Sulfate: a neglected (but potentially highly relevant) anion

Sulfate is an important anion as sulfonation is essential in modulation of several compounds, such as exogens, polysaccharide chains of proteoglycans, cholesterol or cholesterol derivatives and tyrosine residues of several proteins. Sulfonation requires the presence of both the sulfate donor 3'-phosphoadenosine-5'-phosphosulfate (PAPS) and a sulfotransferase. Genetic disorders affecting sulfonation, associated with skeletal abnormalities, impaired neurological development and endocrinopathies, demonstrate the importance of sulfate. Yet sulfate is not measured in clinical practice. This review addresses sulfate metabolism and consequences of sulfonation defects, how to measure sulfate and why we should measure sulfate more often.

Aggrecan-related bone disorders; a novel heterozygous ACAN variant associated with spondyloepimetaphyseal dysplasia expanding the phenotypic spectrum and review of literature

BACKGROUND

Spondyloepimetaphyseal dysplasias (SEMD) are a large group of skeletal disorders represented by abnormalities of vertebrae in addition to epiphyseal and metaphyseal areas of bones. Several genes have been identified underlying different forms. ACAN gene mutations were found to cause Aggrecan-related bone disorders (spondyloepimetaphyseal dysplasias,spondyloepiphyseal dysplasias, familial osteochondritis dissecans and short stature syndromes). This study aims to find the disease causing variant in Egyptian patient with SEMD using whole exome sequencing.

METHODS

Whole-exome sequencing was performed for an Egyptian male patient who presented with short stature, clinical and radiological features suggestive of unclassified SEMD.

RESULTS

The study identified a novel de novo heterozygous ACAN gene variant (c.7378G>A; p.Gly2460Arg) in G3 domain. Mutations in ACAN gene have been more commonly associated with short stature than SEMD. The phenotype of our patient was intermediate in severity between spondyloepiphyseal dysplasia presentation; Kimberley type(SEDK) and Spondyloepimetaphyseal dysplasias Aggrecan (SEMDAG) CONCLUSIONS: Whole exome sequencing revealed a novel de novo ACAN gene variant in patient with SEDK. The clinical and skeletal phenotype of our patient was much severe than those reported originally and showed more metaphyseal involvement. To the best of our knowledge, two previous studies reported a heterozygous variant in ACAN with spondyloepiphyseal dysplasia presentation; Kimberley type.

Primary cilia in skeletal development and disease

Primary cilia are non-motile, microtubule-based sensory organelle present in most vertebrate cells with a fundamental role in the modulation of organismal development, morphogenesis, and repair. Here we focus on the role of primary cilia in embryonic and postnatal skeletal development. We examine evidence supporting its involvement in physiochemical and developmental signaling that regulates proliferation, patterning, differentiation and homeostasis of osteoblasts, chondrocytes, and their progenitor cells in the skeleton. We discuss how signaling effectors in mechanotransduction and bone development, such as Hedgehog, Wnt, Fibroblast growth factor and second messenger pathways operate at least in part at the primary cilium. The relevance of primary cilia in bone formation and maintenance is underscored by a growing list of rare genetic skeletal ciliopathies. We collate these findings and summarize the current understanding of molecular factors and mechanisms governing primary ciliogenesis and ciliary function in skeletal development and disease.

Imaging studies used as aid in the diagnosis of cleidocranial dysplasia. A review

Cleidocranial dysplasia (CCD), also known as Marie-Sainton syndrome, is a rare disorder of autosomal dominant type that presents specific characteristics at the skeletal and dental level. The diagnosis of CCD is based on clinical and radiographic findings. Panoramic, cephalometric and anterior poster radiographs have been used for its diagnosis in dentistry. However, these radiological techniques have limitations, and advances in technology with new imaging studies such as magnetic resonance imaging (MRI) and ultrasound have emerged, contributing to the diagnosis of CCD. Therefore, the aim of this review was to identify and describe current imaging studies that contribute to both the diagnosis and adequate and efficient treatment planning of CCD, and describe the clinical and radiographic characteristics of patients with this syndrome.

[Rare bone disorders and respective treatments]

Delineating the genetic background and the underlying pathophysiology of rare skeletal dysplasias enables a broader understanding of these disorders as well as novel perspectives regarding differential diagnosis and targeted development of therapeutic approaches. Hypophosphatasia (HPP) due to genetically determined Alkaline Phosphatase deficiency exemplifies this development. While an enzyme replacement therapy could be established for severe HPP with the prevailing bone manifestation, the clinical impact of not immediately bone-related manifestations just being successively understood. Correspondingly, the elucidation of the pathophysiology underlying renal phosphate wasting expanded our knowledge regarding phosphate metabolism and bone health and facilitated the development of an anti-FGF-23 Antibody for targeted treatment of X‑linked Hypophosphatemia (XLH). Evolutions regarding the nosology of osteogenesis imperfecta (OI) along with the identification of further causative genes also detected in the context of genetically determined osteoporosis illustrate the pathophysiologic interrelation between monogenetic bone dysplasias and multifactorial osteoporosis. While current therapeutic strategies for OI follow osteoporosis treatment, the expanding knowledge about OI forms the fundament for establishing improved treatment strategies-for both OI and osteoporosis. Similar developments are emerging regarding rare skeletal disorders like Achondroplasia, Fibrodysplasia ossificans progressive and Morbus Morquio (Mukopolysaccharidosis Type IV).

Genetics for paediatric radiologists

An understanding of genetics and genomics is increasingly important for all clinicians. Next-generation genomic sequencing technologies enable sequencing of the entire human genome in short timescales, and are increasingly being implemented in health care systems. Clinicians across all medical specialties will increasingly use results generated from genomic testing to inform their clinical practice and provide the best quality of care for patients. These innovations are already transforming the diagnostic pathways for rare genetic diseases, including skeletal dysplasias, with an inevitable impact on the traditional roles of diagnosticians. This article covers the fundamentals of human genetics, mechanisms of genetic variation and the technologies used to investigate the genetic basis of disease, with a specific focus on skeletal dysplasias and the potential impact of genomics on paediatric radiology.

Prenatal diagnosis of skeletal dysplasias using whole exome sequencing in China

BACKGROUND

Skeletal dysplasias account for nearly 10% of fetal structural malformations detected by ultrasonography. This clinically heterogeneous group of genetic anomaly includes at least 461 genetic skeletal disorders with extreme clinical, phenotypic, and genetic heterogeneities, thus, significantly complicates accurate diagnosis. Researches have used whole exome sequencing (WES) for prenatal molecular diagnoses of skeletal dysplasias, however, data are still limited.

METHODS

DNA extracted from umbilical cord blood or amniocytes from fetuses suspected of skeletal dysplasias based on ultrasound evaluations were analyzed by WES. Blood samples were taken from the parents of the positive fetuses for co-segregation analysis using Sanger sequencing.

RESULT

Definitive molecular diagnosis was made in 6/8 (75%) cases, comprised of 5 de novo disease-causing changes in 3 genes (FGFR3, COL2A1, and COL1A2) and one proband with a biallelic deficiency for Lamin B Receptor(LBR),and including 3 novel variants. All fetuses had no detectable copy number variation (CNV) from sequencing results.

CONCLUSIONS

Our study suggests that WES is an efficient approach for prenatal diagnosis of fetuses suspected of skeletal abnormalities and contributes to parental genetics counseling and pregnancy management.

Progressive pseudorheumatoid dysplasia: a report of three cases and a review of radiographic and magnetic resonance imaging findings

Progressive pseudorheumatoid dysplasia (PPD) is a rare disorder of postnatal skeletal and cartilage development that often presents with similar clinical findings to juvenile idiopathic arthritis. Patients with PPD display findings of progressive cartilage loss and secondary osteoarthritis over serial imaging studies and have an absence of elevation of inflammatory markers. Awareness of the imaging features of PPD on radiographs and magnetic resonance imaging (MRI) may be important for early diagnosis and surveillance of the disease.

Skeletal Dysplasias: What Every Bone Health Clinician Needs to Know

PURPOSE OF REVIEW

This review highlights how skeletal dysplasias are diagnosed and how our understanding of some of these conditions has now translated to treatment options.

RECENT FINDINGS

The use of multigene panels, using next-generation sequence technology, has improved our ability to quickly identify the genetic etiology, which can impact management. There are successes with the use of growth hormone in individuals with SHOX deficiencies, asfotase alfa in hypophosphatasia, and some promising data for c-type natriuretic peptide for those with achondroplasia. One needs to consider that a patient with short stature has a skeletal dysplasia as options for management may be available.

Genomic approaches to diagnose rare bone disorders

Skeletal dysplasias are Mendelian disorders with a prevalence of approximatively 1 in every 5000 individuals and can usually be diagnosed based on clinical and radiological findings. However, given that some diseases can be caused by several different genes, and that some genes can cause a variety of different phenotypes, achieving a molecular diagnosis can be challenging. We review here different approaches, from single gene sequencing to genomic approaches using next-generation sequencing, to reach a molecular diagnosis for skeletal dysplasias. We will further describe the overall advantages and limitations of first, second and third-generation sequencing, including single gene sequencing, whole-exome and genome sequencing (WES and WGS), multiple gene panel sequencing and single molecule sequencing. We also provide a brief overview of potential future applications of emerging technologies.

Skeletal dysplasias

The skeletal dysplasias are a group of more than 450 heritable disorders of bone. They frequently present in the newborn period with disproportion, radiographic abnormalities, and occasionally other organ system abnormalities. For improved clinical care, it is important to determine a precise diagnosis to aid in management, familial recurrence, and identify those disorders highly associated with mortality. Long-term management of these disorders is predicated on an understanding of the associated skeletal system abnormalities, and these children are best served by a team approach to health care surveillance.