A Narrative Review of the Ocular Manifestations in Noonan Syndrome

Congenital ectropion in Noonan syndrome

Ten-year-old female patient, with facial dysmorphia, scoliosis, short stature, muscular hypotonia, patent foramen ovale and maturational delay, presented for correction of bilateral congenital ectropion. Ophthalmological examination revealed bilateral lower eyelid ectropion, euryblepharon and lagophthalmos, with a positive Bell's phenomenon. She was treated with full-thickness autologous skin grafts on the lower eyelids with bilateral lateral canthoplasty, resolving the ectropion and improving eyelid occlusion. Subsequently, a genetic study was performed that revealed a mutation in the PTPN11 gene and allowed, together with the clinical picture, to make the diagnosis of Noonan syndrome. Noonan syndrome is a multisystem genetic disorder with a wide variety of phenotypes, which usually presents with ocular and periocular disorders. Eyelid ectropion, a distinctive feature of this patient, is a rare ophthalmological manifestation of this syndrome that can be corrected with full-thickness skin graft and lateral canthoplasty.

Phenotypic and genotypic spectrum of noonan syndrome: A retrospective analysis of 46 consecutive pediatric patients presented at a regional cardiac center in China

Background

Noonan syndrome (NS) is relatively common but poorly recognized. We aimed to describe the phenotypic and genotypic spectrum of NS in a Chinese cohort.

Method

The study retrospectively investigated consecutive pediatric patients who presented at the Guangdong cardiovascular institute between 2018 and 2020 with confirmed known NS-relevant mutations determined by exome sequencing. Dates of genetic testing, Age, sex, institution of genetic testing, mutated gene (related to NS) and its classification, heterozygosity, and parental origin were identified from the sequencing reports. Facial features, cardiac defect and other clinical characteristics were also assessed. Comparisons of categorical variables between groups were examined by Chi-square test or Fisher's exact test when appropriate. Intraclass correlation coefficient (ICC) was performed to evaluate the reliability of evaluation of facial features between different evaluators.

Results

The most prevalent mutated genes were PTPN11 (37.0%) and RAF1 (19.6%), and most mutations were pathogenic (67.4%) and de novo (87.0%). Most patients were with NS-relevant facial features (97.4%) and cardiac defects (92.7%), where ventricular hypertrophy, pulmonary valve stenosis, and atrial septal defect were the most prevalent. Patients with mutated RAF1 appeared to be diagnosed at an older age than those with mutated PTPN11, and with higher prevalence of mitral regurgitation, hypertrophic cardiomyopathy, and ventricular hypertrophy, but lower prevalence of pulmonary valve stenosis and pulmonary artery stenosis. Patients presented at an age ≥2 years appeared to be with fewer NS-relevant facial features and cardiac defects than those aged <2 years.

Conclusions

These findings indicated featured distributions of phenotypic and genotypic spectrum in Chinese pediatric patients, which might be helpful for early NS diagnosis.

Systematic ophthalmologic evaluation in cardio-facio-cutaneous syndrome: A genotype-endophenotype correlation

Cardio-facio-cutaneous syndrome (CFCS) is a rare genetic disorder belonging to the RASopathies, a group of developmental syndromes caused by upregulated RAS/MAPK signaling. Pathogenic variants affecting four genes, KRAS, BRAF, MAP2K1 and MAP2K2, encoding core signal transducers of the pathway, underlie the condition. Major clinical features include a distinctive facies, ectodermal and cardiac anomalies, reduced postnatal growth, intellectual disability, and musculoskeletal abnormalities. Similar to other RASopathies, reports of visual impairment, high refractive error, optic nerve pallor, and other ocular abnormalities have been anecdotally reported in the literature. The aim of our study is to report the prevalence of ophthalmologic abnormalities in a large monocentric cohort of individuals affected by CFCS and explore the occurrence of genotype-endophenotype correlations in this series of patients. We observed that BRAF mutations are associated to a higher prevalence of anisometropia >3D (11.8% vs. 0%) and high astigmatism (29.4% vs. 0%; both p < 0.001) while patients with mutations in other genes had a significantly higher prevalence of myopia >6 D (60% vs. 5.9%; p = 0.012). Pale optic disc was associated with higher prevalence of inferior oblique muscle (IO) overaction (33.3% vs. 0%) and lower prevalence of ptosis (0% vs. 11.8%; both p < 0.001). Combined exotropia, IO overaction and nystagmus were frequent in patients with pale optic nerve. Our findings might suggest the need for earlier ophthalmologic referral for CFCS patients due to high risk of amblyopia, especially those expressing BRAF mutations.

Anterior Uveitis and Coats Disease in a 16-Year-Old Girl with Noonan Syndrome-A Case Report

Background: Noonan syndrome (NS) represents a fairly common genetic disorder with a highly variable phenotype. Its features include inherited heart defects, characteristic facial features, short stature, and mild retardation of motor skills. Case presentation: A 16-year-old Caucasian girl with NS reported visual deterioration, photophobia, and pain in the right eye (RE). The initial best-corrected visual acuity (BCVA) was 0.3 in the RE. An examination demonstrated conjunctival and ciliary body hyperemia, keratic precipitates, and flare in the anterior chamber. In addition, post-hemorrhagic floaters, tortuous vessels, and an epiretinal membrane in the RE were present. Diagnosis of unilateral anterior uveitis was made, and this resolved after the use of topical steroids and cycloplegic drops. Due to the presence of retinal telangiectasias and extraocular exudates (consistent with Coats' disease (CD) stage 2A) in the RE, laser therapy was performed. The patient remains under constant follow-up, and after one year, the BCVA in the RE was 0.7. Conclusions: Here, we report the clinical characteristics, genetic findings, and retinal imaging results of a patient with NS. To our knowledge, this is, to date, the first report of an association of NS with a PTPN11 mutation with anterior uveitis and CD.

Neurodevelopmental disorders, immunity, and cancer are connected

Immunity could be viewed as the common factor in neurodevelopmental disorders and cancer. The immune and nervous systems coevolve as the embryo develops. Immunity can release cytokines that activate MAPK signaling in neural cells. In specific embryonic brain cell types, dysregulated signaling that results from germline or embryonic mutations can promote changes in chromatin organization and gene accessibility, and thus expression levels of essential genes in neurodevelopment. In cancer, dysregulated signaling can emerge from sporadic somatic mutations during human life. Neurodevelopmental disorders and cancer share similarities. In neurodevelopmental disorders, immunity, and cancer, there appears an almost invariable involvement of small GTPases (e.g., Ras, RhoA, and Rac) and their pathways. TLRs, IL-1, GIT1, and FGFR signaling pathways, all can be dysregulated in neurodevelopmental disorders and cancer. Although there are signaling similarities, decisive differentiating factors are timing windows, and cell type specific perturbation levels, pointing to chromatin reorganization. Finally, we discuss drug discovery.

How can same-gene mutations promote both cancer and developmental disorders?

The question of how same-gene mutations can drive both cancer and neurodevelopmental disorders has been puzzling. It has also been puzzling why those with neurodevelopmental disorders have a high risk of cancer. Ras, MEK, PI3K, PTEN, and SHP2 are among the oncogenic proteins that can harbor mutations that encode diseases other than cancer. Understanding why some of their mutations can promote cancer, whereas others promote neurodevelopmental diseases, and why even the same mutations may promote both phenotypes, has important clinical ramifications. Here, we review the literature and address these tantalizing questions. We propose that cell type–specific expression of the mutant protein, and of other proteins in the respective pathway, timing of activation (during embryonic development or sporadic emergence), and the absolute number of molecules that the mutations activate, alone or in combination, are pivotal in determining the pathological phenotypes—cancer and (or) developmental disorders.