Characteristic MR Imaging Findings of the Neonatal Brain in RASopathies

New Insights Into the Spectrum of RASopathies: Clinical and Genetic Data in a Cohort of 121 Spanish Patients

Noonan syndrome and related disorders are a group of well-known genetic conditions caused by dysregulation of the Ras/mitogen-activated protein kinase (RAS/MAPK) pathway. Because of the overlap of clinical and molecular features, they are now called RASopathies. In this study, we retrospectively analyzed the clinical data of 121 patients with a molecularly confirmed diagnosis of RASopathy, describing frequencies for clinical features in all organ systems as well as molecular data. The most common clinical diagnosis was Noonan Syndrome and the most frequently affected gene was PTPN11 followed by SOS1, RAF1, LZTR1, and RIT1. All patients had distinctive craniofacial features indicative of the RASopathy spectrum but we report some atypical features regarding craniofacial shape, such as craniosynostosis and microcephaly. We also describe uncommon clinical characteristics such as aortic dilation, multivalvular heart disease, abnormalities of the posterior fossa, and uterine congenital anomalies in female patients. Furthermore, the presence of multiple giant cell granulomas was observed specifically in patients with SOS1 variants. This comprehensive evaluation allows broadening the phenotypic spectrum of our population and their correlation with the genotype, which are essential to improve the recognition and the follow up of RASopathies as a multisystemic disease.

Social Communication in Ras Pathway Disorders: A Comprehensive Review from Genetics to Behavior in Neurofibromatosis Type 1 and Noonan Syndrome

Neurofibromatosis type 1 (NF1) and Noonan syndrome (NS) are neurogenetic syndromes caused by pathogenetic variants encoding components of the Ras-ERK-MAPK signaling pathway (Ras pathway). NF1 and NS are associated with differences in social communication and related neuropsychiatric risks. During the last decade, there has been growing interest in Ras-linked syndromes as models to understand social communication deficits and autism spectrum disorders. We systematically review the literature between 2010-2023 focusing on the social communication construct of the RDoC framework. We provide an integrative summary of the research on facial and non-facial social communication processes in NF1 and NS across molecular, cellular, neural circuitry, and behavioral domains. At the molecular and cellular levels, dysregulation in the Ras pathway is intricately tied to variations in social communication through changes in GABAergic, glutamatergic, and serotonergic transmission, as well as inhibitory/excitatory imbalance. Neural circuitry typically associated with learning, attention, and memory in NF1 and NS (e.g., cortico-striatal connectivity), is also implicated in social communication. We highlight less researched, potential mechanisms for social communication, such as white matter connectivity and the default mode network. Finally, key gaps in NF1 and NS literature are identified and a roadmap for future research is provided. By leveraging genetic syndromes research, we can understand the mechanisms associated with behaviors and psychiatric disorders.

Noonan syndrome: Neuroimaging findings and morphometric analysis of the cranium base and posterior fossa in children

BACKGROUND AND PURPOSE

There are a few studies regarding intracranial findings in neonates with Noonan syndrome (NS); however, there are no quantitative analyses in a pediatric population. The aim of this study was to find characteristic intracranial abnormalities and to quantitatively analyze the posterior fossa and cranium base in children with NS.

METHODS

A total of 30 patients (11 females and 19 males, mean age 13.1 ± 4.3 years) were retrospectively identified between July 2017 and June 2022. Twenty-one patients had MRI. Age at MRI examination, sex, genetic mutations, and clinical findings were noted. In patients with MRI, the presence of white matter lesions, basal ganglia lesions, corpus callosum abnormalities, sellar/parasellar lesions, and tonsillar ectopia was noted. For morphometric analysis, cerebellar diameter, vermis and clivus heights, cranial base, tentorial and infratentorial angles, and McRae's and Twining's lines were each measured twice by two radiologists individually.

RESULTS

The most common lesions were focal white matter lesions, followed by abnormalities of the splenium of the corpus callosum. The cerebellar diameter, vermis and clivus heights, Twining's line, and infratentorial angle were significantly smaller; cranial base angle and tentorial angle were significantly larger in NS (p < .05). Interrater and intrarater agreements were the highest for cerebellar diameter and the lowest for tentorial angle measurements.

CONCLUSION

Children with NS had characteristic callosal and tentorial findings and neuroimaging findings similar to other RASopathies. This study also shows that a small posterior fossa and flattening of the cranial base are present in children with NS, which may aid in diagnosis.

Central nervous system involvement in individuals with RASopathies

Central nervous system (CNS) anomalies are common in individuals with RASopathies. While certain findings, including relative or absolute macrocephaly, are typical for most RASopathies, other findings are more common in certain conditions, with rare low-grade gliomas in Noonan syndrome (NS); Chiari 1 malformation and tethered cord in Costello syndrome (CS); and variable structural anomalies including heterotopia and hydrocephalus in cardio-facio-cutaneous syndrome (CFC). We performed a literature review and present aggregate data on the common and uncommon CNS manifestations in individuals with RASopathies. A gene-based approach to defining risk for specific abnormalities may be considered. However, limited information on the CNS findings of rare RASopathies, such as autosomal recessive LZTR1-related NS or PPP1CB-related NS with loose anagen hair (NSLH), is currently available. Thus, consideration of the RASopathies as a group of distinct syndromic conditions with shared underlying causes and overlapping clinical presentations remains relevant, and individuals with a RASopathy are at risk for many findings seen in these conditions.

Detailed prenatal and postnatal MRI findings and clinical analysis of RAF1 in Noonan syndrome

Noonan syndrome is a genetically heterogeneous developmental disorder, which usually includes findings such as short stature, facial dysmorphia, cardiac abnormalities and a varying degree of intellectual disability. We present a unique case of a rare variant of Noonan syndrome in a very preterm female infant born at 28 + 4 gestational weeks, with abnormal radiological findings visible at fetal magnetic resonance imaging (MRI) and evolution of the brain lesions during infancy.

Brain structural changes in patients with cardio-facio-cutaneous syndrome: effects of BRAF gene mutation and epilepsy on brain development. A case-control study by quantitative magnetic resonance imaging

PURPOSE

To evaluate the brain volumetric changes caused by BRAF gene mutation in non-epileptic CFC patients and the influence of the age of epilepsy onset on brain development in 2 cohorts of epileptic CFC patients.

METHODS

We enrolled CFC patients carrying BRAF gene mutations without epilepsy (4 patients) and with epilepsy (16 patients). CFC epileptic patients were divided into two cohorts based on the age of seizure onset: early-age onset (7 children) and late-age onset (9 adolescents). All three cohorts of patients underwent 3D FSPGR T1-weighted imaging to assess supratentorial and infratentorial brain volumes. Moreover, for each compartment, gray matter (GM), white matter (WM), and cerebrospinal fluid (CSF) volumes were measured. All measurements were compared with those of age-matched controls without neuroimaging abnormalities.

RESULTS

All CFC patients showed supratentorial and infratentorial WM reduction and supratentorial ventricular enlargement (p < 0.01). However, patients with early age of epilepsy onset, compared with the other two cohorts of CFC patients, showed both GM and a more pronounced WM volume reduction (p < 0.01).

CONCLUSION

In non-epileptic CFC children, we demonstrated WM volumetric reduction suggesting a direct effect of BRAF gene mutation on brain development. Nevertheless, in CFC epileptic patients, the age of epilepsy onset may contribute to brain atrophy. Brain atrophy in CFC patients, in part due to the natural history of the disease, may be worsened by epilepsy when it begins in the early ages because of interference with brain growth at that critical age of development.

External hydrocephalus as a prenatal feature of noonan syndrome

Brain malformations have been reported in RASopathies, including postnatal external hydrocephalus, a nonobstructive form of cerebrospinal fluid accumulation around the brain. It was described in a few patients with mutations of other genes than PTPN11, such as SOS1 and SHOC2 and never in prenatal diagnosis. The aim of this case report is to describe the prenatal presentation of a fetus with Noonan syndrome (NS) and external hydrocephalus. We report on a Noonan syndrome fetus with a de novo pathogenic PTPN11 c.923A>G p.Asn308Ser mutation, showing external hydrocephalus, an extremely rare fetal finding, corpus callosum, and cerebellar vermis under the 10th centile, plus a typical NS cardiopathy. This is the first case of Noonan syndrome prenatal diagnosis in a fetus presenting with external hydrocephalus. Following pathophysiological considerations, we suggest to consider NS in the differential diagnosis of external hydrocephalus, investigating other evocative findings and considering molecular screening for mutations in NS-related genes.

Maternal SLE and brachytelephalangic chondrodysplasia punctata in a patient with unrelated de novo RAF1 and SIX2 variants

Our improved tools to identify the aetiologies in patients with multiple abnormalities resulted in the finding that some patients have more than a single genetic condition and that some of the diagnoses made in the past are acquired rather than inherited. However, limited knowledge has been accumulated regarding the phenotypic outcome of the interaction between different genetic conditions identified in the same patients. We report a newborn girl with brachytelephalangic chondrodysplasia punctata (BCDP) as well as frontonasal dysplasia, ptosis, bilateral hearing loss, vertebral anomalies, and pulmonary hypoplasia who was found, by whole exome sequencing, to have a de novo pathogenic variant in RAF1 (c.770C>T, [p.Ser257Leu]) and a likely pathogenic variant in SIX2 (c.760G>A [p.A254T]), as well as maternal systemic lupus erythematosus (SLE). This case shows that BCDP is most probably not a diagnostic entity and can be associated with various conditions associated with CDP including maternal SLE.

Sinus pericranii, skull defects, and structural brain anomalies in TRAF7-related disorder

BACKGROUND

Several somatic mutations in TRAF7 have been reported in cancers, whereas a few germline heterozygous mutations have been recently linked to a neurodevelopmental disorder, characterized by craniofacial dysmorphisms, congenital heart defects, and digital anomalies.

CASES

We report two subjects harboring de novo heterozygous missense variants in TRAF7, namely the recurrent 1964G>A(p.Arg655Gln) and the novel missense c.1204C>G(p.Leu402Val) variants. In addition to the typical hallmarks of the TRAF7-related disorder, both subjects presented with a recognizable "pear-shaped" skull due to multiple craniosynostosis, sinus pericranii, skull base/cranio-cervical junction anomalies, dysgyria, and inferior cerebellar vermis hypoplasia.

CONCLUSIONS

Hence, we expand the genotypic and phenotypic spectrum of this neurodevelopmental disorder, discussing possible implications for clinical management of subjects with germline TRAF7 mutations.

The sixth international RASopathies symposium: Precision medicine-From promise to practice

The RASopathies are a group of genetic disorders that result from germline pathogenic variants affecting RAS-mitogen activated protein kinase (MAPK) pathway genes. RASopathies share RAS/MAPK pathway dysregulation and share phenotypic manifestations affecting numerous organ systems, causing lifelong and at times life-limiting medical complications. RASopathies may benefit from precision medicine approaches. For this reason, the Sixth International RASopathies Symposium focused on exploring precision medicine. This meeting brought together basic science researchers, clinicians, clinician scientists, patient advocates, and representatives from pharmaceutical companies and the National Institutes of Health. Novel RASopathy genes, variants, and animal models were discussed in the context of medication trials and drug development. Attempts to define and measure meaningful endpoints for treatment trials were discussed, as was drug availability to patients after trial completion.

ADA2 deficiency in a patient with Noonan syndrome-like disorder with loose anagen hair: The co-occurrence of two rare syndromes

Noonan syndrome-like disorder with loose anagen hair (NS/LAH) is one of the RASopathies, a group of clinically related developmental disorders caused by germline mutations in genes that encode components acting in the RAS/MAPK pathway. Among RASopathies, NS/LAH (OMIM 607721) is an extremely rare, multiple anomaly syndrome characterized by dysmorphic facial features similar to those observed in Noonan syndrome along with some distinctive ectodermal findings including easily pluckable, sparse, thin, and slow-growing hair. ADA2 deficiency (DADA2, OMIM 615688) is a monogenic autoinflammatory disorder caused by homozygous or compound heterozygous mutations in ADA2, with clinical features including recurrent fever, livedo racemosa, hepatosplenomegaly, and strokes as well as immune dysregulation. This is the first report of NS/LAH and ADA2 deficiency in the same individual. We report on a patient presenting with facial features, recurrent infections and ectodermal findings in whom both the clinical and molecular diagnoses of NS/LAH and ADA2 deficiency were established, respectively.