Familial cerebro-costo-mandibular syndrome: a case with unusual prenatal findings and review

Cerebrocostomandibular syndrome: a diagnostic challenge

A male infant born in a tertiary maternity facility was noted to have microretrognathia, a small mouth and macroglossia at delivery. He was born limp and apnoeic and required multiple attempts at intubation before a definitive airway was eventually sited. Chest X-rays, while in the paediatric intensive care unit, demonstrated dysplastic ribs with associated 'high-riding' clavicles. A later X-ray was reported as showing interrupted posterior ribs. A tracheostomy was formed on day of life 9 given the immediate risk to the baby's airway. Further imaging of the facial bones, skull and brain showed generous CSF spaces over the cerebral convexities and also marked hypoplasia of the mandible and mid-face. The baby's middle ear cavities were shown to be completely opacified. Genetic testing eventually went on to confirm a diagnosis of cerebrocostomandibular syndrome, with the detection of a pathogenic variant of the small nuclear ribonucleoprotein polypeptide B gene.

Alternative splicing: Human disease and quantitative analysis from high-throughput sequencing

Alternative splicing contributes to the majority of protein diversity in higher eukaryotes by allowing one gene to generate multiple distinct protein isoforms. It adds another regulation layer of gene expression. Up to 95% of human multi-exon genes undergo alternative splicing to encode proteins with different functions. Moreover, around 15% of human hereditary diseases and cancers are associated with alternative splicing. Regulation of alternative splicing is attributed to a set of delicate machineries interacting with each other in aid of important biological processes such as cell development and differentiation. Given the importance of alternative splicing events, their accurate mapping and quantification are paramount for downstream analysis, especially for associating disease with alternative splicing. However, deriving accurate isoform expression from high-throughput RNA-seq data remains a challenging task. In this mini-review, we aim to illustrate I) mechanisms and regulation of alternative splicing, II) alternative splicing associated human disease, III) computational tools for the quantification of isoforms and alternative splicing from RNA-seq.

snRNP proteins in health and disease

Split gene architecture of most human genes requires removal of intervening sequences by mRNA splicing that occurs on large multiprotein complexes called spliceosomes. Mutations compromising several spliceosomal components have been recorded in degenerative syndromes and haematological neoplasia, thereby highlighting the importance of accurate splicing execution in homeostasis of assorted adult tissues. Moreover, insufficient splicing underlies defective development of craniofacial skeleton and upper extremities. This review summarizes recent advances in the understanding of splicing factor function deduced from cryo-EM structures. We combine these data with the characterization of splicing factors implicated in hereditary or somatic disorders, with a focus on potential functional consequences the mutations may elicit in spliceosome assembly and/or performance. Given aberrant splicing or perturbations in splicing efficiency substantially underpin disease pathogenesis, profound understanding of the mis-splicing principles may open new therapeutic vistas. In three major sections dedicated to retinal dystrophies, hereditary acrofacial syndromes, and haematological malignancies, we delineate the noticeable variety of conditions associated with dysfunctional splicing and accentuate recurrent patterns in splicing defects.

Cerebro-costo-mandibular syndrome: Clinical, radiological, and genetic findings

Cerebro-Costo-Mandibular syndrome (CCMS) is a rare autosomal dominant condition comprising branchial arch-derivative malformations with striking rib-gaps. Affected patients often have respiratory difficulties, associated with upper airway obstruction, reduced thoracic capacity, and scoliosis. We describe a series of 12 sporadic and 4 familial patients including 13 infants/children and 3 adults. Severe micrognathia and reduced numbers of ribs with gaps are consistent findings. Cleft palate, feeding difficulties, respiratory distress, tracheostomy requirement, and scoliosis are common. Additional malformations such as horseshoe kidney, hypospadias, and septal heart defect may occur. Microcephaly and significant developmental delay are present in a small minority of patients. Key radiological findings are of a narrow thorax, multiple posterior rib gaps and abnormal costo-transverse articulation. A novel finding in 2 patients is bilateral accessory ossicles arising from the hyoid bone. Recently, specific mutations in SNRPB, which encodes components of the major spliceosome, have been found to cause CCMS. These mutations cluster in an alternatively spliced regulatory exon and result in altered SNRPB expression. DNA was available from 14 patients and SNRPB mutations were identified in 12 (4 previously reported). Eleven had recurrent mutations previously described in patients with CCMS and one had a novel mutation in the alternative exon. These results confirm the specificity of SNRPB mutations in CCMS and provide further evidence for the role of spliceosomal proteins in craniofacial and thoracic development.

A review of craniofacial disorders caused by spliceosomal defects

The spliceosome is a large ribonucleoprotein complex that removes introns from pre-mRNA transcripts. Mutations in EFTUD2, encoding a component of the major spliceosome, have recently been identified as the cause of mandibulofacial dysostosis, Guion-Almeida type (MFDGA), characterized by mandibulofacial dysostosis, microcephaly, external ear malformations and intellectual disability. Mutations in several other genes involved in spliceosomal function or linked aspects of mRNA processing have also recently been identified in human disorders with specific craniofacial malformations: SF3B4 in Nager syndrome, an acrofacial dysostosis (AFD); SNRPB in cerebrocostomandibular syndrome, characterized by Robin sequence and rib defects; EIF4A3 in the AFD Richieri-Costa-Pereira syndrome, characterized by Robin sequence, median mandibular cleft and limb defects; and TXNL4A in Burn-McKeown syndrome, involving specific craniofacial dysmorphisms. Here, we review phenotypic and molecular aspects of these syndromes. Given the apparent sensitivity of craniofacial development to defects in mRNA processing, it is possible that mutations in other proteins involved in spliceosomal function will emerge in the future as causative for related human disorders.

Ex utero intrapartum treatment for an infant with cerebro-costo-mandibular syndrome

Cerebro-costo-mandibular syndrome (CCMS) is a rare disorder characterized by multiple rib abnormalities, micrognathia described as Pierre-Robin sequence, and cerebral involvement. Appropriate management of respiratory distress immediately after birth is crucial to rescue these patients. A boy, having a mother with Pierre-Robin sequence and a sister with CCMS, was diagnosed prenatally with CCMS and successfully treated with ex utero intrapartum treatment (EXIT) at 36 weeks 6 days of gestation. EXIT would be an effective option for rescuing patients with prenatally diagnosed CCMS and preventing neonatal hypoxia.

Cerebro-costo-mandibular syndrome: prognosis and proposal for classification

Cerebro-costo-mandibular syndrome (CCMS) is a very rare syndrome characterized by micrognathia and posterior rib gap, with a poor prognosis. To date, only 75 cases have been reported worldwide. The overall survival rate for patients with this disorder has not been reported, and a classification of the patients on the basis of the prognosis is not yet available. The present study analyzed the figures and prognoses of past patients and documented a new case of CCMS. Formerly published case reports and personal communications were used to reveal the prognosis and classification of CCMS. The occurrence ratios of rib gap defects and of missing ribs were examined. Patients were divided into the following three groups according to their life span: lethal type, where the patients died before 1 month; severe type, where the patients lived for 1-12 months; and mild type, where they survived for more than 1 year. A comparison was made of the number of rib gaps, missing ribs, and the rib gap ratio (defined as the number of rib gaps divided by the number of all existing ribs) among these three groups. A significant difference in the number of rib defects between the lethal type and other types was noted. Short life span of severe type patients, compared to mild type, was attributed to their subjection to severe respiratory infection. CCMS can be classified into three categories--lethal, severe, and mild--according to the severity of the symptoms and prognosis.

Exclusion of MYF5, GSC, RUNX2, and TCOF1 mutation in a case of cerebro-costo-mandibular syndrome

Cerebro-costo-mandibular syndrome (CCMS) is an uncommon multiple congenital anomaly syndrome characterized by severe micrognathia, posterior rib-gap defects, and developmental delay. The cause of CCMS is unknown. Genes hypothesized to have a causal role in CCMS, include myogenic factor 5 (MYF5), goosecoid homeobox (GSC) and runt-related transcription factor 2 (RUNX2) [formerly known as core-binding factor (CBFA1)]. We report an infant with typical features of CCMS who, on prenatal ultrasound, was found to have severe micrognathia. We present the first image by three-dimensional computed tomography of posterior rib-defect, and we exclude mutations of the MYF5, GSC, RUNX2, and TCOF1 genes in our patient. Further molecular studies are needed to evaluate the cause of CCMS.

Successful weaning of a laryngeal mask airway after a tongue-lip adhesion operation in a case with cerebro-costo-mandibular syndrome

Cerebro-costo-mandibular syndrome (CCMS) consists of severe micrognathia, glossoptosis, posterior rib-gap defects and developmental delay. It may cause upper airway obstruction andflail chest, resulting in neonatal hypoxia, and possibly death. Early airway management or surgical intervention to maintain a patent airway is critical to avoid hypoxia in CCMS patients. We report a newborn with CCMS who was successfully weaned from a laryngeal mask after undergoing a tongue-lip adhesion operation at 164 days of age.

Spine deformities in rare congenital syndromes: clinical issues

STUDY DESIGN

A focused review of the literature with regard to the important system abnormalities of patients with spinal deformities associated with exotic congenital syndromes with additional data from the author's own experience in assessment of patients with rare syndromes treated for thoracic insufficiency syndrome.

OBJECTIVES

The objectives of this study are to emphasize important medical considerations that influence the choice of surgical treatment of spinal deformity in patients with exotic congenital syndromes and point out preoperative strategies that reduce treatment morbidity and mortality of these patients.

SUMMARY OF BACKGROUND DATA

Individual experience is limited in the treatment of spine abnormality in rare exotic syndromes and the medical aspects of these syndromes that may impact spinal treatment are seldom discussed in detail in the orthopedic literature. For a successful outcome in the treatment of spinal deformity in these unique patients, a working knowledge of the unique pitfalls in their medical care is necessary in order to avoid morbidity and mortality during their treatment.

METHODS

The literature was reviewed for 6 exotic congenital syndromes with known or unreported spinal abnormalities and the author's personal 22-years experience of the treatment of thoracic insufficiency syndrome in the relevant congenital syndromes was summarized.

RESULTS

Children with Marfan syndrome and spinal deformity may have serious cardiac abnormalities. Spontaneous dissection of the aortic root is a clear danger and patients should be monitored by serial echocardiograms. Prophylactic cardiac surgery may be necessary before spinal surgery is to be performed. Patients with Jeune syndrome have a high rate of proximal cervical stenosis and should undergo screening with cervical spine films at birth. Significant stenosis or instability may require decompression and cervical-occipital fusion. Arthrogryposis may be associated with a severe scoliosis and jaw contracture may make intubation difficult. Larsen syndrome may have early onset scoliosis that is very rigid and requires early intervention. Cervical kyphosis and subluxation may be lethal in these patients and screening radiographs are important. Upper airway abnormalities are an anesthesia concern. Jarcho-Levin syndrome is a thoracic volume depletion deformity due to shortness of the thorax, either a spondylocostal dysostosis variant or spondylothoracic dysplasia. The former has a chaotic congenital scoliosis with varied combination of missing and fused ribs. Although spondylocostal dysostosis has a benign reputation in the literature for respiratory complications, respiratory insufficiency is nevertheless common and 1 death is known from respiratory failure. Spondylothoracic dysplasia seldom has significant scoliosis, but has a mortality rate approaching 50% from respiratory complications due to thoracic insufficiency syndrome. In spite of severe restrictive respiratory disease, adult survivors of spondylothoracic dysplasia appear to do well clinically for unknown reasons. Cerebrocostomandibular syndrome has scoliosis, micrognathia, and thoracic insufficiency syndrome, due to an "implosion" deformity of the thorax from congenital pseudarthrosis of the posterior ribs.

CONCLUSION

For optimal patient care, it is necessary to have a clear understanding of exotic congenital syndromes and how they may impact on both the presentation of spinal deformity and the response to treatment, as well as how they may introduce additional morbidity into standard treatment plans. It is clear that with this understanding that preoperative strategies can be employed to enhance the safety of spinal treatment for these unique children.

Cerebrocostomandibular-like syndrome and a mutation in the conserved oligomeric Golgi complex, subunit 1

We describe two patients with a cerebrocostomandibular-like syndrome and a novel mutation in conserved oligomeric Golgi (COG) subunit 1, one of the subunits of the conserved oligomeric Golgi complex. This hetero-octameric protein complex is involved in retrograde vesicular trafficking and glycosylation. We identified in both patients an intronic mutation, c.1070+5G>A, that disrupts a splice donor site and leads to skipping of exon 6, a frameshift and a premature stopcodon in exon 7. Real-time reverse transcriptase polymerase chain reaction showed in the first patient only 3% of normal transcript when compared with control. A delay in retrograde trafficking could be demonstrated by Brefeldin A treatment of this patient's fibroblasts. The costovertebral dysplasia of the two patients has been described in cerebrocostomandibular syndrome (CCMS), but also in cerebrofaciothoracic dysplasia and spondylocostal dysostosis. CCMS itself is heterogeneous because both autosomal dominant and autosomal recessive inheritance has been described. We anticipate further genetic heterogeneity because no mutations in COG1 were found in two additional patients with a CCMS.

Syndromes and Disorders Associated with Omphalocele (III): Single Gene Disorders, Neural Tube Defects, Diaphragmatic Defects and Others

Omphalocele can be associated with single gene disorders, neural tube defects, diaphragmatic defects, fetal valproate syndrome, and syndromes of unknown etiology. This article provides a comprehensive review of omphalocele-related disorders: otopalatodigital syndrome type II; Melnick-Needles syndrome; Rieger syndrome; neural tube defects; Meckel syndrome; Shprintzen-Goldberg omphalocele syndrome; lethal omphalocele-cleft palate syndrome; cerebro-costo-mandibular syndrome; fetal valproate syndrome; Marshall-Smith syndrome; fibrochondrogenesis; hydrolethalus syndrome; Fryns syndrome; omphalocele, diaphragmatic defects, radial anomalies and various internal malformations; diaphragmatic defects, limb deficiencies and ossification defects of skull; Donnai-Barrow syndrome; CHARGE syndrome; Goltz syndrome; Carpenter syndrome; Toriello-Carey syndrome; familial omphalocele; Cornelia de Lange syndrome; C syndrome; Elejalde syndrome; Malpuech syndrome; cervical ribs, Sprengel anomaly, anal atresia and urethral obstruction; hydrocephalus with associated malformations; Kennerknecht syndrome; lymphedema, atrial septal defect and facial changes; and craniosynostosismental retardation syndrome of Lin and Gettig. Perinatal identification of omphalocele should alert one to the possibility of omphalocele-related disorders and familial inheritance and prompt a thorough genetic counseling for these disorders.