Otopalatodigital spectrum disorders: refinement of the phenotypic and mutational spectrum

Periventricular nodular heterotopias is associated with mutation at the FLNA locus-a case history and a literature review

BACKGROUND

Periventricular nodular heterotopia (PNH), associated with FLNA mutations, is a rare clinical condition potentially associated with multiple systemic conditions, including cardiac, pulmonary, skeletal, and cutaneous diseases. However, due to a paucity of information in the literature, accurate prognostic advice cannot be provided to patients with the disease.

CASE PRESENTATION

We report a 2-year-old female whose PNH was associated with a nonsense mutation in the q28 region of the X chromosome, in exon 31 of FLNA (c.5159dupA). The patient is currently seizure-free and has no congenital heart disease, lung disease or skeletal or joint issues, and her development is normal.

CONCLUSIONS

FLNA-associated PNH is a genetically-heterogeneous disease, and the FLNA mutation, c.5159dupA (p.Tyr1720*) is a newly identified pathogenic variant. FLNA characterization will help the clinical diagnosis and treatment of PNH and provide individualized genetic counseling for patients.

Homozygous loss-of-function variants in FILIP1 cause autosomal recessive arthrogryposis multiplex congenita with microcephaly

Arthrogryposis multiplex congenita forms a broad group of clinically and etiologically heterogeneous disorders characterized by congenital joint contractures that involve at least two different parts of the body. Neurological and muscular disorders are commonly underlying arthrogryposis. Here, we report five affected individuals from three independent families sharing an overlapping phenotype with congenital contractures affecting shoulder, elbow, hand, hip, knee and foot as well as scoliosis, reduced palmar and plantar skin folds, microcephaly and facial dysmorphism. Using exome sequencing, we identified homozygous truncating variants in FILIP1 in all patients. FILIP1 is a regulator of filamin homeostasis required for the initiation of cortical cell migration in the developing neocortex and essential for the differentiation process of cross-striated muscle cells during myogenesis. In summary, our data indicate that bi-allelic truncating variants in FILIP1 are causative of a novel autosomal recessive disorder and expand the spectrum of genetic factors causative of arthrogryposis multiplex congenita.

Whole-Exome Sequencing Identified Rare Genetic Variants Associated with Undervirilized Genitalia in Taiwanese Pediatric Patients

Disorders/differences of sex development (DSDs) are a group of rare and phenotypically variable diseases. The underlying genetic causes of most cases of 46XY DSDs remains unknown. Despite the advent of genetic testing, current investigations of the causes of DSDs allow genetic-mechanism identification in about 20-35% of cases. This study aimed primarily to establish a rapid and high-throughput genetic test for undervirilized males with and without additional dysmorphic features. Routine chromosomal and endocrinological investigations were performed as part of DSD evaluation. We applied whole-exome sequencing (WES) complemented with multiplex ligation-dependent probe amplification to seek explainable genetic causes. Integrated computing programs were used to call and predict the functions of genetic variants. We recruited 20 patients and identified the genetic etiologies for 14 (70%) patients. A total of seven of the patients who presented isolated DSD phenotypes were found to have causative variants in the AR, MAP3K1, and FLNA genes. Moreover, the other seven patients presented additional phenotypes beyond undervirilized genitalia. Among them, two patients were compatible with CHARGE syndrome, one with Robinow syndrome, and another three with hypogonadotropic hypogonadism. One patient, who carried a heterozygous FLNA mutation, also harbored a heterozygous PTPN11 mutation and thus presented some phenotypes of Noonan syndrome. We identified several genetic variants (12 nonsense mutations and one microdeletion) that account for syndromic and nonsyndromic DSDs in the Taiwanese population. The identification of these causative genes extended our current understanding of sex development and related congenital disorders.

UVB mutagenesis differs in Nras- and Braf-mutant mouse models of melanoma

BRAF-mutant melanomas are more likely than NRAS-mutant melanomas to arise in anatomical locations protected from chronic sun damage. We hypothesized that this discrepancy in tumor location is a consequence of the differential sensitivity of BRAF and NRAS-mutant melanocytes to ultraviolet light (UV)-mediated carcinogenesis. We tested this hypothesis by comparing the mutagenic consequences of a single neonatal, ultraviolet-AI (UVA; 340-400 nm) or ultraviolet-B (UVB; 280-390 nm) exposure in mouse models heterozygous for mutant Braf or homozygous for mutant Nras Tumor onset was accelerated by UVB, but not UVA, and the resulting melanomas contained recurrent mutations affecting the RING domain of MAP3K1 and Actin-binding domain of Filamin A. Melanomas from UVB-irradiated, Braf-mutant mice averaged twice as many single-nucleotide variants and five times as many dipyrimidine variants than tumors from similarly irradiated Nras-mutant mice. A mutational signature discovered in UVB-accelerated tumors mirrored COSMIC signatures associated with human skin cancer and was more prominent in Braf- than Nras-mutant murine melanomas. These data show that a single UVB exposure yields a greater burden of mutations in murine tumors driven by oncogenic Braf.

Ciliary Signalling and Mechanotransduction in the Pathophysiology of Craniosynostosis

Craniosynostosis (CS) is the second most prevalent inborn craniofacial malformation; it results from the premature fusion of cranial sutures and leads to dimorphisms of variable severity. CS is clinically heterogeneous, as it can be either a sporadic isolated defect, more frequently, or part of a syndromic phenotype with mendelian inheritance. The genetic basis of CS is also extremely heterogeneous, with nearly a hundred genes associated so far, mostly mutated in syndromic forms. Several genes can be categorised within partially overlapping pathways, including those causing defects of the primary cilium. The primary cilium is a cellular antenna serving as a signalling hub implicated in mechanotransduction, housing key molecular signals expressed on the ciliary membrane and in the cilioplasm. This mechanical property mediated by the primary cilium may also represent a cue to understand the pathophysiology of non-syndromic CS. In this review, we aimed to highlight the implication of the primary cilium components and active signalling in CS pathophysiology, dissecting their biological functions in craniofacial development and in suture biomechanics. Through an in-depth revision of the literature and computational annotation of disease-associated genes we categorised 18 ciliary genes involved in CS aetiology. Interestingly, a prevalent implication of midline sutures is observed in CS ciliopathies, possibly explained by the specific neural crest origin of the frontal bone.

Frontometaphyseal dysplasia 1 in a patient from Sri Lanka

A Sri Lankan male child with supraorbital hyperostosis, broad nasal bridge, small mandible, severe kyphoscoliosis, distal joint contractures of the hands and long second and third toes is described. A hemizygous pathogenic variant in exon 22 of the filamin A (FLNA) gene [NM_001110556.1: c.3557C>T; which leads to a nonsynonymous substitution of serine by leucine at codon 1186 in the FLNA protein; NP_001104026.1: p.Ser1186Leu] was identified. The clinical features observed in this patient were consistent with the cardinal manifestations seen in frontometaphyseal dysplasia 1 (FMD1). However, characteristic extra skeletal manifestations such as cardiac defects, uropathy, and hearing impairment which have previously been reported in association with this condition were absent in this patient.

Prune belly syndrome in surviving males can be caused by Hemizygous missense mutations in the X-linked Filamin A gene

Background

Prune belly syndrome (PBS) is a rare, multi-system congenital myopathy primarily affecting males that is poorly described genetically. Phenotypically, its morbidity spans from mild to lethal, however, all isolated PBS cases manifest three cardinal pathological features: 1) wrinkled flaccid ventral abdominal wall with skeletal muscle deficiency, 2) urinary tract dilation with poorly contractile smooth muscle, and 3) intra-abdominal undescended testes. Despite evidence for a genetic basis, previously reported PBS autosomal candidate genes only account for one consanguineous family and single cases.

Methods

We performed whole exome sequencing (WES) of two maternal adult half-brothers with syndromic PBS (PBS + Otopalatodigital spectrum disorder [OPDSD]) and two unrelated sporadic individuals with isolated PBS and further functionally validated the identified mutations.

Results

We identified three unreported hemizygous missense point mutations in the X-chromosome gene Filamin A (FLNA) (c.4952 C > T (p.A1448V), c.6727C > T (p.C2160R), c.5966 G > A (p.G2236E)) in two related cases and two unrelated sporadic individuals. Two of the three PBS mutations map to the highly regulatory, stretch-sensing Ig19–21 region of FLNA and enhance binding to intracellular tails of the transmembrane receptor β-integrin 1 (ITGβ1).

Conclusions

FLNA is a regulatory actin-crosslinking protein that functions in smooth muscle cells as a mechanosensing molecular scaffold, transmitting force signals from the actin-myosin motor units and cytoskeleton via binding partners to the extracellular matrix. This is the first evidence for an X-linked cause of PBS in multiple unrelated individuals and expands the phenotypic spectrum associated with FLNA in males surviving even into adulthood.

Anterior Segment Dysgenesis With Accessory Iris Membranes in an Infant With Otopalatodigital Spectrum Disorder and Mutation in the FLNA Gene

A 4-month-old male infant with frontometaphyseal dysplasia and de novo FLNA gene mutation died of complications of disease. Post-mortem examination revealed accessory iris membranes. This is the first report in the literature of accessory iris membranes in a confirmed case of FLNA mutation and phenotypic anomalies consistent with frontometaphyseal dysplasia. [J Pediatr Ophthalmol Strabismus. 2020;57:e8-e11.].

A recurrent mutation causing Melnick-Needles syndrome in females confers a severe, lethal phenotype in males

Melnick-Needles syndrome (MNS; MIM 309350) is an X-linked skeletal dysplasia caused by mutations in FLNA. Females with the condition present with characteristic facial features, short stature, skeletal anomalies, including poorly modeled and sclerotic bones, and structural abnormalities such as cardiac and urological defects. Previously males were thought to present with either a mild phenotype compatible with life or a severe lethal presentation depending on the maternal phenotype. The discovery of a limited number of mutations in FLNA as the cause of the condition has clarified the molecular basis of the disorder, but only a very small number of severely affected males have been reported with MNS. Furthermore, no mildly affected males have been described with a molecular confirmation of the condition. In this report, we describe the clinical and molecular findings of a mildly affected mother with MNS and her severely affected son. They shared a well-documented disease-causing variant in FLNA, p.(Ala1188Thr), one of two highly recurrent mutations leading to the disorder. This is only the fourth report of a male with perinatal lethal MNS and a molecular confirmation; it is the first description of this specific mutation in a male.

Craniofacial and Dental Manifestations of Melnick-Needles Syndrome: Literature Review and Orthodontic Management

The aim of this article was to present a characteristic clinical image of Melnick–Needles syndrome using an example of an 11.5-year-old female patient treated at the Facial Congenital Disorders Outpatient Clinic as well as to present the actual literature review of the surgical treatment. The patient was diagnosed with several characteristics typical for Melnick–Needles syndrome: single-sided hearing loss, malocclusion, and facial dysmorphism, among others. Due to malocclusion and facial dysmorphism, the patient with Melnick–Needles syndrome requires orthodontic treatment with surgical intervention. Mandibular distraction with fixed appliance treatment is a recommended treatment protocol.

FLNA mutations in surviving males presenting with connective tissue findings: two new case reports and review of the literature

Background

Mutations in the X-linked gene filamin A (FLNA), encoding the actin-binding protein FLNA, cause a wide spectrum of connective tissue, skeletal, cardiovascular and/or gastrointestinal manifestations. Males are typically more severely affected than females with common pre- or perinatal death.

Case presentation

We provide a genotype- and phenotype-oriented literature overview of FLNA hemizygous mutations and report on two live-born male FLNA mutation carriers. Firstly, we identified a de novo, missense mutation (c.238C > G, p.(Leu80Val)) in a five-year old Indian boy who presented with periventricular nodular heterotopia, increased skin laxity, joint hypermobility, mitral valve prolapse with regurgitation and marked facial features (e.g. a flat face, orbital fullness, upslanting palpebral fissures and low-set ears). Secondly, we identified two cis-located FLNA mutations (c.7921C > G, p.(Pro2641Ala); c.7923delC, p.(Tyr2642Thrfs*63)) in a Bosnian patient with Ehlers-Danlos syndrome-like features such as skin translucency and joint hypermobility. This patient also presented with brain anomalies, pectus excavatum, mitral valve prolapse, pulmonary hypertension and dilatation of the pulmonary arteries. He died from heart failure in his second year of life.

Conclusions

These two new cases expand the list of live-born FLNA mutation-positive males with connective tissue disease from eight to ten, contributing to a better knowledge of the genetic and phenotypic spectrum of FLNA-related disease.

Electronic supplementary material

The online version of this article (10.1186/s12881-018-0655-0) contains supplementary material, which is available to authorized users.

Whole genome sequencing and 6-year follow-up of a mother and daughter with frontometaphyseal dysplasia associated with keratitis, xerosis, poikiloderma, and acro-osteolysis: A case report

RATIONALE

Frontometaphyseal dysplasia (FMD) is a dominant X-linked rare disease caused by mutations of FLNA. The distinctive features of FMD include skeletal dysplasia, facial dysmorphism, extremities anomalies, deafness, cleft palate and eye anterior segment anomalies, yet none of the complications, such as acro-osteolysis, keratitis, xerosis or poikiloderma, have been reported in FMD.

PATIENT CONCERNS

A 29-year-old mother and her 7-year-old daughter, both presented with congenital glaucoma, craniofacial dysmorphism, xerosis and poikiloderma, were admitted to our hospital in 2011. Additionally, the mother also suffered from acro-osteolysis, keratitis, camptodactyly of hands and metastatic cutaneous squamous cell carcinoma (SCC) which turned out to be fatal 5 years later. In 2017, keratitis and acro-osteolysis were noticed in the daughter as well. Radiography showed bowed long bones with thickening cortex, and distal phalangeal osteolysis.

DIAGNOSES

Whole genome sequencing (WGS) was conducted in 2016, resulting in 71491 single-nucleotide polymorphisms and 7616 indels shared by patients while the father was taken as control. A FLNA variant was classified likely pathogenic, supporting the diagnoses of FMD. In addition, though our patients' symptoms were highly consistent with xeroderma pigmentosum variant, a mild subtype of xeroderma pigmentosum (XP) with merely accumulated UV-induced lesions like xerosis and poikiloderma limited to sun-exposure sites, higher risks of cutaneous neoplasms and absence of classical XP features, WGS didn't find supportive genetical evidence, but 2 HERC2 variants were assigned highest suspicion in both XP and SCC by bioinformatical analyses.

INTERVENTIONS

Anti-inflammatory treatment, sunscreens and moisturizers were administered.

OUTCOMES

The daughter's cutaneous lesions developed slowly during the 6-year follow-up, but the keratitis seriously weakened her sight.

LESSONS

To our knowledge, it's the first report of cases carrying FMD, keratitis, xerosis, poikiloderma and acro-osteolysis simultaneously, and 3 likely pathogenic variants were identified. Whole genome/exon sequencing is recommended as a common test for patients with rare phenotypes.

Frontal cranioplasty in fronto-metaphyseal dysplasia

INTRODUCTION

Fronto-metaphyseal dysplasia (FMD), also called Gorlin-Cohen syndrome, is a rare syndrome initially described in 1969 by Gorlin and Cohen. Patients present skeletal dysplasia, craniofacial malformations and digit abnormalities. Craniofacial phenotype of FMD is characterized by supraorbital hyperostosis, hypertelorism, down-slanting palpebral fissures, broad nasal bridge and micrognathia. Here, we report the first adult case of craniofacial reconstruction with frontal cranioplasty in a patient with FMD.

OBSERVATION

A 21-year-old male patient presented with aesthetic requests related to his facial abnormalities. The patient underwent a fronto-orbital cranioplasty using a coronal approach. Orbital, frontal and nasal hyperostoses were contoured in order to obtain a symmetric result. The patient had no postoperative complication. Aesthetic results were satisfactory and stable after 6 months of follow-up.

DISCUSSION

The density and the quality of craniofacial bones were normal and this may account for the stability of cranioplasty results over time. Because bone was normal, cranioplasty is safety and stable in FMD.