MECP2 Duplication Syndrome, also known as X-linked intellectual developmental disorder Lubs type (MRXSL; MIM: 300260), is a neurodevelopmental disorder caused by copy number gains spanning MECP2. Despite varying genomic rearrangement structures, including duplications and triplications, and a wide range of duplication sizes, no clear correlation exists between DNA rearrangement and clinical features. We had previously demonstrated that up to 38

Wiedemann-Steiner syndrome (WDSTS) is an autosomal dominant disorder that is caused by mutations in the KMT2A gene. This case reports a two-year-old male’s diagnosis of WDSTS via a heterozygous variant of uncertain significance (VUS) (c.11735G>A(p.Cys3912Tyr). The patient's phenotypic presentation was remarkable for hypertrichosis, intellectual disability, intermittent aggressive behavior, developmental delay, failure to thrive, low weight, and the distinct facial features of long eyelashes, telecanthus, corrected strabismus, down-slanting palpebral fissures, and a wide nasal bridge with a broad tip. The importance of this case report stands on the principle of genetic evaluation in patients with ambiguous clinical presentations. In the future, molecular analysis of VUS with pathogenic clinical features can lead to targeted medical management and counseling.

OBJECTIVES/GOALS: Diagnostic odyssey is the time it can take to a patient for receiving a diagnosis. Diagnostic process in rare diseases can be complex due to the heterogeneity of symptoms and lack of access to care. We aim to evaluate the association between diagnostic odyssey, perceived stress, and access to care, in parents of Puerto Rican patients with a rare disease. METHODS/STUDY POPULATION: We propose a cross-sectional study in parents of 100 children who received an uninformative whole exome sequencing (WES) report during a scheduled appointment with their geneticist. Discussion of WES results during clinical session, followed by a Perceived Stress Scale (PSS-10) and semi-structured interview to explore the experience of access to care during the diagnostic process will be arranged. Observation and interviews will be recorded. Data analysis and descriptive statistics will be calculated using STATA. Statistical associations (OR) will be estimated using generalized linear models at a 5% significance level. RESULTS/ANTICIPATED RESULTS: We expect to find high perceived stress in parents of Puerto Rican pediatric individuals having rare diseases, especially among single mothers. We will be able to identify limited access to care in Puerto Rico, especially in the testing pre-authorization process and long waits for geneticist appointments. Demand for advanced diagnostics is above the number of medical geneticists available in Puerto Rico, which triggers delayed diagnosis, management, and counseling. Therefore, these could affect the health disparities in our population with rare diseases. DISCUSSION/SIGNIFICANCE: This descriptive study will evaluate perceived stress in parents of pediatric patients living a diagnostic odyssey in Puerto Rico. No study has described perceived stress and access to care in this Hispanic population with undiagnosed conditions. Findings will contribute to a deep understanding of diagnostic process and limited access to care.

Human vertebral malformations (VMs) have an estimated incidence of 1/2000 and are associated with significant health problems including congenital scoliosis (CS) and recurrent organ system malformation syndromes such as VACTERL (vertebral anomalies; anal abnormalities; cardiac abnormalities; tracheo-esophageal fistula; renal anomalies; limb anomalies). The genetic cause for the vast majority of VMs are unknown. In a CS/VM patient cohort, three COL11A2 variants (R130W, R1407L and R1413H) were identified in two patients with cervical VM. A third patient with a T9 hemivertebra and the R130W variant was identified from a separate study. These substitutions are predicted to be damaging to protein function, and R130 and R1407 residues are conserved in zebrafish Col11a2. To determine the role for COL11A2 in vertebral development, CRISPR/Cas9 was used to create a nonsense mutation (col11a2L642*) as well as a full gene locus deletion (col11a2del) in zebrafish. Both col11a2L642*/L642* and col11a2del/del mutant zebrafish exhibit vertebral fusions in the caudal spine, which form due to mineralization across intervertebral segments. To determine the functional consequence of VM-associated variants, we assayed their ability to suppress col11a2del VM phenotypes following transgenic expression within the developing spine. While wildtype col11a2 expression suppresses fusions in col11a2del/+ and col11a2del/del backgrounds, patient missense variant-bearing col11a2 failed to rescue the loss-of-function phenotype in these animals. These results highlight an essential role for COL11A2 in vertebral development and support a pathogenic role for two missense variants in CS.

BACKGROUND:Spondylothoracic dysostosis (STD), also known as Jarcho-Levin syndrome (JLS), is a rare autosomal recessive disorder affecting the formation of the spine, characterized by a complete bilateral fusion of the ribs at the costovertebral junction, producing a "crablike" appearance of the thorax. Despite being declared a core indication for a V-osteotomy vertical expandable prosthetic titanium rib (VEPTR) expansion thoracoplasty of the posterior thorax, the natural history of STD in untreated subjects remains poorly documented. In this study, we report radiographic and pulmonary function findings and Patient-Reported Outcomes Measurement Information System (PROMIS) and 24-Item Early Onset Scoliosis Questionnaire (EOSQ-24) scores for untreated adult subjects with STD to gain insights into the natural history. METHODS:We identified 11 skeletally mature, untreated subjects with STD. Findings on medical evaluation, demographics, radiographic parameters, pulmonary function, genetic testing results, PROMIS measures, and EOSQ-24 scores were assessed. RESULTS:Five male and 6 female subjects (mean age, 32.3 years [range, 15 to 70 years]) with a confirmed STD diagnosis based on radiographs and genetic testing were evaluated. Mean body mass index (BMI) was 24.4 kg/m 2 (range, 18 to 38.9 kg/m 2 ), and mean thoracic height was 16 cm (range, 12 to 17 cm). Pulmonary function tests (PFTs) showed a mean forced vital capacity (FVC) of 22% of predicted, mean forced expiratory volume in 1 second (FEV1) of 24% of predicted, and FEV1/FVC ratio of 107% of predicted. The mean PROMIS dyspnea score was 40 ± 8 points (range, 27.7 to 52.1 points). The mean total EOSQ-24 score was 77.3 ± 18 points (range, 43.9 to 93.2 points). CONCLUSIONS:Our study characterizes the natural history of STD in untreated subjects. We confirmed the expected restrictive pattern in pulmonary function, but interestingly, our subjects exhibited better EOSQ scores compared with those reported in neuromuscular populations. PFT results and thoracic height did not correspond to PROMIS and EOSQ scores, questioning the use of those parameters as a surgical indication. We therefore suggest that the STD diagnosis as an absolute indication for VEPTR expansion thoracoplasty surgery be reconsidered. LEVEL OF EVIDENCE:Therapeutic Level IV . See Instructions for Authors for a complete description of levels of evidence.

BACKGROUND Osteogenesis imperfecta is a skeletal disease with a range of phenotypes, depending on the genetic mutation. Individuals with osteogenesis imperfecta type I often have mutations in COL1A genes. This disease can be associated with chest wall deformities such as pectus excavatum, but the number of patients with this presentation is limited, and genetic variants associated with this phenotype have not been reported. CASE REPORT We studied the Skeletal Disorders Genetic Panel of 2 siblings with osteogenesis imperfecta type I and severe pectus excavatum requiring surgical correction. Both had severe respiratory symptoms secondary to the chest wall deformity, and the male patient had evidence of mitral valve insufficiency on an echocardiogram. Results of the genetic panel were remarkable for a homozygous copy number gain in exons 2 to 51 in gene COL1A1. Additionally, both had a heterozygous pathogenic variant in exon 7 of gene COL27A1 (replacement of a glycine with arginine in codon 697 of the protein). CONCLUSIONS Gene COL27A1 plays a role during the calcification of cartilage to bone and is associated with Steel syndrome, a skeletal disorder mainly found in the Puerto Rican population. Heterozygous carriers of the p.Gly697Arg variant in COL27A1 have not been described to have a phenotype with chest wall deformities. Additionally, a genotype-phenotype relationship regarding pectus excavatum in patients with osteogenesis imperfecta has not been described, suggesting that having COL1A gene mutations and simultaneous haploinsufficiency of COL27A1 can result in a phenotype of osteogenesis imperfecta with pectus excavatum and predispose these patients to additional phenotypic features.

Stickler Syndrome is a rare clinically and genetically heterozygous connective tissue disorder with variable clinical presentation including serious vision (eg, myopia, cataract, and retinal detachment), hearing loss (eg, sensorineural, mixed and/or conductive), craniofacial abnormalities (midface underdevelopment and cleft palate) and joint problems (eg, precocious arthritis, spondyloepiphyseal dysplasia). Stickler syndrome is associated with pathogenic variants in the COL2A1, COL11A1, COL11A2, COL9A1, COL9A2 and COL9A3 genes are present. This syndrome is mainly inherited as an autosomal dominant pathology. We are presenting the case of a 15-year-old female who was referred to genetics by cardiology due to hypoglycemia, tachycardia and to rule out Marfan syndrome due to Marfanoid habitus. Upon physical examination there was evidence of joint hyperlaxity and decreased muscle tone. She also presented mild thoracolumbar dextroscoliosis of 25 degrees in curvature documented by spine X-rays. A connective tissue disorder gene panel was requested. The results indicate that the patient is heterozygous for variants in three genes: COL11A1, COL9A2 and NEPRO. The COL11A1 gene is responsible for providing the blueprint to synthesize a component of type XI collagen, which is commonly located in cartilage. Type XI collagen can also be found in the inner ear, the vitreous and in the nucleus pulposus. A sequence variant c.4718C>T in the COL11A1 gene was identified in this patient. This change is expected to cause an amino acid substitution p.Ser1573Leu, which has not been reported in the literature. Pathogenic variants in COL11A1 have been associated with autosomal dominant Stickler syndrome type II, autosomal dominant Marshall syndrome, autosomal dominant deafness 37 as well as autosomal recessive fibrochondrogenesis 1. COL9A2 gene provides the blueprint for synthesizing a part of a large molecule called type IX collagen, which is more flexible than other types of collagen. A sequence variant designated as c.1553G>T was documented in this gene and is expected to result in an amino acid substitution designated as p.Arg518Leu. Pathogenic variants in COL9A2 have been linked with autosomal recessive Stickler syndrome type V and autosomal multiple epiphyseal dysplasia 2. This variant has not been reported in the literature. The NERPRO (Nucleolus and neural progenitor protein) gene could be involved in cortex development as part of the Notch signaling pathway and it may also be involved in preimplantation embryo development. A NEPRO gene sequence variant designated as c.871G>A was documented as well. This sequence variant is expected to result in an amino acid substitution p.Val291Met. This variant has not been reported in the literature. Fifteen years old female with genetic variants on COL11A1, COL9A2 and NEPRO genes. The patient presents scoliosis, myopia, and amblyopia, micrognathia, hyperlaxed joints and hypotonia. The COL11A1 and the COL9A2 genes has been associated with autosomal dominant and autosomal recessive Stickler syndrome phenotypes respectively. Stickler syndrome is a connective tissue disorder that can include ocular findings of myopia, cataract, and retinal detachment; hearing loss that is both conductive and sensorineural; midfacial underdevelopment and cleft palate (either alone or as part of the Robin sequence). The COL11A1 variant has not been reported in the medical literature associate to the disease however predictive algorithms suggest the possibility of a deleterious effect on the protein. The patient also has a genetic variant on the COL9A2 gene that has not been associate to the disease but haploinsufficiency mechanisms may also be playing a role in this patient phenotype.

OBJECTIVES/GOALS: Assess the diagnostic yield and test utilization of WES in patients having complex traits. We aim to evaluate the use of the first genetic approach for the identification of primary variants that contribute to neurogenetic disease etiology and influence onset and progression in Puerto Ricans. METHODS/STUDY POPULATION: Prospective cohort of 45 Puerto Rican probands (19 months - 36 years old) with complex neurogenetic traits that underwent WES (2019 - 2021). WES was performed, including copy number variant analysis and mitochondrial genome sequencing. We evaluated several factors possibly influencing the rate of WES diagnosis including early age, consanguinity, and family history of neurogenetic diseases. In addition, we only evaluated probands rather than dyads/trios and the clinical phenotypes. Descriptive analysis was performed, including a catalog of all variants reported. Multivariate analysis was performed to estimate the statistical association between variants and phenotypes reported and adjusting for potential confounders (age, sex, family history, income, health insurance and zip code). RESULTS/ANTICIPATED RESULTS: Auspiciously, positive pathogenic findings altered the clinical management in 29% of the probands in this study. A likely genetic diagnosis was achieved in 53% of the probands including pathogenic, likely pathogenic and variants of uncertain significance. Intronic variants, copy number variants detection and mitochondrial genome was included in WES methodology. Despite these facts, a 47% of the reported WES were negative, which deserve re-analysis potentially genotype based. Multivariate analysis is expected to adjust for potential confounders to establish a genotype-phenotype correlations in neurogenetic complex traits in this Puerto Rican admixed population. DISCUSSION/SIGNIFICANCE: Clinical WES offers an alternative approach for identification of variants in patients with complex traits. WES is also applicable in genetically heterogeneous individuals when specific genetic tests are not available or unsuccessful. Variants reported contribute to understand complex neurogenetic disease in underrepresented Puerto Ricans.

We are presenting the case of a 6-year-old male patient with progeroid phenotype and severe developmental delay referred to Genetic clinic. Given the complex phenotype an extensive metabolic and genetic evaluation was performed including a whole exome sequencing analysis that showed genetic variants in TTR, RELN, MYH6, PHIP, and SYNE2 genes. Patients' mother and brother were analyzed for the genetic variants in MYH6, PHIP and RELN. Both had same variants on PHIP and RELN as our patient, with no apparent phenotypical consequences. Physical examination was remarkable for dysmorphism including plagiocephaly, low set and abnormally shaped ears, up slanted palpebral fissures, hypoplastic alae nasi, and a head circumference two standard deviations below the 3rd percentile (microcephaly). Other characteristics include wrinkled skin, a broad forehead, sparse eyelashes in lower eyelid, short palpebral fissures, upturned nares, thick lips, right occipital plagiocephaly, overfolded helix and prominent anti-helix, protuberant chest, scaphoid abdomen, digitalized thumbs, and kyphosis due to low muscle tone. The patient presented abnormal EEG with evidence of epileptic discharges. A temporal bone CT showed plagiocephaly with flattening of the right occipital bone. Brain MRI showed callosal agenesis with bilateral colpocephaly with temporal horn dilatation, parahippocampal atrophy, lissencephaly and midbrain hypoplasia. The combination of de novo gene variants mentioned above has never been reported nor correlated as the result of haploinsufficiency mechanisms. Thus, we propose haploinsufficiency and loss of heterozygosity as etiological reasons for this patient phenotype. Further proteomic studies are needed to allocate the extense of genetic influence within the clinical manifestations.

ABSTRACT IMPACT: Alterations in mitochondrial metabolism affect any tissue, especially those with the highest demand for energy. As the symptoms and clinical manifestations are heterogenous, disease diagnosis is challenging. The implementation of genetic-first approach in the diagnosis of mitochondrial diseases will expedite confirmation, treatment, management, and counseling of affected Puerto Rican individuals. OBJECTIVES/GOALS: Mitochondrial diseases are rare, and diagnosis is complex due to the heterogeneity of clinical manifestations. We aim to develop and implement a testing algorithm using a genetics-first approach, facilitating the identification of variants that contribute to mitochondrial disease’s etiology and influence onset and progression in Puerto Ricans. METHODS/STUDY POPULATION: This is a cross-sectional study for characterizing clinical laboratory results from profiles used to evaluate metabolic diseases in individuals with suspected mitochondrial disorders from 2018 to 2021. A subset of 25 individuals from biochemical profile will be recruited to analyze their medical and family history, metabolic biomarkers in blood and urine, hearing test, imaging and chromosomal microarray. The implementation of a genetic testing algorithm using whole exome and mitochondrial DNA sequencing will be performed in a subset of 11 randomized individuals. Descriptive analysis will be reported, including a catalog of all variants. Multivariate analysis will be performed to estimate the statistical association between variants and phenotypes reported and adjusting for potential confounders. RESULTS/ANTICIPATED RESULTS: The biochemical profile of pediatric Puerto Rican individuals suspected of having mitochondrial diseases will be altered and can be used to differentiate among other metabolic causes. We expect to find altered levels of lactate, pyruvate and carnitines in serum, as well as altered organic acids in urine. The implementation of a testing algorithm using both, mitochondrial DNA and whole exome sequencing as first approach will be enabling the identification of disease-causing variants, thus enhancing and confirming the diagnosis of mitochondrial disease in Puerto Ricans. We will be able to identify rare/novel variants specific to our Hispanic population, for both nuclear and mitochondrial DNA. DISCUSSION/SIGNIFICANCE OF FINDINGS: This study will help to characterize the metabolic profile of pediatric Puerto Ricans. No previous study has been reported that describes testing algorithms for genetic diagnosis of mitochondrial disease in our population. Variants found will contribute to a deep understanding of the genetic contribution to phenotypes and disease susceptibility.

Previously we reported the identification of a homozygous COL27A1 (c.2089G>C; p.Gly697Arg) missense variant and proposed it as a founder allele in Puerto Rico segregating with Steel syndrome (STLS, MIM #615155); a rare osteochondrodysplasia characterized by short stature, congenital bilateral hip dysplasia, carpal coalitions, and scoliosis. We now report segregation of this variant in five probands from the initial clinical report defining the syndrome and an additional family of Puerto Rican descent with multiple affected adult individuals. We modeled the orthologous variant in murine Col27a1 and found it recapitulates some of the major Steel syndrome associated skeletal features including reduced body length, scoliosis, and a more rounded skull shape. Characterization of the in vivo murine model shows abnormal collagen deposition in the extracellular matrix and disorganization of the proliferative zone of the growth plate. We report additional COL27A1 pathogenic variant alleles identified in unrelated consanguineous Turkish kindreds suggesting Clan Genomics and identity-by-descent homozygosity contributing to disease in this population. The hypothesis that carrier states for this autosomal recessive osteochondrodysplasia may contribute to common complex traits is further explored in a large clinical population cohort. Our findings augment our understanding of COL27A1 biology and its role in skeletal development; and expand the functional allelic architecture in this gene underlying both rare and common disease phenotypes.

Epigenetic mechanisms, genetic factors, and environment influence the diversity of phenotypes developed in various diseases. Duplications in several chromosomes are well characterized in the scientific literature, but partial duplications, in some cases, present with milder forms of a disease and are yet to be understood. Fortunately, the identification of genetic diseases has now become more feasible due to several cytogenetic techniques such as microarray analysis and karyotyping. With these tools, together with other laboratory results and clinical examination, we are able to report the first case in the medical literature of double partial trisomy of chromosome 9q34 and 16p13.

Hermansky-Pudlak syndrome (HPS) is a rare autosomal recessive genetic disorder characterized by oculocutaneous albinism and a bleeding diathesis due to platelet dysfunction. More than 50% of cases worldwide are diagnosed on the Caribbean island of Puerto Rico. Genetic testing plays a growing role in diagnosis; however, not all patients with HPS have identified genetic mutations. In Puerto Rico, patients with HPS are often identified shortly after birth by their albinism, although the degree of hypopigmentation is highly variable. Ten subtypes have been described. Patients with HPS-1, HPS-2, and HPS-4 tend to develop pulmonary fibrosis in Puerto Rico; 100% of patients with HPS-1 develop HPS-PF. HPS-PF and idiopathic pulmonary fibrosis are considered similar entities (albeit with distinct causes) because both can show similar histological disease patterns. However, in contrast to idiopathic pulmonary fibrosis, HPS-PF manifests much earlier, often at 30-40 years of age. The progression of HPS-PF is characterized by the development of dyspnea and increasingly debilitating hypoxemia. No therapeutic interventions are currently approved by the U.S. Food and Drug Administration for the treatment of HPS and HPS-PF. However, the approval of two new antifibrotic drugs, pirfenidone and nintedanib, has prompted new interest in identifying drugs capable of reversing or halting the progression of HPS-PF. Thus, lung transplantation remains the only potentially life-prolonging treatment. At present, two clinical trials are recruiting patients with HPS-PF to identify biomarkers for disease progression. Advances in the diagnosis and management of these patients will require the establishment of multidisciplinary centers of excellence staffed by experts in this disease.

Neonatal nonketotic hyperglycinemia is an autosomal recessive inborn disorder of glycine metabolism in which large quantities of glycine accumulate in all body tissues. It is characterized by a progressive lethargy, hypotonia, myoclonic jerks, and early death secondary to respiratory problems. As a result of early diagnosis and treatment protocols, more patients survive the critical neonatal period with profound mental retardation, delayed developmental milestones, seizures, and spasticity. There are no reports about the orthopaedic manifestations of neonatal nonketotic hyperglycinemia. The purpose of this study is to evaluate the musculoskeletal findings of neonatal nonketotic hyperglycinemia.

In 1938, Saul Jarcho and Paul Levin from Johns Hopkins Hospital reported cases of thoracic insufficiency due to vertebral and rib anomalies. Nearly 30 years later, in 1966, Norman Lavy and associates from Indiana University reported a similar syndrome in a family from Puerto Rico. Lavy's description was followed by a report by John E. Moseley from New York City, where the name spondylothoracic dysplasia (dysostosis) was first used. For more than half a century, there has been confusion regarding the distinction between these two phenotypically similar syndromes that cause thoracic insufficiency. Spondylocostal dysostosis (SCD), or Jarcho-Levin syndrome, causes mild to moderate respiratory insufficiency, is panethnic and has been linked to genes such as DLL3, which is known to be associated with the Notch pathway. In contrast, spondylothoracic dysostosis (STD), or Lavy-Moseley syndrome, results in more severe respiratory compromise, is largely linked to Puerto Rican cohorts and is thought to be associated to the MESP2 gene, also a Notch pathway gene. Long-term studies of Puerto Rican cohorts with STD contradicts the previously held belief that individuals affected with STD have markedly diminished life expectancy with as many as 25% surviving into later childhood and adult life.

Background A syndrome of children with short stature, bilateral hip dislocations, radial head dislocations, carpal coalitions, scoliosis, and cavus feet in Puerto Rican children, was reported by Steel et al in 1993. The syndrome was described as a unique entity with dismal results after conventional treatment of dislocated hips. The purpose of this study is to reevaluate this patient population with a longer follow-up and delineate the clinical and radiologic features, treatment outcomes, and the genetic characteristics. Methods This is a retrospective cohort study of 32 patients in whom we evaluated the clinical, imaging data, and genetic characteristics. We compare the findings and quality of life in patients with this syndrome who have had attempts at reduction of the hips versus those who did not have the treatment. Results Congenital hip dislocations were present in 100% of the patients. There was no attempt at reduction in 39% (25/64) of the hips. In the remaining 61% (39/64), the hips were treated with a variety of modalities fraught with complications. Of those treated, 85% (33/39) remain dislocated, the rest of the hips continue subluxated with acetabular dysplasia and pain. The group of hips that were not treated reported fewer complaints and limitation in daily activities compared with the hips that had attempts at reduction. Conclusions Steel syndrome is a distinct clinical entity characterized by short stature, bilateral hip and radial head dislocation, carpal coalition, scoliosis, cavus feet, and characteristic facial features with dismal results for attempts at reduction of the hips. Level of Evidence Prognostic Study Level II.

Existing nomenclature systems for describing and reporting congenital segmentation defects of the vertebrae (SDV) are confusing, inconsistently applied, and lack molecular genetic advances. Our aim was to develop and assess a new classification system for SDV. A multidisciplinary group of the International Consortium for Vertebral Anomalies and Scoliosis (ICVAS) developed a new classification system for SDV, and 5 members group (Group 1) independently classified 10 previously unseen cases using this system. Inter-observer reliability was assessed using kappa, which compares observed agreement with that expected by chance. Seven independent general radiologists unaffiliated with the ICVAS (Group 2) classified the same 10 cases (total, 70 scores) before and after the ICVAS system was explained. We demonstrated the following: Inter-observer reliability for Group 1 yielded a kappa value of 0.21 (95% confidence intervals (CI) 0.052, 0.366, P = 0.0046); A consensus diagnosis was established for the 10 cases. For Group 2, before the ICVAS system was explained, 1 of 70 scores (1.4%) agreed with the Group 1 consensus diagnoses; Group 2 offered 12 different diagnoses, but 38 of 70 (54.3%) responses were "Don't Know." After the ICVAS system was explained, 47 of 70 responses (67.1%; 95% CI 55.5, 77.0) agreed with the Group 1 consensus, an improvement of 65.7% (95% CI 52.5, 75.6, P < 0.00005), with no "Don't Know" responses. Group 2 average reporting times, before and after explanation of the ICVAS system, were 148 and 48 min, respectively. We conclude that the ICVAS radiological classification system was found to be reliable and applicable for 10 SDV phenotypes.

The study aimed to develop and assess a new classification system for Segmentation Defects of the Vertebrae (SDV), a frequent cause of congenital scoliosis. Existing nomenclature for the wide range of SDV phenotypes is inadequate and confusing eg ‘Jarcho-Levin syndrome’. A multidisciplinary group of the International Consortium for Vertebral Anomalies and Scoliosis (ICVAS) met to formulate a new classification system, based primarily on radiology. SDV are identified by number affected, contiguity, and spinal region(s). The size, shape and symmetry of the thoracic cage, and rib number, symmetry and fusion are included, and familiar vertebral morphology terms retained, together with accepted syndrome names. The terms spondylocostal and spondylothoracic dysostosis apply only to phenotypes typified by the monogenic disorders due to mutated DLL3, MESP2, LNFG and HES7 genes. Five ICVAS members (Group 1) then independently assessed 10 new cases, inter-observer reliability assessed using kappa. Seven independent radiologists (Group 2) then assessed the same cases before and after introduction to the new system. Inter-observer reliability for Group 1 yielded a kappa value of 0.21 (95% confidence intervals (CI) 0.052, 0.366, p=0.0046). For Group 2, before introduction to the new system, 1/70 responses (1.4%) agreed with the Group 1 consensus,12 different diagnoses were offered, and 38/70 (54.3%) responses were ‘Unknown’. After introduction to the new system 47/70 responses (67.1%; 95% CI 55.5, 77.0) agreed with Group 1 consensus, a 65.7% improvement (95% CI 52.5, 75.6, p The new system was found to be reliable and acceptable. Ethics approval: None Interest Statement: None