Search

Background: The osteosclerotic skeletal dysplasias (OSSDs) are a heterogeneous group of disorders characterized by systemic bone sclerosis. Little is known about OSSDs because of their rarity. We conducted a cross-sectional nationwide survey of OSSDs and examined the incidence, epidemiology, and therapeutic interventions on these disorders., Methods: This study consisted of a two-step survey. The number of patients with OSSDs who had visited medical institutions between April 2017 and March 2018 was reported from a total of 341 facilities (1364 departments from pediatrics, orthopaedic surgery, neurosurgery, and otolaryngology in each facility) by the first questionnaire. In the secondary survey, their clinical features were assessed by collecting demographic data, diagnostic details, current status, family histories, therapeutic interventions, histories of bone fracture and osteomyelitis, severity assessed by the modified Rankin Scale (mRS) and recent lifestyle conditions of the patient by the EQ-5D., Results: In the first survey, 51 facilities (56 departments) reported one or more OSSDs patients, including 50 patients with osteopetrosis and 57 patients of other OSSDs. Among 87 patients eligible for inclusion in the analysis in the secondary survey, we investigated detailed information on the 42 patients with osteopetrosis. The number of initial visits of osteopetrosis patients during the surveillance period was five per year, indicating that the estimated incidence of osteopetrosis seemed to be 0.6 per 100,000 live births. Eighty-six bone fractures were reported in 22 patients (52%), and interventions of pseudarthrosis were conducted in five patients. Nine patients (23%) showed significant disabilities with the mRS of grade 3 or higher. Neurological complications and severe anemia were the factors that deteriorate patients' quality of life., Conclusions: This is the first study to examine the detailed epidemiology of OSSDs in Japan. We demonstrated that the incidence of OSSDs is extremely rare. Bone fragility and delayed fracture healing seem to be important orthopaedic problems for patients with osteopetrosis., Competing Interests: Declaration of competing interest The authors declare that we have no conflicts of interest., (Copyright © 2021 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved.)

The group of sclerosing bone dysplasia's is a clinically and genetically heterogeneous group of rare bone disorders which, according to the latest Nosology and classification of genetic skeletal disorders (2015), can be subdivided in three subgroups; the neonatal osteosclerotic dysplasias, the osteopetroses and related disorders and the other sclerosing bone disorders. Here, we give an overview of the most important radiographic and clinical symptoms, the underlying genetic defect and potential treatment options of the different sclerosing dysplasias included in these subgroups., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Malignant infantile osteopetrosis is a rare genetic disease characterized by increased bone density due to osteoclastic dysfunction. We report on the case of a 3-month-old girl who was referred to our hospital by the ENT department for severe anemia in the context of bilateral choanal atresia. Clinical examination showed failure to thrive, anemia, respiratory distress, bilateral choanal atresia, and chest deformation. The abdomen was soft with large hepatosplenomegaly. We noted a lack of eye tracking, no optical-visual reflexes, and left nerve facial paralysis. The blood count showed normocytic normochromic anemia with severe thrombocytopenia. The infectious work-up and blood smears were negative. The skeleton X-ray showed diffuse bone densification of the skull, long bones, pelvis, vertebrae, and ribs. The facial bone CT confirmed membranous choanal atresia. The molecular biology search for the TCIRG1 gene mutation was not available. The patient had supportive treatment (transfusion, oral steroid, vitamin D, oxygen, nutrition). Bone marrow transplantation was indicated but not available. She died at 6 months in a context of severe anemia and bleeding. Malignant infantile osteopetrosis is rare and symptoms are nonspecific. Diagnosis should be considered in young infants presenting refractory anemia, particularly in the context of choanal atresia. Bone marrow transplantation remains the only curative treatment., (Copyright © 2016 Elsevier Masson SAS. All rights reserved.)

Malignant infantile osteopetrosis is a rare congenital disease characterized by a dysfunction of osteoclasts followed by an abnormal bone densification. We report the case of a 5-month-old infant in whom this disease was suspected because of the clinical (hepatosplenomegaly, gingival hypertrophy), hematological (pancytopenia and hypocalcemia), and radiological criteria (abnormal bone density, periosteal reaction). The genetic investigation confirmed the diagnosis. Compound heterozygous mutations in the CLCN7 gene were identified, including an as yet undescribed mutation. The second mutation had already been described as being responsible for severe and irreversible neurological damage in patients with osteopetrosis. Since this patient presented severely delayed development, he was not eligible for bone marrow transplantation., (Copyright © 2015 Elsevier Masson SAS. All rights reserved.)

We describe a fetus with severe osteopetrosis diagnosed on post-mortem radiographs following termination of pregnancy at 29 weeks for major brain malformations detected on ultrasound. SNP microarray confirmed loss of heterozygosity in 5% of the genome, consistent with parental consanguinity. Sequencing of the genes known to cause severe recessive osteopetrosis, TCIRG1, CLCN7, OSTM1 and SNX10, was negative. Brain malformations are not typically considered part of the phenotypic spectrum of osteopetrosis. We review the literature, and propose that this may represent a novel autosomal recessive variant of osteopetrosis., (Copyright © 2012 Elsevier Masson SAS. All rights reserved.)

Recently a mutation in the SNX10 gene that belongs to the sorting nexin family was identified as a cause of a new subset of human autosomal recessive osteopetrosis. Here, we identified a novel homozygous mutation (c.46C > T, p.Arg16X) in SNX10, in an Iraqi boy from a consanguineous family with a history of infantile osteopetrosis. The proband exhibited macrocephaly, prominent forehead, proptosis of the eyes, strabismus, splenomegaly and joint hyperlaxity. Bone X-rays showed increased bone density, metaphyseal under-modelling, transverse alternating bands of greater and lesser density in tubular bones, anteriorly notched vertebral bodies and bone-in-bone appearance. Brain atrophy, external hydrocephalus and thin corpus callosum were noted at the brain MRI and CT scan. Blood test results revealed the presence of anaemia and leukopenia. Our findings confirm the role of SNX10 in autosomal recessive osteopetrosis and help to better define the core set of manifestations associated with this new pathological entity., (Copyright © 2012 Elsevier Masson SAS. All rights reserved.)

Sclerosing bone disorders are a diagnostic challenge. However, hereditary sclerosing disorders often have characteristic radiological features that allow their diagnosis. Osteocondensation can result from decreased bone resorption; malignant recessive osteopetroses have been related to mutations in several genes necessary for osteoclast function and also, more recently, to osteoclast differentiation (RANK-L). Albers-Schonberg disease or autosomal-dominant osteopetrosis type II has the characteristic 'sandwich vertebrae' and 'bone within bone' radiological features. It has been related to mutation in chloride channel 7, which is necessary for osteoclast acidification. Osteocondensation can also be related to increased bone formation. Camurati-Engelman dysplasia is a disabilitating disorder with leg pain and weakness, and thickening of the diaphysis of long bones on x ray. It is due to activating mutations in the gene encoding TGF-beta, a growth factor that increases bone formation. Other less common recessive or dominant sclerosing disorders, such as endosteal hyperostosis, sclerostosis, van Buchen disease and high bone mass syndrome, are due to mutations in two genes (LRP5 and SOST) of the Wnt pathway that induce increased osteoblast activity. Recent elucidation of the molecular mechanism responsible for several hereditary diseases with osteocondensation has improved our comprehension of bone remodelling. It has allowed the discovery of new targets for the treatment of postmenopausal osteoporosis, some of which are already being investigated in clinical trials. Molecular mechanism for some hereditary osteocondensation remains to be discovered.

Autosomal dominant osteopetrosis II (ADOII) is a relatively benign disorder caused by a missense mutation in the ClCN7 gene. In this study, we characterize the osteoclasts from patients with ADOII, caused by a G215R mutation, and investigate the effect on osteoclast function in vitro. Osteoclasts from ADOII patients and healthy age- and sex-matched controls, were used to evaluate osteoclastogenesis, cell fusion, acidification, and resorptive activity. ADOII osteoclasts in vivo have increased number and size. However, in vitro we observed no significant changes in the osteoclast formation rate, the morphology, and the expression of markers, such as cathepsin K and tartrate-resistant acid phosphatase. When mature ADOII osteoclasts were investigated on mineralized bone, they degraded the bone material, however only to 10 to 20% of the level in controls. We show by acridine orange, that the reduced chloride transport leads to reduced acidification. We show that the residual activity is sensitive to inhibitors of cathepsins and chloride channels, confirming that resorption is reduced but present. In conclusion, this is the first functional in vitro study of human ADOII osteoclasts. We show normal osteoclastogenesis in ADOII osteoclasts. However, the residual activity of the ClC-7 channel in ADOII osteoclasts does not allow sufficient acidification and thereby resorption.