Identification of bi-allelic LFNG variants in three patients and further clinical and molecular refinement of spondylocostal dysostosis 3

Spondylocostal dysostosis (SCD), a condition characterized by multiple segmentation defects of the vertebrae and rib malformations, is caused by bi-allelic variants in one of the genes involved in the Notch signaling pathway that tunes the "segmentation clock" of somitogenesis: DLL3, HES7, LFNG, MESP2, RIPPLY2, and TBX6. To date, seven individuals with LFNG variants have been reported in the literature. In this study we describe two newborns and one fetus with SCD, who were found by trio-based exome sequencing (trio-ES) to carry homozygous (c.822-5C>T) or compound heterozygous (c.[863dup];[1063G>A]) and (c.[521G>T];[890T>G]) variants in LFNG. Notably, the c.822-5C>T change, affecting the polypyrimidine tract of intron 5, is the first non-coding variant reported in LFNG. This study further refines the clinical and molecular features of spondylocostal dysostosis 3 and adds to the numerous investigations supporting the usefulness of trio-ES approach in prenatal and neonatal settings.

Clinical heterogeneity of NADSYN1-associated VCRL syndrome

The NADSYN1 gene [MIM*608285] encodes the NAD synthetase 1 enzyme involved in the final step of NAD biosynthesis, crucial for cell metabolism and organ embryogenesis. Perturbating the role of NAD biosynthesis results in the association of vertebral, cardiac, renal, and limb anomalies (VCRL). This condition was initially characterized as severe with perinatal lethality or developmental delay and complex malformations in alive cases. Sixteen NADSYN1-associated patients have been published so far. This study illustrates the wide phenotypic variability in NADSYN1-associated NAD deficiency disorder. We report the clinical and molecular findings in three novel cases, two of them being siblings with the same homozygous variant and presenting with either a very severe prenatal lethal or a mild phenotypic form. In addition to an exhaustive literature, we validate the expansion of the spectrum of NAD deficiency disorder. Our findings indicate that NAD deficiency disorder should be suspected not only in the presence of the full spectrum of VCRL, but even a single of the aforementioned organs is affected. Decreased plasmatic levels of NAD should then strongly encourage the screening for any of the genes responsible for a NAD deficiency disorder.

Case report: Abdominal hernia repair using a surgical wire and an autologous omental graft in a Japanese Black calf

Background

Hernia formation is a well-known abdominal wall disorder in calves and most often occurs in the umbilical region. In addition, it occurs in the abdominal wall outside the umbilical region. It has been reported to involve acquired factors, such as external force to the lower or lateral abdominal wall, trauma, muscle weakness, and, although rare, congenital or hereditary factors. Although there have been reports on the repair of abdominal wall hernias caused by abnormal muscle formation, there have been no reports on the treatment of abdominal wall hernias caused by abnormal vertebral and rib formation in cattle or other ruminants. In this study, for the first time, we describe a case of successful closure of a hernia in the left flank caused by malformation of the vertebrae and ribs. The repair was performed by narrowing the ribs using a surgical wire and covering the defect with a free omental graft.

Case presentation

A male Japanese Black calf showed a mild bulge of the left abdominal wall and abnormal morphology of the left ribs immediately after birth. At 3 months of age, computed tomography revealed fusion of the 9th, 10th, and 11th thoracic vertebrae and missing formation of the 10th and 11th left ribs at the thoracic vertebral fusion site. Additionally, a 15.2 × 24.4 cm abdominal hernia had formed in the abdominal wall. During surgery, the ribs forming the hernia were narrowed with a surgical wire, and the hernia was covered with a large autologous free omental graft to prevent intra-abdominal organ prolapse. At the monthly follow-up (11 months after surgery), the calf had developed similarly to other calves of the same age on the farm, and no complications were noted.

Conclusions

The current case shows that a combination of rib correction using a surgical wire combined with transplantation of a free autologous greater omentum graft was shown to be a possible treatment option for surgical repair of large abdominal wall hernias caused by rib malformation.

Altered Cogs of the Clock: Insights into the Embryonic Etiology of Spondylocostal Dysostosis

Spondylocostal dysostosis (SCDO) is a rare heritable congenital condition, characterized by multiple severe malformations of the vertebrae and ribs. Great advances were made in the last decades at the clinical level, by identifying the genetic mutations underlying the different forms of the disease. These were matched by extraordinary findings in the Developmental Biology field, which elucidated the cellular and molecular mechanisms involved in embryo body segmentation into the precursors of the axial skeleton. Of particular relevance was the discovery of the somitogenesis molecular clock that controls the progression of somite boundary formation over time. An overview of these concepts is presented, including the evidence obtained from animal models on the embryonic origins of the mutant-dependent disease. Evidence of an environmental contribution to the severity of the disease is discussed. Finally, a brief reference is made to emerging in vitro models of human somitogenesis which are being employed to model the molecular and cellular events occurring in SCDO. These represent great promise for understanding this and other human diseases and for the development of more efficient therapeutic approaches.

Congenital cervical spine malformation due to bi-allelic RIPPLY2 variants in spondylocostal dysostosis type 6

RIPPLY2 is an essential part of the formation of somite patterning during embryogenesis and in establishment of rostro-caudal polarity. Here, we describe three individuals from two families with compound-heterozygous variants in RIPPLY2 (NM_001009994.2): c.238A > T, p.(Arg80*) and c.240-4 T > G, p.(?), in two 15 and 20-year-old sisters, and a homozygous nonsense variant, c.238A > T, p.(Arg80*), in an 8 year old boy. All patients had multiple vertebral body malformations in the cervical and thoracic region, small or absent rib involvement, myelopathies, and common clinical features of SCDO6 including scoliosis, mild facial asymmetry, spinal spasticity and hemivertebrae. The nonsense variant can be classified as likely pathogenic based on the ACMG criteria while the splice variants must be classified as a variant of unknown significance. With this report on two further families, we confirm RIPPLY2 as the gene for SCDO6 and broaden the phenotype by adding myelopathy with or without spinal canal stenosis and spinal spasticity to the symptom spectrum.

An In Vitro Human Segmentation Clock Model Derived from Embryonic Stem Cells

Defects in somitogenesis result in vertebral malformations at birth known as spondylocostal dysostosis (SCDO). Somites are formed with a species-specific periodicity controlled by the “segmentation clock,” which comprises a group of oscillatory genes in the presomitic mesoderm. Here, we report that a segmentation clock model derived from human embryonic stem cells shows many hallmarks of the mammalian segmentation clock in vivo, including a dependence on the NOTCH and WNT signaling pathways. The gene expression oscillations are highly synchronized, displaying a periodicity specific to the human clock. Introduction of a point of mutation into HES7, a specific mutation previously associated with clinical SCDO, eliminated clock gene oscillations, successfully reproducing the defects in the segmentation clock. Thus, we provide a model for studying the previously inaccessible human segmentation clock to better understand the mechanisms contributing to congenital skeletal defects.

The segmentation clock is a molecular oscillator regulating the tempo of somite formation in a species-specific manner. Chu et al. report an embryonic-stem-cell-derived model system displaying a human-specific gene oscillation periodicity, which can shed light on human somitogenesis and model skeletal developmental disorders.

Butterfly Vertebrae: A Systematic Review of the Literature and Analysis

STUDY DESIGN

Systematic review (Level 4).

OBJECTIVE

To summarize the demographics, clinical presentations, and conditions associated with butterfly vertebrae.

METHODS

A systematic search was performed of multiple databases. A total of 279 articles were identified for screening. Case series or case reports of butterfly vertebrae with adequate clinical detail were complied.

RESULTS

Eighty-two total articles (109 patients) were selected for final inclusion. Sixty-one percent of patients presented with a single butterfly vertebra, while 39% were multiple. The most common location for butterfly vertebrae was T1. Fifty-six percent of cases were associated with a syndrome, the most common being spondylocostal dysostosis. The presence of multiple butterfly vertebra was strongly associated with a syndrome or additional anomalies (P < .001). Overall, the most common presenting complaint was low back pain. Seventy percent of patients had associated spinal disease. Other organ systems affected included musculoskeletal (43%), craniofacial (30%), neurologic (27%), cardiovascular (24%), genitourinary (23%), gastrointestinal (22%), laboratory abnormality (16%), and endocrine (9%).

CONCLUSIONS

This study is the largest collection of butterfly vertebrae cases to date. Butterfly vertebrae are associated with spinal deformity and multiple butterfly vertebrae may indicate a syndromic illness. Low back pain or disc herniation may occur with lumbar butterfly vertebrae however the etiology of this phenomena has not been rigorously explained. Many diseases and syndromes are associated with butterfly vertebrae.

Screening of known disease genes in congenital scoliosis

Background

Congenital scoliosis (CS) is defined as a lateral curvature of the spine due to the vertebral malformations and has an incidence of 0.5–1/1,000 births. We previously examined TBX6 in Japanese CS patients and revealed that approximately 10% of CS was caused by TBX6 mutations. However, the genetic cause of remaining CS is unknown.

Methods

We recruited 78 CS patients without TBX6 mutations and major comorbidities, and investigated the genes previously reported to be associated with CS and congenital vertebral malformations by whole‐exome sequencing.

Results

We identified the compound heterozygous missense variants in LFNG in one patient. No likely disease‐causing variants were identified in other patients, however. LFNG encodes a GlcNAc‐transferase. The LFNG variants showed loss of their enzyme function.

Conclusions

A LFNG mutation is reported in a case of spondylocostal dysostosis (SCD), a skeletal dysplasia with severe malformations of vertebra and rib. The CS patient with LFNG mutations had multiple vertebral malformations including hemivertebrae, butterfly vertebrae, and block vertebrae, and rib malformations. LFNG mutations may cause a spectrum of phenotypes including CS and SCD. The current list of known disease genes could explain only a small fraction of genetic cause of CS.

Lipomeningomyelocele with Fatty Filum Terminale in a Patient with Jarcho-Levin Syndrome: A Rare Association Requiring Special Attention

Lipomeningomyelocele (LMMC) with Jarcho–Levin syndrome (JLS) is extremely rare. The syndromic association is one of LMMC with JLS is one of phenotype of spondylocostal dysostosis (SCD). SCD is an autosomal-recessive disorder characterized by defects in the vertebrae and abnormalities of the ribs in the form of segmental fusion, malalignment, or absence of a few ribs. These patients are prone to pulmonary insufficiency and repeated infections. Close anesthetic vigil is also needed to maintain optimal ventilation during surgery. We are reporting a case of 11-month-old male child presented with LMMC swelling and absent left-side multiple ribs. On further evaluation, we found hemivertebrae and scoliosis. This report highlights the experience of operating a child with JLS in prone position.

Autosomal recessive variations of TBX6, from congenital scoliosis to spondylocostal dysostosis

Proximal 16p11.2 microdeletions are recurrent microdeletions with an overall prevalence of 0.03%. In patients with segmentation defects of the vertebra (SDV), a burden of this microdeletion was observed with TBX6 as a candidate gene for SDV. In a published cohort of patients with congenital scoliosis (CS), TBX6 haploinsufficiency was compound heterozygous with a common haplotype. Besides, a single three-generation family with spondylocostal dysostosis (SCD) was reported with a heterozygous stop-loss of TBX6. These observations questioned both on the inheritance mode and on the variable expressivity associated with TBX6-associated SDV. Based on a national recruitment of 56 patients with SDV, we describe four patients with variable SDV ranging from CS to SCD associated with biallelic variations of TBX6. Two patients with CS were carrying a proximal 16p11.2 microdeletion associated with the previously reported haplotype. One patient with extensive SDV was carrying a proximal 16p11.2 microdeletion associated with a TBX6 rare missense change. One patient with a clinical diagnosis of SCD was compound heterozygous for two TBX6 rare missense changes. The three rare variants were affecting the chromatin-binding domain. Our data illustrate the variable expressivity of recessive TBX6 ranging from CS to SCD.

Compound Heterozygosity for Null Mutations and a Common Hypomorphic Risk Haplotype in TBX6 Causes Congenital Scoliosis

Congenital scoliosis (CS) occurs as a result of vertebral malformations and has an incidence of 0.5-1/1,000 births. Recently, TBX6 on chromosome 16p11.2 was reported as a disease gene for CS; about 10% of Chinese CS patients were compound heterozygotes for rare null mutations and a common haplotype defined by three SNPs in TBX6. All patients had hemivertebrae. We recruited 94 Japanese CS patients, investigated the TBX6 locus for both mutations and the risk haplotype, examined transcriptional activities of mutant TBX6 in vitro, and evaluated clinical and radiographic features. We identified TBX6 null mutations in nine patients, including a missense mutation that had a loss of function in vitro. All had the risk haplotype in the opposite allele. One of the mutations showed dominant negative effect. Although all Chinese patients had one or more hemivertebrae, two Japanese patients did not have hemivertebra. The compound heterozygosity of null mutations and the common risk haplotype in TBX6 also causes CS in Japanese patients with similar incidence. Hemivertebra was not a specific type of spinal malformation in TBX6-associated CS (TACS). A heterozygous TBX6 loss-of-function mutation has been reported in a family with autosomal-dominant spondylocostal dysostosis, but it may represent a spectrum of the same disease with TACS.

Fetus with Casamassima-Morton-Nance Syndrome and Limb-Body Wall Defect: Presentation of a Novel Association and Review of the Phenotype

In 1981, Casamassima and colleagues described an autosomal recessive syndrome of spondylocostal dysostosis associated with anal and urogenital anomalies. Here, I describe 1 new fetus who presented with limb-body wall defect as a novel association, compile 7 patients, and review the clinical phenotype of Casamassima-Morton-Nance syndrome. This appears to be the 1st Casamassima-Morton-Nance syndrome fetus with this complex malformation. In light of this manifestation, a detailed comparative phenotypic analysis of published patients revealed a heterogeneous syndrome with significant clinical variability. Accordingly, it is proposed that Casamassima-Morton-Nance syndrome should be considered in those patients with the combination of a short and asymmetric thorax with rib and vertebral anomalies and scoliosis (spondylocostal-like pattern), anal atresia, absent external genitalia, renal and urethral abnormalities (caudal dysgenesis complex), craniofacial dysmorphic features (mainly flat nose with anteverted nares, low-set/abnormal ears, and short neck), hydrops, oligohydramnios, and a poor clinical outcome.

Spondylocostal dysostosis (Jarcho-Levine syndrome) associated with occult spinal dysraphism: Report of two cases

Spondylocostal dysostosis, also known as Jarcho-Levine syndrome, is a rare disorder characterized by multiple vertebral and rib anomalies at birth. The association of occult spinal dysraphic lesions with this entity is rare. Two patients with spondylocostal dysostosis and occult spinal dysraphic lesions, one with type I split cord malformation and another with spinal dermal sinus are being reported. A 7-month-old female child who was operated at birth for imperforate anus was noted to have a dimple at the low back with altered skin color around the dimple. Examination revealed the right lower extremity was slightly thinner than the left. Plain radiographs showed features of spondylocostal dysostosis with scoliosis. Magnetic resonance imaging (MRI) showed a type I split cord malformation at the lumbosacral junction with low-lying conus and terminal syringomyelia. Patient underwent excision of the bony spur uneventfully. A 14-month-old male child was noted to have a small swelling in the low back along with deformity of the right lower chest since birth. Plain radiographs revealed features of spondylocostal dysostosis. MRI showed a spinal dermal sinus at the lumbosacral junction with a low-lying conus. The patient underwent excision of the spinal dermal sinus and untethering of the cord uneventfully. Although rare, spondylocostal dysostosis can be associated with occult spinal dysraphic lesions like type I split cord malformations or spinal dermal sinus. Physicians should be aware about the possibility of children with spondylocostal dysostosis harboring occult spinal dysraphic lesions so that these patients receive appropriate treatment.

Spondylocostal dysostosis with lipomyelomeningocele: Case report and review of the literature

Spondylocostal dysostosis (SCDO) is rare anomaly caused due to flawed embryological development of the axial skeleton during preliminary stages of gravidity, characterized by malformed vertebral column and ribs, abridged thorax and kyphoscoliosis. This entity was also reported as a "Jarcho-Levin syndrome" eponym by erstwhile authors, before the introduction of genetic based classification. A literature review showed only three cases of this clinical entity with lipomyelomeningocele. We report the fourth case report of an infant with SCDO with lipomyelomeningocele. His chest X-ray displayed absent left side 6(th)-8(th) ribs with peculiar fan like configuration, making the heart vulnerable to any direct injury. Special care has to be taken for such patients who need surgical procedure in the prone position.

Spondylocostal dysostosis with tetralogy of Fallot and herniation of the spleen through the diaphragm

Spondylocostal dysostosis (SCD) is a very rare syndrome characterized by vertebral malformation and rib deformity. Some of the patients with SCD have other birth defects in the central nervous system, the genitourinary tract, diaphragm or heart and so forth. There have been reported SCD with complex congenital heart disease, such as pulmonary atresia, double outlet right ventricle, and d-transposition of great arteries. However, there have been no reported SCD patients with confirmed tetralogy of Fallot (TOF). Here, a patient with SCD having a very rare combination of rib defects on the right side and left-sided scoliosis, tetralogy of Fallot, and diaphragmatic spleen herniation, which had not been reported before, was described.

A rare case of fetal spondylocostal dysostosis - prenatal diagnosis and perinatal care in a patient with multiple large leiomyomas

The spondylocostal dysostosis (SCD) is one of the two major clinico-radiological subtypes of the Jarcho-Levin syndrome (JLS). The JLS is a rare heterogeneous entity characterized by facial dysmorphism, short-neck, short-trunk, normal sizes limbs, with multiple vertebral anomalies at all levels of the vertebral column and costal defects. The JLS has been classified into 2 major clinical phenotypes, based on the extent and distribution of skeletal anomalies, the pattern of inheritance and the prognosis. We report the case of a non-consanguineous 35-year-old female patient, with a history of multiple large leiomyomas gravida 1, para 1. A three-dimensional ultrasound at 18 weeks of gestation revealed: thoracic and lumbar hemivertebrae with abnormal alignment of the vertebral bodies and kypho-scoliosis, also the absence of two right ribs and abnormal shaped ribs. The biometric measurement was appropriate for gestational age and no other malformations were found. Although there was no previous history, based on the three-dimensional ultrasound findings a mild subtype of JLS was suspected. At term, the patient gave birth, by Cesarean section, to a male fetus, with a weight of 2700g, a length of 50cm and a calculated Apgar score of 9. The postpartum examination of the fetus confirmed the diagnose of SCD. The evolution of the newborn was good - he had no respiratory difficulty; he will benefit from an experimental surgery involving expandable titanium ribs. Our case illustrates the importance of an accurate ultrasound examination, which can be hindered by multiple large leyomiomas, in order to diagnose and to differentiate the two subtypes of JLS. The SCD can have a favorable evolution with the appropriate perinatal and postpartum care.

Jarcho-Levin syndrome with diastematomyelia: A case report and review of literature

Jarcho–Levin syndrome (JLS) is a type of segmental costovertebral malformation. It is a congenital disorder characterized by a variety of vertebral and costal anomalies. Only four cases of Jarcho–Levin syndrome with diastematomyelia have been reported in the literature. We report the fifth case of Jarcho–Levin syndrome with diastematomyelia and review the literature. A one-and-half-year-old male child born of full-term normal delivery was brought with complaints of progressively increasing weakness in lower limbs with inability to stand since 1 month. Radiological examination revealed irregular fusion of ribs, spina bifida, and diastematomyelia at L2–L3 vertebral level. The patient underwent L1 to L3 laminectomy. A large bony spur was identified and excised with microrongeurs. Spondylocostal dysplasia may be associated with diastematomyelia or other surgically correctable occult intraspinal anomalies which may be diagnosed in early asymptomatic stage by magnetic resonance image screening of spine.