Case report: Identification of a novel variant p.Gly215Arg in the CHN1 gene causing Moebius syndrome

Background: Moebius Syndrome (MBS) is a rare congenital neurological disorder characterized by paralysis of facial nerves, impairment of ocular abduction and other variable abnormalities. MBS has been attributed to both environmental and genetic factors as potential causes. Until now only two genes, PLXND1 and REV3L have been identified to cause MBS. Results: We present a 9-year-old male clinically diagnosed with MBS, presenting facial palsy, altered ocular mobility, microglossia, dental anomalies and congenital torticollis. Radiologically, he lacks both abducens nerves and shows altered symmetry of both facial and vestibulocochlear nerves. Whole-exome sequence identified a de novo missense variant c.643G>A; p.Gly215Arg in CHN1, encoding the α2-chimaerin protein. The p.Gly215Arg variant is located in the C1 domain of CHN1 where other pathogenic gain of function variants have been reported. Bioinformatic analysis and molecular structural modelling predict a deleterious effect of the missense variant on the protein function. Conclusion: Our findings support that pathogenic variants in the CHN1 gene may be responsible for different cranial congenital dysinnervation syndromes, including Moebius and Duane retraction syndromes. We propose to include CHN1 in the genetic diagnoses of MBS.

Moebius Syndrome: A Case Report on an Uncommon Congenital Syndrome

Moebius syndrome (MS) is rare. It is defined by congenital bilateral paralysis of the sixth and seventh cranial nerves, resulting in an absence of mimicry and strabismus responsible for major relational disorders. Other cranial nerves can also be affected (third, fourth, fifth, ninth, tenth, and twelfth cranial pairs). In the majority of cases, MS is sporadic, causing problems with sucking, swallowing, breathing, and phonation. Associated malformations have also been reported. The disease is not progressive, and management is mainly symptomatic. We report a three-year-old girl who presented with facial asymmetry and in whom the MS was confirmed through magnetic resonance imaging (MRI). A multidisciplinary approach was conducted on our patient and is currently being followed up in the neuropediatrics department, and an ophthalmological examination is scheduled. Additionally, she had medical consultations with a plastic surgeon for smile rehabilitation. On the other hand, psychological support was maintained.

Moebius Syndrome: What We Know So Far

Moebius syndrome (MBS) is a rare congenital cranial nerve disorder characterized by unilateral, bilateral symmetrical, or asymmetrical facial (VII) and abducens (VI) nerve palsies. Genetics and rhombencephalon vascular disturbances from intrauterine environmental exposures have been attributed to its development. It can present with various orofacial abnormalities. Although the diagnosis is purely clinical, certain characteristic features are present in the brain's images. With no cure, it is essential to devise management on a personalized basis. We discuss etiology, presentation, diagnostic approaches, and effective management in the existing literature. This comprehensive review examines the clinic-pathological aspects of Moebius syndrome. The authors employed the PUBMED base index to identify pertinent literature and reference it according to research keywords. Findings suggest the most popular etiology is the theory of intrauterine vascular disruption to the brainstem during embryogenesis, followed by the genetic hypothesis. Intrauterine environmental exposures have been implicated as potential risk factors. Facial and abducens nerve palsies are the most common presenting features. However, clinical manifestations of lower cranial nerves (IX, X, XI, XII) may be present with orthopedic anomalies and intellectual deficiencies. The diagnosis is clinical with minimal defined diagnostic criteria. Characteristic radiological manifestations involving the brainstem and cerebellum can be observed in imaging studies. With no definitive treatment options, a multidisciplinary approach is employed to provide supportive care. Despite radiological manifestations, Moebius syndrome is diagnosed clinically. Although incurable, a multidisciplinary approach, with personalized rehabilitative measures, can manage physical and psychological deficits; however, standard guidelines need to be established.

Simultaneous Bilateral Proximal Femur Implant Failure: A Case Report

A seven-year-old boy with Moebius syndrome and bilateral hip dysplasia underwent left-sided adductor lengthening, bilateral proximal femur varus derotational osteotomies, and internal fixation with proximal femur blade plates, and left-sided Dega pelvic osteotomy. Postoperatively, he was immobilized in a Petrie cast. A month later, the child presented with bilateral proximal femur blade plate implant failure. Simultaneous bilateral proximal femur implant failure in a child, to our knowledge, has not yet been reported. Implant failure in the absence of significant trauma is rare. We describe various contributory factors that may lead to implant failure which must be carefully considered while managing a non-ambulatory child.

Moebius Syndrome with Hypoglossal Palsy, Syndactyly, Brachydactyly, and Anisometropic Amblyopia

Moebius syndrome is a rare cause of congenital facial and abducens palsy. It is sometimes associated with musculoskeletal abnormalities and other cranial nerve palsies. Genetics and ischemic insults to the fetus are considered to be the cause of this syndrome. We report here a 12-year-old female patient who was presented to us with poor cosmesis of her face, with associated decreased vision and lagophthalmos in her left eye. She didn't have any signs of exposure keratopathy in the affected eye. Her best-corrected vision was 20/20 and 20/60 in right and left eyes respectively. The cause of decreased vision in her left eye was found to be anisometropic amblyopia, due to asymmetric hyperopic astigmatism in her eyes. She did not report diplopia in any gaze position. Examination of her cranial nerve revealed left facial, abducens, and hypoglossal nerve palsy, leading us to the diagnosis of Moebius syndrome. Apart from that, she had syndactyly in one of her hands, and brachydactyly in both. Since the eyes were straight in their primary position, no surgical intervention was carried out for her lagophthalmos, which was measured to be only 2 mm. This was to prevent any post-operative iatrogenic ptosis. The condition requires a multidisciplinary approach involving the opinions of a neuro-ophthalmologist, strabismologist, and oculoplastics for the management of the complications associated with the disease.