Genotype-phenotype correlations on epidermolysis bullosa with congenital absence of skin: A comprehensive review.

Congenital absence of skin (CAS) is a clinical sign associated with the main types of epidermolysis bullosa (EB). Very few studies have investigated the genetic background that may influence the occurrence of this condition. Our objective was to investigate genotype-phenotype correlations on EB with CAS through a literature revision on the pathogenic variants previously reported. A total of 171 cases (49 EB simplex, EBS; 23 junctional EB, JEB; and 99 dystrophic EB, DEB), associated with 132 pathogenic variants in eight genes, were included in the genotype-phenotype analysis. In EBS, CAS showed to be a recurrent clinical sign in EBS with pyloric atresia (PA) and EBS associated with kelch-like protein 24; CAS was also described in patients with keratins 5/14 alterations, particularly involving severe phenotypes. In JEB, this is a common clinical sign in JEB with PA associated with premature termination codon variants and/or amino acid substitutions located in the extracellular domain of integrin α6ß4 genes. In DEB with CAS, missense variants occurring close to non-collagenous interruptions of the triple-helix domain of collagen VII appear to influence this condition. This study is the largest review of patients with EB and CAS and expands the spectrum of known variants on this phenomenon.

CHARGE syndrome patient with novel CHD7 mutation presenting with severe laryngomalacia and feeding difficulty.

We report a case of CHARGE syndrome with atypical phenotype and a novel mutation in the CHD7 gene. Laryngomalacia and swallowing difficulties are prominent features in this case. These are commonly found in patients with CHARGE syndrome and are well described in previous studies. However, with the traditional diagnostic criteria, diagnosis is difficult without the presence of coloboma or choanal atresia. Early diagnosis is possible with the aid of clinical genetics. The current diagnostic criteria would need to be broadened with the inclusion of pathogenic CHD7 variant status as a major criterion. Further research on the function of CHD7 gene may also give us more insight on the pathogenic mechanism of various clinical features of CHARGE syndrome.

Ectrodactyly-ectodermal dysplasia-clefting syndrome presenting with bilateral choanal atresia and rectal stenosis.

We present the case of a male who shortly after birth developed acute respiratory distress due to bilateral choanal atresia, following which he was found to have rectal stenosis. Genetic testing for CHARGE syndrome was negative, but whole genome sequencing identified heterozygosity for a pathogenic missense variant in TP63 (c.727C > T, p.(Arg243Trp). He also has partial cutaneous syndactyly of the third and fourth fingers of the right hand, and bilateral lacrimal duct stenosis/aplasia. A later maxillofacial review identified a palpable submucousal cleft and his scalp hair is blond and slightly sparse. Choanal atresia and rectal stenosis are recognized features of ectrodactyly-ectodermal dysplasia-clefting syndrome, but we believe this is the first report of a case presenting with these features in the absence of the cardinal features.

Spliceosomopathies and neurocristopathies: Two sides of the same coin?

Mutations in core components of the spliceosome are responsible for a group of syndromes collectively known as spliceosomopathies. Patients exhibit microcephaly, micrognathia, malar hypoplasia, external ear anomalies, eye anomalies, psychomotor delay, intellectual disability, limb, and heart defects. Craniofacial malformations in these patients are predominantly found in neural crest cells-derived structures of the face and head. Mutations in eight genes SNRPB, RNU4ATAC, SF3B4, PUF60, EFTUD2, TXNL4, EIF4A3, and CWC27 are associated with craniofacial spliceosomopathies. In this review, we provide a brief description of the normal development of the head and the face and an overview of mutations identified in genes associated with craniofacial spliceosomopathies. We also describe a model to explain how and when these mutations are most likely to impact neural crest cells. We speculate that mutations in a subset of core splicing factors lead to disrupted splicing in neural crest cells because these cells have increased sensitivity to inefficient splicing. Hence, disruption in splicing likely activates a cellular stress response that includes increased skipping of regulatory exons in genes such as MDM2 and MDM4, key regulators of P53. This would result in P53-associated death of neural crest cells and consequently craniofacial malformations associated with spliceosomopathies.

SMCHD1 mutation spectrum for facioscapulohumeral muscular dystrophy type 2 (FSHD2) and Bosma arhinia microphthalmia syndrome (BAMS) reveals disease-specific localisation of variants in the ATPase domain.

BACKGROUND: Variants in the Structural Maintenance of Chromosomes flexible Hinge Domain-containing protein 1 (SMCHD1) can cause facioscapulohumeral muscular dystrophy type 2 (FSHD2) and the unrelated Bosma arhinia microphthalmia syndrome (BAMS). In FSHD2, pathogenic variants are found anywhere in SMCHD1 while in BAMS, pathogenic variants are restricted to the extended ATPase domain. Irrespective of the phenotypic outcome, both FSHD2-associated and BAMS-associated SMCHD1 variants result in quantifiable local DNA hypomethylation. We compared FSHD2, BAMS and non-pathogenic SMCHD1 variants to derive genotype-phenotype relationships. METHODS: Examination of SMCHD1 variants and methylation of the SMCHD1-sensitive FSHD locus DUX4 in 187 FSHD2 families, 41 patients with BAMS and in control individuals. Analysis of variants in a three-dimensional model of the ATPase domain of SMCHD1. RESULTS: DUX4 methylation analysis is essential to establish pathogenicity of SMCHD1 variants. Although the FSHD2 mutation spectrum includes all types of variants covering the entire SMCHD1 locus, missense variants are significantly enriched in the extended ATPase domain. Identification of recurrent variants suggests disease-specific residues for FSHD2 and in BAMS, consistent with a largely disease-specific localisation of variants in SMCHD1. CONCLUSIONS: The localisation of missense variants within the ATPase domain of SMCHD1 may contribute to the differences in phenotypic outcome.

Familial congenital choanal atresia with GATA3 associated hypoparathyroidism-deafness-renal dysplasia syndrome unidentified on auditory brainstem response.

Hypoparathyroidism-deafness-renal dysplasia (HDR) syndrome is a rare autosomal dominant disorder primarily caused by GATA3 haploinsufficiency and is challenging to diagnose in early childhood. We report a Japanese family with HDR syndrome and congenital choanal atresia. The 6-year-old female proband was diagnosed with epilepsy at the age of three. Under carbamazepine monotherapy, the patient presented hypoparathyroidism accompanied by severe hypocalcemia. Subsequently, renal ultrasound analysis revealed bilateral multicystic dysplastic kidneys. Because she had difficulty hearing, we sequenced GATA3 and determined that she had a c.708_709insC (p.Ser237Glnfs*66) allelic variant in exon 3. As a result, we found a family of this disease. Each family member, including her grandfather, mother, and two siblings, had HDR syndrome of varying clinical penetrance. We found a craniofacial anomaly, congenital choanal atresia, which was inherited as an autosomal dominant trait. Hypocalcemia coupled with vitamin D deficiency, triggered by carbamazepine treatment, ultimately revealed the proband's childhood- onset HDR syndrome. Pure-tone audiometry revealed different severities of deafness as well as the progression of sensory hearing loss. However, auditory brainstem response for hearing screening is probably insufficient for ascertaining HDR syndrome in the early stages of life. We presented new clinical clues to diagnose the HDR syndrome.

FSHD type 2 and Bosma arhinia microphthalmia syndrome: Two faces of the same mutation.

OBJECTIVE: To determine whether congenital arhinia/Bosma arhinia microphthalmia syndrome (BAMS) and facioscapulohumeral muscular dystrophy type 2 (FSHD2), 2 seemingly unrelated disorders both caused by heterozygous pathogenic missense variants in the SMCHD1 gene, might represent different ends of a broad single phenotypic spectrum associated with SMCHD1 dysfunction. METHODS: We examined and/or interviewed 14 patients with FSHD2 and 4 unaffected family members with N-terminal SMCHD1 pathogenic missense variants to identify BAMS subphenotypes. RESULTS: None of the patients with FSHD2 or family members demonstrated any congenital defects or dysmorphic features commonly found in patients with BAMS. One patient became anosmic after nasal surgery and one patient was hyposmic; one man was infertile (unknown cause) but reported normal pubertal development. CONCLUSION: These data suggest that arhinia/BAMS and FSHD2 do not represent one phenotypic spectrum and that SMCHD1 pathogenic variants by themselves are insufficient to cause either of the 2 disorders. More likely, both arhinia/BAMS and FSHD2 are caused by complex oligogenic or multifactorial mechanisms that only partially overlap at the level of SMCHD1.

FSHD2- and BAMS-associated mutations confer opposing effects on SMCHD1 function.

Structural maintenance of chromosomes flexible hinge domain-containing 1 (Smchd1) plays important roles in epigenetic silencing and normal mammalian development. Recently, heterozygous mutations in SMCHD1 have been reported in two disparate disorders: facioscapulohumeral muscular dystrophy type 2 (FSHD2) and Bosma arhinia microphthalmia syndrome (BAMS). FSHD2-associated mutations lead to loss of function; however, whether BAMS is associated with loss- or gain-of-function mutations in SMCHD1 is unclear. Here, we have assessed the effect of SMCHD1 missense mutations from FSHD2 and BAMS patients on ATP hydrolysis activity and protein conformation and the effect of BAMS mutations on craniofacial development in a Xenopus model. These data demonstrated that FSHD2 mutations only result in decreased ATP hydrolysis, whereas many BAMS mutations can result in elevated ATPase activity and decreased eye size in Xenopus Interestingly, a mutation reported in both an FSHD2 patient and a BAMS patient results in increased ATPase activity and a smaller Xenopus eye size. Mutations in the extended ATPase domain increased catalytic activity, suggesting critical regulatory intramolecular interactions and the possibility of targeting this region therapeutically to boost SMCHD1's activity to counter FSHD.

Choanal Atresia and Craniosynostosis: Development and Disease.

A number of textbooks, review articles, and case reports highlight the potential comorbidity of choanal atresia in craniosynostosis patients. However, the lack of a precise definition of choanal atresia within the current craniosynostosis literature and widely varying methods of detection and diagnosis have produced uncertainty regarding the true coincidence of these conditions. The authors review the anatomy and embryologic basis of the human choanae, provide an overview of choanal atresia, and analyze the available literature that links choanal atresia and craniosynostosis. Review of over 50 case reports that describe patients diagnosed with both conditions reveals inconsistent descriptions of choanal atresia and limited use of definitive diagnostic methodologies. The authors further present preliminary analysis of three-dimensional medical head computed tomographic scans of children diagnosed with craniosynostosis syndromes (e.g., Apert, Pfeiffer, Muenke, and Crouzon) and typically developing children and, although finding no evidence of choanal atresia, report the potentially reduced nasal airway volumes in children diagnosed with Apert and Pfeiffer syndromes. A recent study of the Fgfr2c Crouzon/Pfeiffer syndrome mouse model similarly found a significant reduction in nasal airway volumes in littermates carrying this FGFR2 mutation relative to unaffected littermates, without detection of choanal atresia. The significant correlation between specific craniosynostosis syndromes and reduced nasal airway volume in mouse models for craniosynostosis and human pediatric patients indicates comorbidity of choanal and nasopharyngeal dysmorphologies and craniosynostosis conditions. Genetic, developmental, and epidemiologic sources of these interactions are areas particularly worthy of further research.

Clinical delineation of a subtype of frontonasal dysplasia with creased nasal ridge and upper limb anomalies: Report of six unrelated patients.

Frontonasal dysplasias are rare congenital malformations of frontonasal process-derived structures, characterized by median cleft, nasal anomalies, widely spaced eyes, and cranium bifidum occultum. Several entities of syndromic frontonasal dysplasia have been described, among which, to date, only a few have identified molecular bases. We clinically ascertained a cohort of 124 individuals referred for frontonasal dysplasia. We identified six individuals with a similar phenotype, including one discordant monozygous twin. Facial features were remarkable by nasal deformity with creased ridge and depressed or absent tip, widely spaced eyes, almond-shaped palpebral fissures, and downturned corners of the mouth. All had apparently normal psychomotor development. In addition, upper limb anomalies, frontonasal encephalocele, corpus callosum agenesis, choanal atresia, and congenital heart defect were observed. We identified five reports in the literature of patients presenting with the same phenotype. Exome sequencing was performed on DNA extracted from blood of two individuals, no candidate gene was identified. In conclusion, we report six novel simplex individuals presenting with a specific frontonasal dysplasia entity associating recognizable facial features, limb and visceral malformations, and apparently normal development. The identification of discordant monozygotic twins supports the hypothesis of a mosaic disorder. Although previous patients have been reported, this is the first series, allowing delineation of a clinical subtype of frontonasal dysplasia, paving the way toward the identification of its molecular etiology.

KMT2D p.Gln3575His segregating in a family with autosomal dominant choanal atresia strengthens the Kabuki/CHARGE connection.

Choanal atresia is rarely reported in Kabuki syndrome, but is a common feature of CHARGE syndrome. Otherwise, the two conditions have a number of overlapping features, and the molecular links between them have recently been elucidated. Here, we report a case of a mother and her two children who presented with congenital choanal atresia. We performed whole exome sequencing on DNA from the mother and her two unaffected parents, and identified a de novo, novel variant in KMT2D. KMT2D p.Gln3575His segregated with disease status in the family, and is associated with a unique and conserved phenotype in the affected family members, with features overlapping with Kabuki and CHARGE syndromes. Our findings further support the potential etiological link between these two classically distinct conditions. © 2016 Wiley Periodicals, Inc.

Compound heterozygosity of low-frequency promoter deletions and rare loss-of-function mutations in TXNL4A causes Burn-McKeown syndrome.

Mutations in components of the major spliceosome have been described in disorders with craniofacial anomalies, e.g., Nager syndrome and mandibulofacial dysostosis type Guion-Almeida. The U5 spliceosomal complex of eight highly conserved proteins is critical for pre-mRNA splicing. We identified biallelic mutations in TXNL4A, a member of this complex, in individuals with Burn-McKeown syndrome (BMKS). This rare condition is characterized by bilateral choanal atresia, hearing loss, cleft lip and/or palate, and other craniofacial dysmorphisms. Mutations were found in 9 of 11 affected families. In 8 families, affected individuals carried a rare loss-of-function mutation (nonsense, frameshift, or microdeletion) on one allele and a low-frequency 34 bp deletion (allele frequency 0.76%) in the core promoter region on the other allele. In a single highly consanguineous family, formerly diagnosed as oculo-oto-facial dysplasia, the four affected individuals were homozygous for a 34 bp promoter deletion, which differed from the promoter deletion in the other families. Reporter gene and in vivo assays showed that the promoter deletions led to reduced expression of TXNL4A. Depletion of TXNL4A (Dib1) in yeast demonstrated reduced assembly of the tri-snRNP complex. Our results indicate that BMKS is an autosomal-recessive condition, which is frequently caused by compound heterozygosity of low-frequency promoter deletions in combination with very rare loss-of-function mutations.

Osteosclerotic bone dysplasia in siblings with a Fam20C mutation.

Raine syndrome is an autosomal recessive disorder caused by mutations in the FAM20C gene. FAM20C codes for the human homolog of DMP4, a dentin matrix protein highly expressed in odontoblasts and moderately in bone. DMP4 is probably playing a role in the mineralization process. Since the first case reported in 1989 by Raine et al. 21 cases have been published delineating a phenotype which associates dysmorphic features, cerebral calcifications, choanal atresia or stenosis and thoracic/pulmonary hypoplasia. Kan and Kozlowski suggested the name of Raine syndrome to describe this new lethal osteosclerotic bone dysplasia. All the cases described were lethal during the neonatal period except for the last two reported patients aged 8 and 11 years who presented severe mental retardation. Here we describe two sisters, with an attenuated phenotype of Raine syndrome, who present an unexpectedly normal psychomotor development at ages 4 and 1, respectively. Identification of a homozygous mutation in the FAM20C gene confirmed the Raine syndrome diagnosis, thus contributing to the expansion of the Raine syndrome phenotype. This case report also prompted us to revisit the FAM20 gene classification and allowed us to highlight the ancestral status of Fam20C.

Protein tyrosine phosphatase PTPN14 is a regulator of lymphatic function and choanal development in humans.

The lymphatic vasculature is essential for the recirculation of extracellular fluid, fat absorption, and immune function and as a route of tumor metastasis. The dissection of molecular mechanisms underlying lymphangiogenesis has been accelerated by the identification of tissue-specific lymphatic endothelial markers and the study of congenital lymphedema syndromes. We report the results of genetic analyses of a kindred inheriting a unique autosomal-recessive lymphedema-choanal atresia syndrome. These studies establish linkage of the trait to chromosome 1q32-q41 and identify a loss-of-function mutation in PTPN14, which encodes a nonreceptor tyrosine phosphatase. The causal role of PTPN14 deficiency was confirmed by the generation of a murine Ptpn14 gene trap model that manifested lymphatic hyperplasia with lymphedema. Biochemical studies revealed a potential interaction between PTPN14 and the vascular endothelial growth factor receptor 3 (VEGFR3), a receptor tyrosine kinase essential for lymphangiogenesis. These results suggest a unique and conserved role for PTPN14 in the regulation of lymphatic development in mammals and a nonconserved role in choanal development in humans.

Microcephaly, microtia, preauricular tags, choanal atresia and developmental delay in three unrelated patients: a mandibulofacial dysostosis distinct from Treacher Collins syndrome.

Treacher Collins syndrome (TCS, OMIM 154500) is a well-defined mandibulofacial dysostosis characterized by symmetric facial anomalies consisting of malar hypoplasia, coloboma of the lower eyelid, dysplastic ears, micrognathia, cleft palate and deafness. Other mandibulofacial dysostoses (MDs) such as Toriello (OMIM 301950), Bauru (OMIM 604830), Hedera-Toriello-Petty (OMIM 608257), and Guion-Almeida (OMIM 610536) syndromes are less well characterized and much rarer. Here we describe three unrelated patients showing clinical features overlapping with TCS, but who in addition have developmental delay, microcephaly and a distinct facial gestalt. Because of the distinct ear anomalies and the hearing loss a HOXA2 mutation was taken into account. CHARGE syndrome was discussed because of ear anomalies, choanal atresia, and developmental delay in our patients. But mutational analyses including sequencing of the TCOF1, the HOXA2, and the CHD7 genes, deletion screening of the TCOF1 gene as well as genomewide array analyses revealed normal results. We suggest that these three patients have a new type of mandibulofacial dysostosis. As all three cases are sporadic and both sexes are affected the pattern of inheritance might be autosomal dominant or autosomal recessive. Identification of additional patients will allow to further delineate the phenotype, to assign the inheritance pattern and to identify the molecular basis.

New recognized ophthalmic morphologic anomalies in CHARGE syndrome caused by the R2319C mutation in the CHD7 gene.

PURPOSE: To report new findings in the CHARGE syndrome with phenotypic anomalies associated with the R2319C mutation in the CHD7 gene. METHODS: Fundoscopic photography, ultrasonography, fluorescein angiography, optical coherence tomography (OCT). Mutational analysis of the CHD7 gene in lymphocyte DNA. RESULTS: Large pale optic discs with a fibrous elevation and colobomata and arterio-venous anastomoses with enlarged veins in optic discs were detected. OCT revealed numerous flat cystic spaces. The genetic study revealed the R2319C mutation in the CHD7 gene. CONCLUSIONS: The CHARGE syndrome associated with the R2319C mutation in the CHD7 gene comprised: cystic spaces in the colobomatous optic disc and intrapapillary arterio-venous anastomoses.

Solitary median maxillary central incisor (SMMCI) syndrome.

Solitary median maxillary central incisor syndrome (SMMCI) is a complex disorder consisting of multiple, mainly midline defects of development resulting from unknown factor(s) operating in utero about the 35th-38th day(s) from conception. It is estimated to occur in 1:50,000 live births. Aetiology is uncertain. Missense mutation in the SHH gene (I111F) at 7q36 may be associated with SMMCI. The SMMCI tooth differs from the normal central incisor, in that the crown form is symmetric; it develops and erupts precisely in the midline of the maxillary dental arch in both primary and permanent dentitions. Congenital nasal malformation (choanal atresia, midnasal stenosis or congenital pyriform aperture stenosis) is positively associated with SMMCI. The presence of an SMMCI tooth can predict associated anomalies and in particular the serious anomaly holoprosencephaly. Common congenital anomalies associated with SMMCI are: severe to mild intellectual disability, congenital heart disease, cleft lip and/or palate and less frequently, microcephaly, hypopituitarism, hypotelorism, convergent strabismus, oesophageal and duodenal atresia, cervical hemivertebrae, cervical dermoid, hypothyroidism, scoliosis, absent kidney, micropenis and ambiguous genitalia. Short stature is present in half the children. Diagnosis should be made by eight months of age, but can be made at birth and even prenatally at 18-22 weeks from the routine mid-trimester ultrasound scan. Management depends upon the individual anomalies present. Choanal stenosis requires emergency surgical treatment. Short stature may require growth hormone therapy. SMMCI tooth itself is mainly an aesthetic problem, which is ideally managed by combined orthodontic, prosthodontic and oral surgical treatment; alternatively, it can be left untreated.

Characteristics of lacrimo-auriculo-dento-digital (LADD) syndrome: case report of a family and literature review.

We describe a family with lacrimo-auriculo-dento-digital syndrome (LADD). A 13-year-old boy had cup-shaped ears, deafness, unilateral choanal atresia, bilateral nasolacrimal duct obstruction, xerostomia, alacrima due to congenital absence of lacrimal glands, agenesis of salivary glands, chronic dacryocystitis, keratoconjunctivitis sicca, ptosis, nail dysplasia of the thumb, shortness of fifth toe, temporal bone abnormality and epilepsy. His younger sister had shortened middle phalanx of fifth digits. His middle sister had hypodontia, shortened distal phalanx of fifth digit, agenesis of salivary glands, mild hearing loss and exotropia. His older sister had left nasolacrimal duct obstruction and aplasia of both parotid glands. The oldest sister had hypodontia and divergent excess exotropia. His mother had hypodontia. These findings are consistent with LADD syndrome. An autosomal dominant pattern of inheritance with variable expressivity has been demonstrated. Renal and uro-genital anomalies have been noted variably.