Insights into Craniofacial Development and Anomalies: Exploring Fgf Signaling in Zebrafish Models.

PURPOSE OF REVIEW: To illustrate the value of using zebrafish to understand the role of the Fgf signaling pathway during craniofacial skeletal development under normal and pathological conditions. RECENT FINDINGS: Recent data obtained from studies on zebrafish have demonstrated the genetic redundancy of Fgf signaling pathway and have identified new molecular partners of this signaling during the early stages of craniofacial skeletal development. Studies on zebrafish models demonstrate the involvement of the Fgf signaling pathway at every stage of craniofacial development. They particularly emphasize the central role of Fgf signaling pathway during the early stages of the development, which significantly impacts the formation of the various structures making up the craniofacial skeleton. This partly explains the craniofacial abnormalities observed in disorders associated with FGF signaling. Future research efforts should focus on investigating zebrafish Fgf signaling during more advanced stages, notably by establishing zebrafish models expressing mutations responsible for diseases such as craniosynostoses.

Relevance of Extending FGFR3 Gene Analysis in Osteochondrodysplasia to Non-Coding Sequences: A Case Report.

Skeletal dysplasia, also called osteochondrodysplasia, is a category of disorders affecting bone development and children's growth. Up to 552 genes, including fibroblast growth factor receptor 3 (FGFR3), have been implicated by pathogenic variations in its genesis. Frequently identified causal mutations in osteochondrodysplasia arise in the coding sequences of the FGFR3 gene: c.1138G>A and c.1138G>C in achondroplasia and c.1620C>A and c.1620C>G in hypochondroplasia. However, in some cases, the diagnostic investigations undertaken thus far have failed to identify the causal anomaly, which strengthens the relevance of the diagnostic strategies being further refined. We observed a Caucasian adult with clinical and radiographic features of achondroplasia, with no common pathogenic variant. Exome sequencing detected an FGFR3(NM_000142.4):c.1075+95C>G heterozygous intronic variation. In vitro studies showed that this variant results in the aberrant exonization of a 90-nucleotide 5' segment of intron 8, resulting in the substitution of the alanine (Ala359) for a glycine (Gly) and the in-frame insertion of 30 amino acids. This change may alter FGFR3's function. Our report provides the first clinical description of an adult carrying this variant, which completes the phenotype description previously provided in children and confirms the recurrence, the autosomal-dominant pathogenicity, and the diagnostic relevance of this FGFR3 intronic variant. We support its inclusion in routinely used diagnostic tests for osteochondrodysplasia. This may increase the detection rate of causal variants and therefore could have a positive impact on patient management. Finally, FGFR3 alteration via non-coding sequence exonization should be considered a recurrent disease mechanism to be taken into account for new drug design and clinical trial strategies.

Primary Staged Bilateral Total Hip Arthroplasty in a Patient With Short Stature and Hartofilakidis Type I Developmental Dysplasia of the Hip.

Syndromes associated with osteochondrodysplasia, short stature, and DDH are rarely reported in the literature. Total hip arthroplasty (THA) in such cases is a complex procedure with a high rate of complications and difficulties. In this case report, we describe the staged bilateral complex primary THA of a patient with the rare occurrence of a syndrome involving osteochondrodysplasia and DDH, highlighting the surgical challenges and importance of the right prosthesis selection.

Osteochondrodysplasia and the c.1024G>T variant of TRPV4 gene in Scottish Fold cats: genetic and radiographic evaluation.

OBJECTIVES: The objectives of this study were to investigate the c.1024G>T SNP in the TRPV4 gene in Scottish Straight and Fold cats, and to evaluate the pattern of skeletal phenotype and the evolution of radiological signs of Scottish Fold osteochondrodysplasia (SFOCD) over time in heterozygous subjects. METHODS: DNA was obtained from blood samples of 17 cats (Scottish Fold: n = 12; Scottish Straight: n = 5) and subsequently genotyped by sequencing in a 249 bp region of the TRPV4 gene (exon 6), including the known c.1024G>T causative mutation for osteochondrodysplasia. Orthopaedic and radiographic analyses were performed on animals carrying the mutant allele. RESULTS: Genotyping by sequencing confirmed that all and only the Scottish Fold cats carried the mutant allele in a heterozygous asset. Furthermore, two other exon variants, already described in the literature as silent variants, were found in some of the sampled cats. Comparative orthogonal radiographic views of the shoulder, elbow, carpus, hip, stifle and tarsus were obtained. A mediolateral projection of the thoracic and lumbar column was also performed. Three out of four cats were clinically and radiographically examined again 1.5 years later. CONCLUSIONS AND RELEVANCE: Although the presence of the mutant allele in all the tested Scottish Fold cats was confirmed, only 1/12 showed clinical signs of SFOCD. Furthermore, no cats in the 1.5-year follow-up showed skeletal changes. Although significant, the c.1024G>T mutation in the TRPV4 gene, supposedly, is not the only cause or risk of developing SFOCD.

The burden of hospital admissions for skeletal dysplasias in Sri Lanka: a population-based study.

BACKGROUND: Skeletal dysplasias are a diverse group of rare disorders in the chondro-osseous tissue that can have a significant impact on patient's functionality. The worldwide prevalence of skeletal dysplasias at birth is approximately 1:5000 births. To date, disease burden and trends of skeletal dysplasias in the Sri Lankan population have not been described in any epidemiological study. Our aim was to evaluate the burden and the current trends in hospital admissions for skeletal dysplasias in the Sri Lankan population. A retrospective evaluation of hospital admissions for skeletal dysplasia during 2017-2020 was performed using population-based data from the eIMMR database which covers government hospitals in the entire country. The trends in hospital admissions for skeletal dysplasias by calendar year, age, and types of skeletal dysplasia were described using appropriate summary statistics. RESULTS: Respective crude admission rates of skeletal dysplasias in the years 2017, 2018, 2019 and 2020 were 5.2, 8.1, 8.0, and 6.5 per million population. A female predominance (1.4:1) was noted during the studied period. Of all reported cases the majority (n = 268; 44.2%) were children less than 4 years. Each year, 0-4 years age group represented 40-47% of the total hospital admissions. More than half of the cases were reported from Colombo (28.1%) and Kandy (25.4%) districts combined. 60% of cases were diagnosed as osteogenesis imperfecta (OI). Rising trends were observed in the hospital admissions for osteogenesis imperfecta, achondroplasia and osteopetrosis, while other skeletal dysplasia types collectively showed a relatively stable trend. CONCLUSION: This preliminary study revealed a female predominance of skeletal dysplasias and a relatively high admission rate of osteogenesis imperfecta in the Sri Lankan population. A distinct trend was not visible in the studied years probably due to the impact on hospital services due to COVID- Pandemic. Future research on the healthcare burden on families affected by skeletal dysplasia is required to better understand the overall cost of care and identify therapies that reduce admission rates. This study highlights the value of analysing population-based data on rare diseases to improve healthcare in low-resource countries.

Cantú syndrome: A new case and evolution of clinical conditions during first 2-year follow-up.

Cantú syndrome, or hypertrichotic osteochondrodysplasia, is a rare autosomal dominant disease characterized by congenital hypertrichosis, characteristic dysmorphisms, skeletal abnormalities and cardiomegaly. We report on a 7-year-old girl with congenital generalized hypertrichosis, coarse facial appearance and cardiac involvement, with a de novo heterozygous mutation (c.3461G > A) in the ABCC9 gene. During the annual cardiac follow-up at the age of nine the echocardiogram showed mild left ventricular dilatation in consideration of which she started ramipril treatment. The progression of the clinical manifestations of Cantú syndrome highlights the relevance of an early diagnosis, including genetic analysis, and a multidisciplinary approach with long-term follow-up.

Pycnodysostosis; A Rare Disease Case Report.

Pycnodysostosis is a rare disease with very few reported cased all over the world. It was first described in 1963 by Maroteaux and Lamy. It is also known as Toulouse-Lautrec syndrome, after a French artist, Henri de Toulouse Lautrec. The affected gene, CTSK, was first isolated in 1996. It is an autosomal recessive osteochondrodysplasia, characterized by disrupted function of osteoclasts. Incidence of this disease is 1.7 per 1 million births with a male to female ratio of 1:1 30% cases arise from consanguineous marriages.

Growth charts in FGFR2- and FGFR3-related faciocraniosynostoses.

Objective: Faciocraniosynostoses (FCS) are malformations affecting the development of the bones of the skull and face, due to the premature closure of one or more craniofacial sutures, mostly secondary to activating Fibroblast Growth Factor Receptor (FGFR) 1-3 mutations. Gain-of-function FGFR3 mutations are also responsible for various conditions referred to as osteochondrodysplasia (OCD), characterized by structural and functional abnormalities of growth plate cartilages. We hypothesized that patients with FGFR-related faciocraniosynostoses may present extra-cranial growth anomalies. Study design: We retrospectively collected height and weight data from a cohort of 70 patients. Included patients were admitted for FGFR-related FCS between 2000 and 2021 at the Craniofacial Unit of Necker - Enfants Malades University Hospital in Paris, France. Results: We showed that FGFR-related faciocraniosynostoses had significantly reduced heights and weights relative to controls, and that two specific time periods (1-3 years and > 8 years of age) were associated with lower height and weight values. Four patients had received growth hormone treatment but remained below normal values for growth in height and weight. Conclusions: Patients with FGFR-related faciocraniosynostoses have clinically significant extra-cranial anomalies which are not currently investigated and managed in usual protocols; these patients could benefit from a systematic pre-pubertal endocrine assessment. More generally, our results extend the scope of extracranial anomalies in FGFR-related faciocraniosynostoses and support the hypothesis that all conditions with activating FGFR mutations affect both membranous ossification and long bones.

A Novel Osteochondrodysplasia With Empty Sella Associates With a TBX2 Variant.

Skeletal dysplasias comprise a heterogenous group of developmental disorders of skeletal and cartilaginous tissues. Several different forms have been described and the full spectrum of their clinical manifestations and underlying genetic causes are still incompletely understood. We report a three-generation Finnish family with an unusual, autosomal dominant form of osteochondrodysplasia and an empty sella. Affected individuals (age range 24-44 years) exhibit unusual codfish-shaped vertebrae, severe early-onset and debilitating osteoarthritis and an empty sella without endocrine abnormalities. Clinical characteristics also include mild dysmorphic features, reduced sitting height ratio, and obesity. Whole-exome sequencing excluded known skeletal dysplasias and identified a novel heterozygous missense mutation c.899C>T (p.Thr300Met) in TBX2, confirmed by Sanger sequencing. TBX2 is important for development of the skeleton and the brain and three prior reports have described variations in TBX2 in patients portraying a complex phenotype with vertebral anomalies, craniofacial dysmorphism and endocrine dysfunctions. Our mutation lies near a previously reported disease-causing variant and is predicted pathogenic with deleterious effects on protein function. Our findings expand the current spectrum of skeletal dysplasias, support the association of TBX2 mutations with skeletal dysplasia and suggest a role for TBX2 in development of the spinal and craniofacial structures and the pituitary gland.

Fetal Skeletal Dysplasias: Radiologic-Pathologic Classification of 72 Cases.

ObjectiveThe aim of this study was to classify the fetal skeletal dysplasias (FSD) in a series of affected fetuses based on radio-pathologic criteria. Materials and methods: We gathered clinicopathologic data of 72 cases which were diagnosed among 5995 autopsies performed over a 8-year period. Results: The prevalence of FSD was 1.2:100 autopsies. The overall sex ratio (M:F) was 1.25. Gestational age was between 17 and 24 weeks in 60% of cases. The FSD were classified into 13 distinct pathologic groups. Four major groups were identified: (1) Osteogenesis imperfecta (21 cases, 29%); (2) FGFR3 chondrodysplasia (18 cases, 25%); (3) Ciliopathies (9 cases, 12%); and (4) Sulfation disorders (7 cases, 10%). Thanatophoric dysplasia type 1 and lethal osteogenesis imperfecta were the most common skeletal dysplasias. Conclusion: Our study demonstrates the usefulness of the radio-pathologic examination in the diagnosis and accurate classification of the FSD, thus enabling better targeting of genetic counseling.

Novel deep intronic and frameshift mutations causing a TRIP11-related disorder.

Mutations of the thyroid hormone receptor interactor 11 gene (TRIP11, OMIM: 604505) at 14q32.12 have been associated with the autosomal recessive achondrogenesis type IA (ACG1A, OMIM: 200600) or osteochondrodysplasia (ODCD, OMIM: 184260). In this clinical report of a Chinese family, the mother had two consecutive pregnancies with similar aberrant phenotypes in the fetuses showing severe limb shortening. Whole exome sequencing (WES) of DNA from the second fetus identified a heterozygous frameshift mutation (NM_004239: c.3852delT) of TRIP11. Although this was consistent with the fetal clinical phenotypes, initial review of the WES results implied another novel mutation. To test this, we used high-precision clinical exome sequencing (HPCES) and found a mutation in Intron 18 of TRIP11 (c.5457+77T>G). Moreover, the sequencing depth of this mutation was only 3× that of WES compared with 161× that by HPCES. To ascertain the pathogenesis of the mutation (c.5457+77T>G), RT-PCR conducted using the parents' blood samples showed a 77-bp intronic sequence in the transcripts, which might have encoded for a shortened protein because of early termination due to code shifting. Our study furthers current understanding of deep intron function and provides a novel diagnostic method of deep intragenic mutations in families having two or more consecutive pregnancies with similar aberrant fetal phenotypes.

Histopathology of recurrent Steel syndrome in fetuses caused by novel variants of COL27A1 gene.

Steel syndrome (STLS) encompasses characteristic facies, dwarfness, irreducible bilateral hip and radial head dislocation, and carpal bone coalition due to COL27A1 mutations. Two consecutive pregnancies in a non-consanguineous couple were terminated because of severe fetal anomalies. Complete autopsies with microscopic exam were performed on both fetuses. Next-generation-based clinical exome sequencing was applied to the first fetus. Exome sequencing results, parental segregation, and affection of the second fetus were confirmed by Sanger sequencing. Both fetuses had signs consistent with STLS. Bilateral capitulum humeri absence explained radial head dislocation in STLS. Metaphyseal cartilage showed severe disorganization. Resting cartilage was hypercellular, organized in irregular nests limited by acellular matrix. Two variants in COL27A1 (c.2548G>A -p.Gly850Arg- and c.3249+1G> T) were found in both fetuses in compound heterozygosity with parental Mendelian segregation. This is the first report to include histology of STLS. The COL27A1 variants here described increase the number of mutations associated with STLS.

Fetal glycosylation defect due to ALG3 and COG5 variants detected via amniocentesis: Complex glycosylation defect with embryonic lethal phenotype.

INTRODUCTION: Congenital disorders of glycosylation (CDG) are inborn errors of glycan metabolism with high clinical variability. Only a few antenatal cases have been described with CDG. Due to a lack of reliable biomarker, prenatal CDG diagnostics relies primarily on molecular studies. In the presence of variants of uncertain significance prenatal glycosylation studies are very challenging. CASE REPORT: A consanguineous couple had a history of second-trimester fetal demise with tetralogy of Fallot and skeletal dysplasia. In the consecutive pregnancy, the second trimester ultrasonography showed skeletal dysplasia, vermian hypoplasia, congenital heart defects, omphalocele and dysmorphic features. Prenatal chromosomal microarray revealed a large region of loss of heterozygosity. Demise occurred at 30 weeks. Fetal whole exome sequencing showed a novel homozygous likely pathogenic variant in ALG3 and a variant of uncertain significance in COG5. METHODS: Western blot was used to quantify ALG3, COG5, COG6, and the glycosylation markers ICAM-1 and LAMP2. RT-qPCR was used for ALG3 and COG5 expression in cultured amniocytes and compared to age matched controls. RESULTS: ALG3 and COG5 mRNA levels were normal. ICAM-1, LAMP2, ALG3 and COG5 levels were decreased in cultured amniocytes, suggesting the possible involvement of both genes in the complex phenotype. CONCLUSION: This is the first case of successful use of glycosylated biomarkers in amniocytes, providing further options of functional antenatal testing in CDG.

Osteochondrodysplasia in Scottish Fold cross-breed cats.

Two Scottish Fold mixed cats are described in this report. Case 1 is a mixed Scottish Fold and Munchkin cat. Extremities of this cat resembled the Munchkin cat, while the ear pinna were folded forward like the Scottish Fold cat. Case 2 is a mixed Scottish Fold and American Curl cat. The ear pinna were curled caudally like the American Curl. Severe exostosis in the hind leg was observed in radiographs taken around one year of age in both cats. Both cats were dominant homozygous for c.1024G>T of the transient receptor potential vanilloid 4 gene, responsible for osteochondrodysplasia in the Scottish Fold cat. Cross breeding with Scottish Fold cats could produce unknown phenotypes, and should be avoided.

A family of Melnick-Needles syndrome: a case report.

BACKGROUND: Melnick-Needles syndrome (MNS) is an extremely rare osteochondrodysplasia caused by a mutation of FLNA, the gene encoding filamin A. MNS is inherited in an X-linked dominant manner. In this study, we describe three members of the same family with MNS, who exhibited different phenotypic severity despite having an identical FLNA gene mutation. CASE PRESENTATION: The patient was 16 months old, with a history of delayed physical development, multiple upper respiratory infections and otitis media episodes. She was referred to our orthopedic clinic because of bowed legs and an abnormal plain chest radiograph. Both upper and lower extremities were bowed. Plain X-rays showed thoracolumbar kyphoscoliosis, with anterior and posterior vertebral scalloping, and thin, wavy ribs. Hypoplasia of the pubis and ischium, with bilateral coxa valga, were also noted. Target exome sequencing revealed a heterozygous mutation of FLNA, c.3578 T > C, p.Lys1193Pro, which confirmed the diagnosis of MNS. Her older sister and mother had minimal deformities of the axial and extremity skeleton, but genetic analyses revealed the same FLNA mutation as the patient. The mutation identified in this family has not been previously reported. CONCLUSION: This report illustrates the potential inherited nature of MNS and the phenotypic variability of clinicoradiologic characteristics. In patients with traits suggestive of MNS, a careful medical and family history should be obtained, and genetic testing should be performed for the patient, as well as all family members.

Fibrodysplasia ossificans progressiva (FOP): A disorder of osteochondrogenesis.

Fibrodysplasia ossificans progressiva (FOP) is an ultra-rare genetic disorder of extraskeletal bone formation, but could appropriately be viewed as a seminal disorder of osteochondrogenesis. Many, if not most, of the musculoskeletal features of FOP are related to dysregulated chondrogenesis including abnormal articular cartilage formation, abnormal diarthrodial joint specification, growth plate dysplasia, osteochondroma formation, heterotopic endochondral ossification (HEO), and precocious arthropathy. In FOP, causative activating mutations of Activin receptor A type I (ACVR1), a bone morphogenetic protein (BMP) type I receptor, are responsible for the osteochondrodysplasia that impacts developmental phenotypes as well as postnatal features of this illustrative disorder. Here, we highlight the myriad developmental and postnatal effects on osteochondrogenesis that emanate directly from mutant ACVR1 and dysregulated bone morphogenetic protein (BMP) signaling in FOP.

National survey of prevalence and prognosis of thanatophoric dysplasia in Japan.

BACKGROUND: Thanatophoric dysplasia (TD) is a rare congenital disease of the skeletal system, with an incidence of 1.68-8.3 per 100 000 births, but statistical data on the estimated number of TD patients across Japan are not available. The aim of this study was therefore to investigate the prevalence and prognosis of TD in Japan. METHODS: A nationwide primary questionnaire survey was conducted. RESULTS: A total of 127 obstetric, 186 pediatric, and 115 orthopedic facilities provided responses. Excluding duplications, we identified 73 patients with TD. Of the 73 cases, 15 were abortions, four were stillbirths, 51 were live births, and three had unknown details. Of the 51 live newborns, 27 died ≤7 days after birth, with an early neonatal mortality rate of 56%. Of the 24 newborns who survived the early neonatal period, 16 survived for ≥1 year. All of the 24 newborns received respiratory management and survived during the early neonatal period. Of the 51 live newborns, 25 did not receive respiratory management and died ≤2 days after birth. CONCLUSIONS: The prevalence of TD in Japan is estimated to be at 1.1 (95%CI: 0.84-1.37) per 100 000 births, but the actual incidence is expected to be higher. To our knowledge, we have confirmed for the first time that newborns with TD may not always die during the early neonatal period but can survive the early neonatal period with appropriate respiratory management. Therefore, the term "thanatophoric dysplasia" does not accurately reflect the nature of the disease.

Mechanistic insights into the cellular effects of a novel FN1 variant associated with a spondylometaphyseal dysplasia.

Spondylometaphyseal dysplasia (SMD) is characterized by developmental changes in long bones and vertebrae. It has large phenotypic diversity and multiple genetic causes, including a recent link to novel variants in the extracellular matrix (ECM) protein fibronectin (FN), a regulator of ECM assembly and key link between the ECM and proper cell function. We identified a patient with a unique SMD, similar to SMD with corner fractures. The patient has been followed over 19 years and presents with short stature, genu varum, kyphoscoliosis, and pectus carinatum. Radiography shows metaphyseal changes that resolved over time, vertebral changes, and capitular avascular necrosis. Whole exome sequencing identified a novel heterozygous FN1 variant (p.Cys97Trp). Using mass spectroscopy, mutant FN was detected in plasma and in culture medium of primary dermal fibroblasts isolated from the patient, but mutant protein was much less abundant than wild-type FN. Immunofluorescence and immunoblotting analyses show that mutant fibroblasts assemble significantly lower amounts of FN matrix than wild-type cells, and mutant FN was preferentially retained within the endoplasmic reticulum. This work highlights the importance of FN in skeletal development, and its potential role in the pathogenesis of a subtype of SMD.

Piepkorn type of osteochondrodysplasia: Defining the severe end of FLNB-related skeletal disorders in three fetuses and a 106-year-old exhibit.

The Piepkorn type of lethal osteochondrodysplasia (POCD) is a rare and lethal dwarfing condition. Four cases have been reported to date. The characteristic features are distinctly shortened "flipper-like" limbs, polysyndactyly, excessive underossification, especially of the limb bones and vertebrae, and large (giant) chondrocytes in the cartilaginous bone primordia. These characteristics allowed the diagnosis of Piepkorn type of osteochondrodysplasia in four new cases, three fetuses of 15 to 22 weeks and one 106-year-old museum exhibit. Piepkorn type of osteochondrodysplasia has been assigned to the giant cell chondrodysplasias such as atelosteogenesis type 1 (AO1) and boomerang dysplasia (BD). Analysis of the Filamin B gene in 3p14.3, which is associated with these disorders, allowed the identification of the first FLNB mutations in Piepkorn type of osteochondrodysplasia. The heterozygous missense mutations, found in the three fetuses, were located in exons 28 and 29, encoding the immunoglobulin-like repeat region R15, one of three mutational hot spots in dominant FLNB-related skeletal disorders. Direct preparations and alcian blue staining revealed single upper and lower arm and leg bone primordia, preaxial oligodactyly, and polysyndactyly with complete fusion and doubling of the middle and end phalanges II-V to produce eight distal finger rays. Considering the unique clinical features and the extent of underossification, Piepkorn type of osteochondrodysplasia can be regarded as a distinct entity within the AO1-BD-POCD continuum.

A review of skeletal dysplasia research in India.

We aimed to review the contributions by Indian researchers to the subspecialty of skeletal dysplasias (SDs). Literature search using specific keywords in PubMed was performed to retrieve all the published literature on SDs as on July 6, 2017. All published literature on SDs wherein at least one author was from an Indian institute was included. Publications were grouped into different categories based on the major emphasis of the research paper. Five hundred and forty publications in English language were retrieved and categorized into five different groups. The publications were categorized as reports based on: (i) phenotypes (n = 437), (ii) mutations (n = 51), (iii) novel genes (n = 9), (iv) therapeutic interventions (n = 31), and (v) reviews (n = 12). Most of the publications were single-patient case reports describing the clinical and radiological features of the patients affected with SDs (n = 352). We enlisted all the significant Indian contributions. We have also highlighted the reports in which Indians have contributed to discovery of new genes and phenotypes. This review highlights the substantial Indian contributions to SD research, which is poised to reach even greater heights given the size and structure of our population, technological advances, and expanding national and international collaborations.