindness, and failure to thrive through a gain-of-function disease mechanism. Here, we identify a nonsense variant, expected to result in protein truncation, in a similarly affected patient. We show that this nonsense variant, residing in the terminal exon, is likely to escape nonsense-mediated decay while removing a critical region for protein function, thus resulting in a gain-of-function effect. We review the literature and disease databases and identify several other affected individuals with overlapping phenotypes carrying distinct truncating variants in the terminal exon upstream of the putative critical region. Furthermore, we analyze truncating variants from the general population, namely, the Genome Aggregation Database (gnomAD), and provide additional evidence supporting our hypothesis, and ruling out haploinsufficiency as an alternative disease mechanism. In summary, our case report, literature review, and analysis of disease and population databases strongly support the hypothesis that heterozygous gain-of-function variants in a critical region of RNF13 cause congenital microcephaly, epileptic encephalopathy, blindness, and failure to thrive.

A very mild phenotype in six individuals of a three-generation family with the novel HRAS variant c.176C > G p.(Ala59Gly): Emergence of a new HRAS-related RASopathy distinct from Costello syndrome.

Costello syndrome is a clinically recognizable, severe neurodevelopmental disorder caused by heterozygous activating variants in HRAS. The vast majority of affected patients share recurring variants affecting HRAS codons 12 and 13 and a relatively uniform phenotype. Here, we report the unique and attenuated phenotype of six individuals of an extended family affected by the HRAS variant c.176C>T p.(Ala59Gly), which, to our knowledge, has never been reported as a germline variant in patients so far. HRAS Alanine 59 has been previously functionally investigated as an oncogenic hotspot and the p.Ala59Gly substitution was shown to impair intrinsic GTP hydrolysis. All six individuals we report share a phenotype of ectodermal anomalies and mild features suggestive of a RASopathy, reminiscent of patients with Noonan syndrome-like disorder with loose anagen hair. All six are of normal intelligence, none have a history of failure to thrive or malignancy, and they have no known cardiac or neurologic pathologies. Our report adds to the previous reports of patients with rare variants affecting amino acids located in the SWITCH II/G3 region of HRAS and suggests a consistent, attenuated phenotype distinct from classical Costello syndrome. We propose the definition of a new distinct HRAS-related RASopathy for patients carrying HRAS variants affecting codons 58, 59, 60.

Phenotypic variability and gastrointestinal manifestations/interventions for growth in NAA10-related neurodevelopmental syndrome.

Our study of 61 children with NAA10-related neurodevelopmental syndrome, an X-linked disorder due to NAA10 gene variants, demonstrated a high prevalence of growth failure, with weight and height percentiles often in the failure-to-thrive diagnostic range; however, dramatic weight fluctuations and phenotypic variability is evidenced in the growth parameters of this population. Although never previously explored in depth, the gastrointestinal pathology associated with NAA10-related neurodevelopmental syndrome includes feeding difficulties in infancy, dysphagia, GERD/silent reflux, vomiting, constipation, diarrhea, bowel incontinence, and presence of eosinophils on esophageal endoscopy, in order from most to least prevalent. Additionally, the gastrointestinal symptom profile for children with this syndrome has been expanded to include eosinophilic esophagitis, cyclic vomiting syndrome, Mallory Weiss tears, abdominal migraine, esophageal dilation, and subglottic stenosis. Although the exact cause of poor growth in NAA10-related neurodevelopmental syndrome probands is unclear and the degree of contribution to this problem by GI symptomatology remains uncertain, an analysis including nine G-tube or GJ-tube fed probands demonstrates that G/GJ-tubes are overall efficacious with respect to improvements in weight gain and caregiving. The choice to insert a gastrostomy or gastrojejunal tube to aid with weight gain is often a challenging decision to make for parents, who may alternatively choose to rely on oral feeding, caloric supplementation, calorie tracking, and feeding therapy. In this case, if NAA10-related neurodevelopmental syndrome children are not tracking above the failure to thrive (FTT) range past 1 year of age despite such efforts, the treating physicians should be consulted regarding possibly undergoing G-tube placement to avoid prolonged growth failure. If G-tubes are not immediately inducing weight gain after insertion, recommendations could include altering formula, increasing caloric input, or exchanging a G-tube for a GJ-tube by means of a minimally invasive procedure.

Mutación DGAT1 en dos hermanas con falla de medro: reporte de caso / DGAT1 mutation in two sisters with failure to thrive: a case report

Las diarreas y enteropatías congénitas (CODE por su sigla en inglés) son un grupo de trastornos monogénicos que se han descrito en los últimos años. Dentro de las CODE, la mutación del gen de la diacilglicerol o-aciltransferasa 1 (DGAT1) es un trastorno enzimático poco común asociado con diarrea crónica grave de aparición temprana. El objetivo es presentar a dos hermanas que consultaron por diarrea crónica, retraso en el crecimiento, vómitos e hipoalbuminemia en la primera infancia. En ambas pacientes se encontró un compuesto heterocigota de la mutación del DGAT1. Esta mutación se describió previamente en la población asiática; sin embargo, estas son las dos primeras pacientes en tener esta mutación en la población latinoamericana. Estos dos casos pueden ampliar nuestro conocimiento sobre las diarreas congénitas en general y las características clínicas de los pacientes con mutaciones en DGAT1 en particular.

Congenital diarrhea and enteropathies (CODEs) are a group of monogenic disorders that have been described in recent years. Within the CODEs, the mutation in the diacylglycerol O-acyltransferase 1 (DGAT1) gene is a rare enzyme disorder associated with severe, early-onset chronic diarrhea. Our objective is to describe the case of 2 sisters who consulted for chronic diarrhea, growth retardation, vomiting, and hypoalbuminemia in early childhood. A compound heterozygous DGAT1 mutation was found in both patients. This mutation was previously described in the Asian population; however, these are the first 2 patients to show this mutation in the Latin American population. These 2 cases may expand our knowledge about congenital diarrhea in general and the clinical characteristics of patients with DGAT1 mutations in particular.

An Assessment of the Therapeutic Landscape for the Treatment of Heart Disease in the RASopathies.

The RAS/mitogen-activated protein kinase (MAPK) pathway controls a plethora of developmental and post-developmental processes. It is now clear that mutations in the RAS-MAPK pathway cause developmental diseases collectively referred to as the RASopathies. The RASopathies include Noonan syndrome, Noonan syndrome with multiple lentigines, cardiofaciocutaneous syndrome, neurofibromatosis type 1, and Costello syndrome. RASopathy patients exhibit a wide spectrum of congenital heart defects (CHD), such as valvular abnormalities and hypertrophic cardiomyopathy (HCM). Since the cardiovascular defects are the most serious and recurrent cause of mortality in RASopathy patients, it is critical to understand the pathological signaling mechanisms that drive the disease. Therapies for the treatment of HCM and other RASopathy-associated comorbidities have yet to be fully realized. Recent developments have shown promise for the use of repurposed antineoplastic drugs that target the RAS-MAPK pathway for the treatment of RASopathy-associated HCM. However, given the impact of the RAS-MAPK pathway in post-developmental physiology, establishing safety and evaluating risk when treating children will be paramount. As such insight provided by preclinical and clinical information will be critical. This review will highlight the cardiovascular manifestations caused by the RASopathies and will discuss the emerging therapies for treatment.

DGAT1 mutation in two sisters with failure to thrive: a case report. / Mutación DGAT1 en dos hermanas con falla de medro: reporte de caso.

Congenital diarrhea and enteropathies (CODEs) are a group of monogenic disorders that have been described in recent years. Within the CODEs, the mutation in the diacylglycerol O-acyltransferase 1 (DGAT1) gene is a rare enzyme disorder associated with severe, early-onset chronic diarrhea. Our objective is to describe the case of 2 sisters who consulted for chronic diarrhea, growth retardation, vomiting, and hypoalbuminemia in early childhood. A compound heterozygous DGAT1 mutation was found in both patients. This mutation was previously described in the Asian population; however, these are the first 2 patients to show this mutation in the Latin American population. These 2 cases may expand our knowledge about congenital diarrhea in general and the clinical characteristics of patients with DGAT1 mutations in particular.

Las diarreas y enteropatías congénitas (CODE por su sigla en inglés) son un grupo de trastornos monogénicos que se han descrito en los últimos años. Dentro de las CODE, la mutación del gen de la diacilglicerol o-aciltransferasa 1 (DGAT1) es un trastorno enzimático poco común asociado con diarrea crónica grave de aparición temprana. El objetivo es presentar a dos hermanas que consultaron por diarrea crónica, retraso en el crecimiento, vómitos e hipoalbuminemia en la primera infancia. En ambas pacientes se encontró un compuesto heterocigota de la mutación del DGAT1. Esta mutación se describió previamente en la población asiática; sin embargo, estas son las dos primeras pacientes en tener esta mutación en la población latinoamericana. Estos dos casos pueden ampliar nuestro conocimiento sobre las diarreas congénitas en general y las características clínicas de los pacientes con mutaciones en DGAT1 en particular.

Clinical overview on RASopathies.

RASopathies comprise a group of clinically overlapping developmental disorders caused by genetic variations affecting components or modulators of the RAS-MAPK signaling cascade, which lead to dysregulation of signal flow through this pathway. Noonan syndrome and the less frequent, clinically related disorders, Costello syndrome, cardiofaciocutaneous syndrome, Noonan syndrome with multiple lentigines, and Noonan syndrome-like disorder with loose anagen hair are part of the RASopathy spectrum and share a recognizable pattern of multisystem involvement. This review describes the "Noonan syndrome-like" phenotype as a common phenotypic signature of generalized developmental RAS pathway dysregulation. Distinctive features of the different entities are revisited against the background of the understanding of underlying genetic alterations and genotype correlations, which has evolved rapidly during the past 20 years, thereby leading to suggestions regarding the nosology of RASopathies.

Whole exome sequencing based identification of a case of cardiofaciocutaneous syndrome type 3: the benefits of new sequencing technology in children with neurodevelopmental delay.

We report the case of a boy with a prolonged diagnostic workup for global developmental delay alongside feeding difficulties, failure to thrive, pulmonary stenosis and macrocephaly. Following a series of diagnostic tests over the first 25 months of life, whole-exome sequencing was performed which diagnosed cardiofaciocutaenous syndrome type 3.Global developmental delay is a common presentation to general paediatric and community paediatric clinics. This prompts the search for an aetiology to describe the child's constellation of symptoms which often consists of a chromosomal microarray, neuroimaging and investigations for an inborn error of metabolism. With developments in genetic testing such as the reducing cost of clinical exome sequencing or whole-exome sequencing, could these testing strategies offer a more comprehensive first line test?This case not only demonstrates the features of cardiofaciocutaneous syndrome type 3 but the added value of modern genetic technologies in the diagnosis of children with global developmental delay.

The heart in RASopathies.

The cardiovascular phenotype associated with RASopathies has expanded far beyond the original descriptions of pulmonary valve stenosis by Dr Jaqueline Noonan in 1968 and hypertrophic cardiomyopathy by Hirsch et al. in 1975. Because of the common underlying RAS/MAPK pathway dysregulation, RASopathy syndromes usually present with a typical spectrum of overlapping cardiovascular anomalies, although less common cardiac defects can occur. The identification of the causative genetic variants has enabled the recognition of specific correlations between genotype and cardiac phenotype. Characterization and understanding of genotype-phenotype associations is not only important for counseling a family of an infant with a new diagnosis of a RASopathy condition but is also critical for their clinical prognosis with respect to cardiac disease, neurodevelopment and other organ system involvement over the lifetime of the patient. This review will focus on the cardiac manifestations of the most common RASopathy syndromes, the relationship between cardiac defects and causal genetic variation, the contribution of cardiovascular abnormalities to morbidity and mortality and the most relevant follow-up issues for patients affected by RAS/MAPK pathway diseases, with respect to cardiac clinical outcomes and management, in children and in the adult population.

[Clinical analysis of a child with cardio-facio-cutaneous syndrome due to a de novo variant of MAP2K1 gene].

OBJECTIVE: To explore the genotype-phenotype correlation of a patient with cardio-facio-cutaneous syndrome (CFCS) due to variant of the MAP2K1 gene. METHODS: DNA was extracted from peripheral blood samples of the infant and his parents and subjected to whole exome sequencing. Candidate variant was verified by Sanger sequencing. RESULTS: The patient had typical CFCS facies and developmental delay, and was found to harbor a de novo heterozygous c.389A>G (p.Tyr130Cys) missense variant in exon 3 of the MAP2K1 gene. Based on the American college of Medical Genetics and Genomics guidelines, this variant was classified as likely pathogenic. CONCLUSION: This patient has differed from previously reported cases by having no cardiac anomaly or seizures but typical facial features and skin abnormalities accompanied by growth retardation, intellectual impairment, and urinary malformation. It has therefore enriched the phenotypic spectrum of CFCS due to variants of the MAP2K1 gene.

Cancer-causing MAP2K1 mutation in a mosaic patient with cardio-facio-cutaneous syndrome and immunodeficiency.

RASopathies are disorders caused by germline mutations in genes that encode components of the RAS/mitogen-activated protein kinase (MAPK) pathway. These syndromes share features of developmental delay, facial dysmorphisms, and defects in various organs, as well as cancer predisposition. Somatic mutations of the same pathway are one of the primary causes of cancer. It is thought that germline cancer-causing mutations would be embryonic lethal, as a more severe phenotype was shown in Drosophila and zebrafish embryos with cancer MAP2K1 mutations than in those with RASopathy mutations. Here we report the case of a patient with RASopathy caused by a cancer-associated MAP2K1 p.Phe53Leu mutation. The postzygotic mosaic nature of this mutation could explain the patient's survival.

EEF1A2 pathogenic variant presenting in an infant with failure to thrive and frequent apneas requiring respiratory support.

EEF1A2 is a gene whose protein product, eukaryotic translation elongation factor 1 alpha 2 (eEF1A2), plays an important role in neurodevelopment. Reports of individuals with pathogenic variants in EEF1A2 are rare, with less than 40 individuals reported world-wide, however a common feature is the association of the variant with developmental and epileptic encephalopathy. Thus far, there have been limited reports of other organ systems or body functions affected by variants in this gene. Here, we present a case of a child with EEF1A2-related disorder who presented at 3 months of age with hypotonia, microcephaly, failure to thrive, and respiratory insufficiency with central apneas requiring respiratory support. Our case highlights the notion that the respiratory system may be highly implicated in EEF1A2-related disorder, allowing for better phenotypic characterization of the disorder.

Severe neuroglycopenic symptoms due to nonketotic hypoglycemia in children with cardio-facio-cutaneous syndrome.

Cardio-facio-cutaneous syndrome (CFC) (OMIM 115150) is a congenital disease caused by constitutive activation of the Raf/MEK/ERK signaling cascade. Unlike aspects of morphological anomalies, metabolic functions related to the disease have garnered little attention. We present severe neuroglycopenic symptoms due to nonketotic hypoglycemia in two children with CFC (Case 1, a 4-year-old male with c.389A > G heterozygous variant in MAP2K1; Case 2, a 3-year-old male with c.770A > G heterozygous variant in BRAF). Case 1 exhibited a nonketotic hypoglycemic coma and clustered left-hemispheric convulsions despite receiving infusion therapy, leading to severe sequelae with choreoathetosis. Brain magnetic resonance imaging of Case 1 showed T2-elongation with restricted diffusion on the bilateral basal ganglia and thalamus, with the dominance of the right putamen. Case 2 presented a prolonged generalized seizure as an initial clinical symptom but fully recovered. The presence of growth hormone and cortisol deficiency was ruled out in both cases. Blood spots acylcarnitine profiles excluded the co-occurrence of mitochondrial HMG-CoA synthase deficiency and HMG-CoA lyase deficiency. These cases demonstrate the potential vulnerability to nonketotic hypoglycemia, especially during lipid shortages. As children with CFC frequently have difficulties feeding, we suggest great attention should be paid to the potential risk of severe nonketotic hypoglycemia.

Fibrous dysplasia in cardio-facio-cutaneous syndrome: A case report and review of literature.

Cardio-facio-cutaneous (CFC) syndrome (OMIM #:115150, 615278, 615279, 615280) is a rare genetic condition caused by variants in the RAS/mitogen-activated protein kinase (MAPK) signal transduction pathway. Up to 75% of cases are caused by mutations in the BRAF gene, whereas KRAS gene mutation has only been reported in <2% of cases. CFC syndrome is characterized by cardiac abnormalities, distinctive craniofacial dysmorphism, and various cutaneous abnormalities. Musculoskeletal and orthopedic manifestations are also prevalent in patients with CFC syndrome, among which the most common are skeletal deformities and joint laxities. Dysplastic bone disorders, on the other hand, have not been reported in CFC syndrome before. We report on a case of symmetrical polyostotic fibrous dysplasia (FD) in a patient with CFC syndrome with the KRAS(NM_004985.5):c.57G>C; p.Leu19Phe variant. The FDs were incidentally picked up, and patient was conservatively managed and remained asymptomatic on follow-up. The same variant was reported previously in a patient with Oculoectodermal Syndrome (OES), who developed polyostotic non-ossifying fibroma (NOF). This case explores FD as a possible new clinical feature of CFC syndrome, and when linked to the historical case of OES, explores whether the KRAS(NM_004985.5):c.57G>C; p.Leu19Phe mutation may potentially contribute to the development of dysplastic bone lesions in patients with this particular mutation.