Spondyloepimetaphyseal dysplasia-Maroteaux type due to dominant TRPV4 mutation: expanding the phenotype with a case report.

INTRODUCTION: Dominant pathogenic mutations in the TRPV4 gene give rise to a wide spectrum of abnormal phenotypes, including bone dysplasia as well as spinal muscular atrophy and hereditary motor and sensory neuropathy. Spondyloepimetaphyseal dysplasias (SEMDs) are autosomal dominant skeletal dysplasias characterized by mild epiphyseal dysplasia, flared metaphyses, prominent joints, spondyler dysplasia, and brachydactyly with various carpal, metacarpal, and finger malformations. CASE PRESENTATION: We present a boy who has the clinical and radiological signs of SEMD-M with a dominant TRPV4 mutation. He also has some striking findings that have not been seen in these patients before, and they may be able to provide assistance to medical professionals in the process of diagnosis.These include a shorter distance between his lumbar vertebrae, congenital contractures, and an arachnoid cyst.

Secondary osteosarcoma associated with osteofibrous dysplasia: a case report.

Secondary osteosarcoma is a rare complication of primary malignancies and benign bone lesions. There are various types of diseases that cause secondary osteosarcoma. A 15-year-old male presented at our medical center complaining of pain and redness in the right lower leg. He had been diagnosed with osteofibrous dysplasia in the right tibia when he was 2 years old and since then had been followed up. Although he had a pathological fracture of the right tibia at the age of 7, his fracture healed with a plaster cast and did not require surgery. At the time of the patient's last visit, a radiograph revealed a periosteal reaction as well as erosion of the bone cortex. Magnetic resonance imaging revealed an infiltrative area in the soft tissue surrounding the osteofibrous dysplasia lesion in the tibia. Consequent to pathological examination (through bone biopsy), the patient was diagnosed with secondary osteosarcoma. The patient underwent chemotherapy and extensive resection with liquid nitrogen. He has been progressing satisfactorily after the operation. The present case is the first report of secondary osteosarcoma associated with osteofibrous dysplasia. During the long-term follow-up of osteofibrous dysplasia, oncologists should be aware of the possibility of secondary osteosarcoma.

Treatment of Dysplasia Epiphysealis Hemimelica with Autologous Chondrocyte Implantation: A Case Report.

Case: We present a case of dysplasia epiphysealis hemimelica (DEH) involving the posteromedial distal femur in a 4-year-old girl. The patient underwent lesion resection with internal fixation of the articular cartilage followed by autologous chondrocyte implantation (ACI) to restore the articular surface and epiphysis. At the 7-year follow-up, the patient had no pain or difficulty with participation in sports. Advanced imaging showed a stable articular surface with evidence of durable cartilage integration. Conclusion: DEH is a rare disease often treated by resection. In cases where the articular surface of the knee is involved, we have demonstrated that augmentation with ACI can be an effective treatment option.

Clinical and Molecular Diagnosis of Osteocraniostenosis in Fetuses and Newborns: Prenatal Ultrasound, Clinical, Radiological and Pathological Features.

Osteocraniostenosis (OCS, OMIM #602361) is a severe, usually lethal condition characterized by gracile bones with thin diaphyses, a cloverleaf-shaped skull and splenic hypo/aplasia. The condition is caused by heterozygous mutations in the FAM111A gene and is allelic to the non-lethal, dominant disorder Kenny-Caffey syndrome (KCS, OMIM #127000). Here we report two new cases of OCS, including one with a detailed pathological examination. We review the main diagnostic signs of OCS both before and after birth based on our observations and on the literature. We then review the current knowledge on the mutational spectrum of FAM111A associated with either OCS or KCS, including three novel variants, both from one of the OCS fetuses described here, and from further cases diagnosed at our centers. This report refines the previous knowledge on OCS and expands the mutational spectrum that results in either OCS or KCS.

Identification and Functional Evaluation of a Novel TBX4 Mutation Underlies Small Patella Syndrome.

Small patella syndrome (SPS) is a rare autosomal dominant disorder caused by mutations in TBX4 gene which encodes a transcription factor of FGF10. However, how TBX4 mutations result in SPS is poorly understood. Here, a novel TBX4 mutation c.1241C>T (p.P414L) was identified in a SPS family and series of studies were performed to evaluate the influences of TBX4 mutations (including c.1241C>T and two known mutations c.256G>C and c.743G>T). Results showed that mesenchymal stem cells (MSCs) with stable overexpression of either TBX4 wild-type (TBX4wt) or mutants (TBX4mt) were successfully generated. Immunofluorescence study revealed that both the overexpressed TBX4 wild-type and mutants were evenly expressed in the nucleus suggesting that these mutations do not alter the translocation of TBX4 into the nucleus. Interestingly, MSCs overexpression of TBX4mt exhibited reduced differentiation activities and decreased FGF10 expression. Chromatin immunoprecipitation (ChIP) study demonstrated that TBX4 mutants still could bind to the promoter of FGF10. However, dual luciferase reporter assay clarified that the binding efficiencies of TBX4 mutants to FGF10 promoter were reduced. Taken together, MSCs were firstly used to study the function of TBX4 mutations in this study and the results indicate that the reduced binding efficiencies of TBX4 mutants (TBX4mt) to the promoter of FGF10 result in the abnormal biological processes which provide important information for the pathogenesis of SPS.

Osteofibrous dysplasia of the tibia : the importance of deformity in surveillance.

AIMS: Osteofibrous dysplasia (OFD) is a rare benign lesion predominantly affecting the tibia in children. Its potential link to adamantinoma has influenced management. This international case series reviews the presentation of OFD and management approaches to improve our understanding of OFD. METHODS: A retrospective review at three paediatric tertiary centres identified 101 cases of tibial OFD in 99 patients. The clinical records, radiological images, and histology were analyzed. RESULTS: Mean age at presentation was 13.5 years (SD 12.4), and mean follow-up was 5.65 years (SD 5.51). At latest review, 62 lesions (61.4%) were in skeletally mature patients. The most common site of the tibial lesion was the anterior (76 lesions, 75.2%) cortex (63 lesions, 62.4%) of the middle third (52 lesions, 51.5%). Pain, swelling, and fracture were common presentations. Overall, 41 lesions (40.6%) presented with radiological deformity (> 10°): apex anterior in 97.6%. A total of 41 lesions (40.6%) were treated conservatively. Anterior bowing < 10° at presentation was found to be related to successful conservative management of OFD (p = 0.013, multivariable logistic regression). Intralesional excision was performed in 43 lesions (42.6%) and a wide excision of the lesion in 19 (18.8%). A high complication rate and surgical burden was found in those that underwent a wide excision regardless of technique employed. There was progression/recurrence in nine lesions (8.9%) but statistical analysis found no predictive factors. No OFD lesion transformed to adamantinoma. CONCLUSION: This study confirms OFD to be a benign bone condition with low rates of local progression and without malignant transformation. It is important to distinguish OFD from adamantinoma by a histological diagnosis. Focus should be on angular deformity, monitored with full-length tibial radiographs. Surgery is indicated in symptomatic patients and predicted by the severity of the initial angular deformity. Surgery should focus more on the deformity rather than the lesion. Cite this article: Bone Joint J 2022;104-B(2):302-308.

Significant Asymmetry of the Bilateral Upper Extremities of a Skeleton Excavated from the Mashiki-Azamabaru Site, Okinawa Island, Japan.

The human skeleton of a young adult male with marked asymmetry of the bilateral upper extremities was excavated from the Mashiki-Azamabaru site (3000-2000 BCE) on the main island of Okinawa in the southwestern archipelago of Japan. The skeleton was buried alone in a corner of the cemetery. In this study, morphological and radiographic observations were made on this skeleton, and the pathogenesis of the bone growth disorder observed in the left upper limb was discussed. The maximum diameter of the midshaft of the humerus was 13.8 mm on the left and 21.2 mm on the right. The long bones comprising the left upper extremity lost the structure of the muscle attachments except for the deltoid tubercle of the humerus. The bone morphology of the right upper extremity and the bilateral lower extremities was maintained and was close to the mean value of females from the Ohtomo site in northwestern Kyushu, Japan, during the Yayoi period. It is assumed that the anomalous bone morphology confined to the left upper extremity was secondary to the prolonged loss of function of the muscles attached to left extremity bones. In this case, birth palsy, brachial plexus injury in childhood, and acute grey matter myelitis were diagnosed. It was suggested that this person had survived into young adulthood with severe paralysis of the left upper extremity due to injury or disease at an early age.

Dysplasia Epiphysealis Hemimelica Presenting as Multiple Loose Bodies: A Case Report.

CASE: A 11-year-old boy with no medical history presented with a protective limp and worsening mechanical pain in his left knee. No recent traumatic or infectious history was reported. Radiographs and ultrasonography showed multiple intra-articular loose bodies with osteocartilaginous signal. Dysplasia epiphysealis hemimelica (DEH) was confirmed by magnetic resonance imaging (MRI) and computed tomography (CT) scan. This is the first report that describes the presence of loose bodies in a knee without previous surgery as a possible case of DEH. CONCLUSION: We emphasize the use of CT scan and MRI before any surgical procedure when intra-articular loose bodies are unexpectedly discovered.

Acrocapitofemoral dysplasia: Novel mutation in IHH in two adult patients from the third family in the literature and progression of the disease.

Acrocapitofemoral dysplasia (ACFD) is a rare autosomal recessive skeletal dysplasia characterized by short stature with short limb dwarfism, brachydactyly, and a narrow thorax. Major radiographic features are egg-shaped capital femoral epiphyses with a short femoral neck and cone-shaped epiphyses, mainly in the hands and hips. To date, only four child patients from two families have been reported. We describe two adult patients with ACFD with a novel homozygous c.478C>T (p.Arg160Cys) mutation in IHH in the third family of the literature. The reported cases showed a middle phalanges which fused with distal phalanges in the fifth toes, the typical configuration of metacarpals, radial angulation and extremely short femoral neck. These findings could help the diagnosis of ACFD in adult patients. We hope that this new family will be a helpful guide for predicting and managing the prognosis of diagnosed children.

TMEM263: a novel candidate gene implicated in human autosomal recessive severe lethal skeletal dysplasia.

INTRODUCTION: Skeletal dysplasia is a common, clinically and genetically heterogeneous disorder in the human population. An increasing number of different genes are being identified causing this disorder. We used whole exome sequencing (WES) for detection of skeletal dysplasia causing mutation in a fetus affected to severe lethal skeletal dysplasia. PATIENT: Fetus was assessed by ultrasonography in second trimester of pregnancy. He suffers from severe rhizomelic dysplasia and also pathologic shortening of ribs. WES was applied to finding of causal mutation. Furthermore, bioinformatics analysis was performed to predict mutation impact. RESULTS: Whole exome sequencing (WES) identified a homozygous frameshift mutation in the TMEM263 gene in a fetus with severe lethal skeletal dysplasia. Mutations of this gene have been previously identified in dwarf chickens, but this is the first report of involvement of this gene in human skeletal dysplasia. This gene plays a key role in the growth hormone signaling pathway. CONCLUSION: TMEM263 can be considered as a new gene responsible for skeletal dysplasia. Given the complications observed in the affected fetus, the mutation of this gene appears to produce much more intense complications than that found in chickens and is likely to play a more important role in bone development in human.

Acromesomelic dysplasia-Maroteaux type, nine patients with two novel NPR2 variants.

OBJECTIVES: Acromesomelic dysplasia, type Maroteaux, is an autosomal recessive skeletal dysplasia caused by biallelic loss of function variations of NPR2, which encodes a cartilage regulator C-type natriuretic peptide receptor B. NPR2 variations impair skeletal growth. It is a rare type of dwarfism characterized by shortening of the middle and distal segments of the limbs with spondylar dysplasia. METHODS: We performed detailed clinical and radiological evaluation and sequence analysis for NPR2. RESULTS: Herein, we report nine patients from eight families with two novel NPR2 pathogenic variants. CONCLUSIONS: This study describes typical clinical phenotypes of Maroteaux type acromesomelic dysplasia, and enriches the variant spectrum of NPR2 by reporting one nonsense and one missense novel variant. We emphasize the importance of detailed clinical evaluation before genetic testing in diagnosing rare skeletal disorders.

The role of biomineralization in disorders of skeletal development and tooth formation.

The major mineralized tissues are bone and teeth, which share several mechanisms governing their development and mineralization. This crossover includes the hormones that regulate circulating calcium and phosphate concentrations, and the genes that regulate the differentiation and transdifferentiation of cells. In developing endochondral bone and in developing teeth, parathyroid hormone-related protein (PTHrP) acts in chondrocytes to delay terminal differentiation, thereby increasing the pool of precursor cells. Chondrocytes and (in specific circumstances) pre-odontoblasts can also transdifferentiate into osteoblasts. Moreover, bone and teeth share outcomes when affected by systemic disorders of mineral homeostasis or of the extracellular matrix, and by adverse effects of treatments such as bisphosphonates and fluoride. Unlike bone, teeth have more permanent effects from systemic disorders because they are not remodelled after they are formed. This Review discusses the normal processes of bone and tooth development, followed by disorders that have effects on both bone and teeth, versus disorders that have effects in one without affecting the other. The takeaway message is that bone specialists should know when to screen for dental disorders, just as dental specialists should recognize when a tooth disorder should raise suspicions about a possible underlying bone disorder.

High diagnostic yield in skeletal ciliopathies using massively parallel genome sequencing, structural variant screening and RNA analyses.

Skeletal ciliopathies are a heterogenous group of disorders with overlapping clinical and radiographic features including bone dysplasia and internal abnormalities. To date, pathogenic variants in at least 30 genes, coding for different structural cilia proteins, are reported to cause skeletal ciliopathies. Here, we summarize genetic and phenotypic features of 34 affected individuals from 29 families with skeletal ciliopathies. Molecular diagnostic testing was performed using massively parallel sequencing (MPS) in combination with copy number variant (CNV) analyses and in silico filtering for variants in known skeletal ciliopathy genes. We identified biallelic disease-causing variants in seven genes: DYNC2H1, KIAA0753, WDR19, C2CD3, TTC21B, EVC, and EVC2. Four variants located in non-canonical splice sites of DYNC2H1, EVC, and KIAA0753 led to aberrant splicing that was shown by sequencing of cDNA. Furthermore, CNV analyses showed an intragenic deletion of DYNC2H1 in one individual and a 6.7 Mb de novo deletion on chromosome 1q24q25 in another. In five unsolved cases, MPS was performed in family setting. In one proband we identified a de novo variant in PRKACA and in another we found a homozygous intragenic deletion of IFT74, removing the first coding exon and leading to expression of a shorter message predicted to result in loss of 40 amino acids at the N-terminus. These findings establish IFT74 as a new skeletal ciliopathy gene. In conclusion, combined single nucleotide variant, CNV and cDNA analyses lead to a high yield of genetic diagnoses (90%) in a cohort of patients with skeletal ciliopathies.

Report of a novel variant in the FAM111A gene in a fetus with multiple anomalies including gracile bones, hypoplastic spleen, and hypomineralized skull.

Kenny-Caffey syndrome type 2 (KCS2) and osteocraniostenosis (OCS) are allelic disorders caused by heterozygous pathogenic variants in the FAM111A gene. Both conditions are characterized by gracile bones, characteristic facial features, hypomineralized skull with delayed closure of fontanelles and hypoparathyroidism. OCS and KCS2 are often referred to as FAM111A-related syndromes as a group; although OCS presents with a more severe, perinatal lethal phenotype. We report a novel FAM111A mutation in a fetus with poorly ossified skull, proportionate long extremities with thin diaphysis, and hypoplastic spleen consistent with FAM111A-related syndromes. Trio whole exome sequencing identified a p.Y562S de novo missense variant in the FAM111A gene. The variant shows significant similarity to other reported pathogenic mutations fitting proposed pathophysiologic mechanism which provide sufficient evidence for classification as likely pathogenic. Our report contributed a novel variant to the handful of OCS and KCS2 cases reported with pathogenic variants.

Natural history of TRPV4-Related disorders: From skeletal dysplasia to neuromuscular phenotype.

TRPV4-related disorders constitute a broad spectrum of clinical phenotypes including several genetic skeletal and neuromuscular disorders, in which clinical variability and somewhat overlapping features are present. These disorders have previously been considered to be clinically distinct phenotypes before their molecular basis was discovered. However, with the identification of TRPV4 variants in the etiology, they are referred as TRPV4-related disorders (TRPV4-pathies), and are now mainly grouped into skeletal dysplasias and neuromuscular disorders. The skeletal dysplasia group includes metatropic dysplasia, parastremmatic dysplasia, spondyloepiphyseal dysplasia Maroteaux type, spondylometaphyseal dysplasia Kozlowski type, autosomal dominant brachyolmia, and familial digital arthropathy-brachydactyly, whereas the neuromuscular group includes congenital distal spinal muscular atrophy (SMA), scapuloperoneal SMA and Charcot-Marie-Tooth neuropathy type 2C with common manifestations of peripheral neuropathy, joint contractures, and respiratory system involvement. Apart from familial digital arthropathy-brachydactyly, skeletal dysplasia associated with TRPV4 pathogenic variants share some clinical features such as short stature with short trunk, spinal and pelvic changes with varying degrees of long bone involvement. Of note, there is considerable phenotypic overlap within and between both groups. Herein, we report on the clinical and molecular spectrum of 11 patients from six different families diagnosed with TRPV4-related disorders. This study yet represents the largest cohort of patients with TRPV4 variants from a single center in Turkey.

Vertebral deformities in interspecific diploid and triploid salmonid hybrids.

Vertebral deformities in salmonid interspecific hybrids, some of which were triploidised, were assessed across three separate year classes during the freshwater life stage. Initially, eggs from a farmed Atlantic salmon Salmo salar were crossed with the sperm from a S. salar, arctic char Salvelinus alpinus or brown trout Salmo trutta. For S. salar × S. trutta, half the eggs were triploidised. In a second- and third-year class, the eggs from a farmed S. salar were crossed with the sperm from either a S. salar or a S. trutta, and half of each group was triploidised. In the two initial-year classes, all hybrids were larger than the S. salar controls, and triploid S. salar × S. trutta were larger than diploid counterparts. In the third-year class, the S. salar × S. trutta were smaller than the S. salar, in contrast to the initial 2 year classes, although the triploid hybrids were still larger than the diploids. In the third-year class, a high degree of spontaneous triploidy was also observed in the putative diploid groups (between 16 and 39%). Vertebral deformities were consistently higher in pressure-shocked triploids than diploids, irrespective of hybridisation, but there was no consistent effect of hybridisation among experiments. Although this study was not able to explain the contrasting results for vertebral deformities between year classes, triploid S. salar × S. trutta can demonstrate impressive freshwater growth that could be of interest for future farming programmes.

Skeletal deformities in wild and farmed cleaner fish species used in Atlantic salmon Salmo salar aquaculture.

As a first attempt to assess bone health in cleaner fish production, wild and cultured ballan wrasse Labrus bergylta and lumpfish Cyclopterus lumpus were examined by radiology. In C. lumpus, wild fish (57%) had more vertebra deformities (≥1 deformed vertebrae) than cultured fish (2-16%). One wild C. lumpus had lordosis and another was missing the tail fin. In L. bergylta, wild fish (11%) had fewer vertebra deformities than cultured individuals (78-91%). Among the cultured L. bergylta, 17-53% of the fish had severe vertebra deformities (≥6 deformed vertebrae) with two predominate sites of location, one between vertebra 4 and 10 (S1) in the trunk, and one between 19 and 26 (S2) in the tail. Fusions dominated S1, while compressions dominated S2. Although wild L. bergylta had a low vertebra deformity level, 83% had calluses and 14% had fractures in haemal/neural spines and/or ribs. The site-specific appearance and pathology of fracture and callus in wild L. bergylta suggests these are induced by chronic mechanical stress, and a possible pathogenesis for fish hyperostosis is presented based on this notion. In conclusion, good bone health was documented in cultured C. lumpus, but cultured L. bergylta suffered poor bone health. How this affects survival, growth, swimming abilities and welfare in cultured wrasse should be further investigated. SIGNIFICANCE STATEMENT: Skeletal deformities were studied in ballan wrasse and lumpfish of both wild and cultured origin for the first time to identify potential welfare issues when deploying them as cleaner fish in salmon sea cages. While cultured lumpfish showed good bone health, cultured wrasse had a high occurrence of vertebra deformities, which is expected to impact lice eating efficiency and animal welfare negatively. These deformities are most likely induced early in development.

Fibrous dysplasia limited to an ossicle.

Fibrous dysplasia is an unusual pathologic condition caused by abnormal bone metabolism. Temporal bone involvement is often seen, but it is uncommon to find fibrous dysplasia limited to the middle ear, especially originating in and confined to a single ossicle. Here we report a case of osteofibrous dysplasia limited exclusively to an ossicle (malleus) causing gradual conductive hearing loss, which recovered after eventual complete removal of the dysplastic area. The lesion showed firm attachment to adjacent structures and initial removal was not possible. This report provides information to help other otologic surgeons facing similar conditions.

Novel form of rhizomelic skeletal dysplasia associated with a homozygous variant in GNPNAT1.

BACKGROUND: Studies exploring molecular mechanisms underlying congenital skeletal disorders have revealed novel regulators of skeletal homeostasis and shown protein glycosylation to play an important role. OBJECTIVE: To identify the genetic cause of rhizomelic skeletal dysplasia in a consanguineous Pakistani family. METHODS: Clinical investigations were carried out for four affected individuals in the recruited family. Whole genome sequencing (WGS) was completed using DNA from two affected and two unaffected individuals from the family. Sequencing data were processed, filtered and analysed. In silico analyses were performed to predict the effects of the candidate variant on the protein structure and function. Small interfering RNAs (siRNAs) were used to study the effect of Gnpnat1 gene knockdown in primary rat chondrocytes. RESULTS: The patients presented with short stature due to extreme shortening of the proximal segments of the limbs. Radiographs of one individual showed hip dysplasia and severe platyspondyly. WGS data analyses identified a homozygous missense variant c.226G>A; p.(Glu76Lys) in GNPNAT1, segregating with the disease. Glucosamine 6-phosphate N-acetyltransferase, encoded by the highly conserved gene GNPNAT1, is one of the enzymes required for synthesis of uridine diphosphate N-acetylglucosamine, which participates in protein glycosylation. Knockdown of Gnpnat1 by siRNAs decreased cellular proliferation and expression of chondrocyte differentiation markers collagen type 2 and alkaline phosphatase, indicating that Gnpnat1 is important for growth plate chondrocyte proliferation and differentiation. CONCLUSIONS: This study describes a novel severe skeletal dysplasia associated with a biallelic, variant in GNPNAT1. Our data suggest that GNPNAT1 is important for growth plate chondrogenesis.