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Osteopetrosis (marble bone disease) is a family of rare genetic disorders characterized by impaired osteoclast function leading to hyperdense, hypovascular, brittle bone. Typical imaging shows increased bone mass and thickened cortical and trabecular bone. Bones are more prone to fracture and osteomyelitis may develop. When considering dental implant placement in a patient with osteopetrosis, the potential for bony fracture and/or osteomyelitis should be considered along with the decreased likelihood of successful osseointegration because of hypovascularity. This clinical report describes an unusual imaging presentation and successful osseointegration of multiple dental implants supporting an implant-supported fixed mandibular prosthesis with long-term survival.

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.

Osteoporosis (OP) is a common age-related disease characterized by a deterioration of bone mass and structure that predisposes patients to fragility fractures. Pharmaceutical therapies that promote anabolic bone formation in OP patients and OP-induced fracture are needed. We investigated whether a neutralizing antibody against Siglec-15 can simultaneously inhibit bone resorption and stimulate bone formation. We found that the multinucleation of osteoclasts was inhibited in SIGLEC-15 conditional knockout mice and mice undergoing Siglec-15 neutralizing antibody treatment. The secretion of platelet-derived growth factor-BB (PDGF-BB), the number of tartrate-resistant acid phosphatase-positive (TRAP+) mononuclear cells, and bone formation were significantly increased in the SIGLEC-15 conditional knockout mice and antibody-treated mice. The anabolic effect of the Siglec-15 neutralizing antibody on bone formation was blunted in mice with Pdgfb deleted in TRAP+ cells. These findings showed that the anabolic effect of the Siglec-15 neutralizing antibody was mediated by elevating PDGF-BB production of TRAP+ mononuclear cells. To test the therapeutic potential of the Siglec-15 neutralizing antibody, we injected the antibody in an ovariectomy-induced osteoporotic mouse model, which mimics postmenopausal osteoporosis in women, and in two fracture healing models because fracture is the most serious health consequence of osteoporosis. The Siglec-15 neutralizing antibody effectively reduced bone resorption and stimulated bone formation in estrogen deficiency-induced osteoporosis. Of note, the Siglec-15 neutralizing antibody promoted intramembranous and endochondral ossification at the damaged area of cortical bone in fracture healing mouse models. Thus, the Siglec-15 neutralizing antibody shows significant translational potential as a novel therapy for OP and bone fracture.

Osteopetrosis is a hereditary disease with an autosomal recessive or autosomal dominant type of inheritance, caused by a disruption in the functional activity of osteoclasts due to gene mutation. The article systematizes data on etiology, classification, pathomorphology, gene disorders based on the analysis of 38 sources of literature, and deals with the modern approa­ches to the treatment of osteopetrosis. Three types of osteopetrosis with different severity degrees of skeletal disorders and pathological severity are described. The main pathomorphological changes in the structural organization of bone tissue are presented and features of the state of osteoclasts are shown depending on the mutation of genes controlling their functional activity. There are no protocols for the treatment of this pathology, but treatment me­thods based on the use of hematopoietic stem cells are under development. The paper presents with clinical case report of a patient with marble bone disease.

Autosomal recessive osteopetrosis has a variable presentation, most commonly including failure to thrive, hypocalcemia, seizures, hepatosplenomegaly, hydrocephalus, vision or hearing loss, and cytopenias. Multiple symptoms are usually seen at presentation. The variability of presentation often delays diagnosis and subsequent treatment. Here, we present a case of an infant with this condition who initially presented with triventricular hydrocephalus with Chiari I malformation. This alone is not a common presentation of this disease, and we present this case to highlight autosomal recessive osteopetrosis as a potential diagnosis in infants presenting with hydrocephalus and discuss the other associated symptoms, management, and prognosis of this condition. The patient was a full-term infant with a routine newborn period. At 6 months, the infant had macrocephaly and frontal bossing with a bulging fontanelle. She was found to have hydrocephalus with moderate ventriculomegaly involving the third and lateral ventricles with an associated Chiari 1 malformation. The infant was asymptomatic at the time. The infant was promptly referred to neurosurgery and underwent an uncomplicated ventriculoperitoneal shunt placement. Post-operative X-rays showed increased density of the skull with other bone changes suggestive of autosomal recessive osteopetrosis. Subsequent lab work and imaging studies were consistent with this condition. The diagnosis was confirmed by genetic testing, and the patient has undergone treatment with hematopoietic stem cell transplant. Hydrocephalus is a common feature of this condition, typically seen in conjunction with other systemic symptoms and laboratory findings. Our patient had a limited initial presentation of triventricular hydrocephalus with Chiari I malformation and was otherwise clinically asymptomatic. There is limited literature of such a presentation, and we highlight this case to increase awareness, as timely diagnosis of these patients is critical for treatment and future outcomes.

Osteopetrosis refers to a group of genetic skeletal disorders characterized by osteosclerosis and fragile bones. Osteopetrosis can be classified into autosomal dominant, autosomal recessive, or X-linked forms, which might differ in clinical characteristics and disease severity. Autosomal recessive osteopetrosis, also known as malignant osteopetrosis, has an earlier onset, more serious clinical symptoms, and is usually fatal. We encountered a 1-day-old girl who was born full-term via vaginal delivery, which was complicated by meconium-stained amniotic fluid, cephalo-pelvic disproportion, and nuchal cord. Routine neonatal care was provided, in addition to blood tests and chest radiography to screen for sepsis, as well as skull radiography to rule out head injuries. Initial blood tests revealed hypocalcemia, which persisted on follow-up tests the next day. Radiographic examinations revealed diffusely increased bone density and a "space alien" appearance of the skull. Based on radiographic and laboratory findings, the infantile form of osteopetrosis was suspected and genetic testing for identification of the responsible gene. Eventually, a heterozygous mutation of the T cell immune regulator 1, ATPase H+ transporting V0 subunit a3 (TCIRG1) gene (c.292C>T) was identified, making this the first reported case of neonatal-onset malignant osteopetrosis with TCIRG1 mutation in South Korea. Early-onset hypocalcemia is common and usually results from prematurity, fetal growth restriction, maternal diabetes, perinatal asphyxia, and physiologic hypoparathyroidism. However, if hypocalcemia persists, we recommend considering 'infantile of osteopetrosis' as a rare cause of neonatal hypocalcemia and performing radiographic examinations to establish the diagnosis.

Brain abscess formation is extremely rare in patients with osteopetrosis. Herein, we report a case of viridans streptococci brain abscess in an immunocompromised child diagnosed with osteopetrosis. The patient presented with a sudden change in mental status and convulsions. Radiological evaluation revealed a temporal lobe brain abscess, and intravenous antibiotherapy was started immediately. The patient underwent abscess drainage, and laboratory investigation of pus material revealed viridans streptococci.

Introduction: Osteopetrosis is an uncommon skeletal disorder characterized by generalized sclerosis of bones due to defective osteoclast function. A wide variation in clinical severity of the disease has been observed. Radiographic features and genetic testing are commonly used to diagnose the condition. Case Presentation: In the present study, we present a case of an extremely rare, atypical and genetically- undetermined form of Osteopetrosis. Conclusion: This patient had some clinical and radiological features of craniometaphyseal dysplasia along with atypical radiological signs of osteopetrosis.

The purpose of this case report was to describe a cat with generalized bone dysplasia, resembling osteopetrosis and Albers-Schönberg disease in humans. A 1-year-3-month-old, intact male, domestic shorthair cat had a 9-month history of multiple bone fractures without known trauma. Most fractures were treated conservatively and two by osteosynthesis. Bone healing occurred but recurring fractures eventually led to euthanasia. Radiographs, computed tomographic imaging, postmortem analysis and histopathologic examination revealed a generalized increase in bone density and mass with preservation of bone shape, obliteration of the bone marrow cavity and persistence of cartilage and primary trabeculae. Abuse and secondary bone diseases were excluded. History, diagnostic bloodwork, radiographs, computed tomographic imaging and histopathologic examination supported the diagnosis of inherited osteopetrosis and strongly resembled Albers-Schönberg disease in humans. The presence of osteoclasts suggested that the underlying pathology might be found in osteoclast dysfunction, deficient number of osteoclasts, inadequate recruitment of osteoclasts, or other micro environmental changes. In (young) cats that are presented with recurring fractures and the possible suspicion of abuse, inherited osteopetrosis should be considered as a differential diagnosis.

Objective A reappraisal of the available evidence of osteopetrosis in the archaeological record as first step in promoting new approaches to rare diseases in paleopathology. Materials and methods Three different approaches are combined: a survey of the last 50 years of bioarchaeological publications; an online search addressing six of the more widely used search engines; macroscopic and radiographic analyses of the human remains from the Neolithic site of Palata 2 (Italy). Results The combined results of the literature survey and the online search identified six cases of osteopetrosis. The majority of search hits place this disease into differential diagnoses. The investigation of the remains from Palata 2, one of the six cases in literature, indicates a non-specific sclerosis of the cranial vault. Conclusions Of the six cases of osteopetrosis, only two, one of the autosomal-recessive type (ARO) and one of the autosomal-dominant type (ADO), are supported by direct osteoarchaeological evidence. Therefore, inaccurate differential diagnoses generate an inflated number of cases in the paleopathological record. Significance This reappraisal calls for a more informed and evidence-based approach to osteopetrosis and, more generally, to rare diseases in paleopathology. Limitations Lack of specific publications on osteopetrosis; more case studies may be present in “gray literature”. Suggestions for further research Cases of osteopetrosis from archaeological and historical collections as well as medical literature are needed to increase knowledge about this rare disease. More precise differential diagnoses are required, particularly when dealing with rare diseases.

Pycnodysostosis is characterized by short stature, osteosclerosis, acro-osteolysis, increased tendency of fractures, and distinctive dysmorphic features. It is a rare autosomal recessive disease caused by biallelic CTSK mutations. The clinical details of 18 patients from Saudi Arabia were reviewed. Short stature, osteopetrosis, acro-osteolysis, and distinctive facial dysmorphism were documented in all cases. Our results highlight the significant complications associated with this disease. The large anterior fontanelle is one of the cardinal signs of this disease; however, half of our patients had small fontanelles and a quarter had craniosynostosis, which caused optic nerve compression. Sleep apnea was of the major complications in three patients. Bone fracture can be a presenting symptom, and in our patients it mainly occurred after the age of 3 years. Bone marrow suppression was seen in a single patient of our cohort who was misdiagnosed initially with malignant osteopetrosis. In this study, we also describe two novel (c.5G > A [p.Trp2Ter], c.538G > A [p.Gly180Ser]) and two reported (c.244-29 A > G, c.830C > T [p.Ala277Val]) CTSK mutations. Our results indicate that the recurrent intronic variant, c.244-29 A > G is likely to be a founder mutation, as it was found in 78% (14/18 patients) of our cohort belonging to the same tribe.

Early onset familial Paget's disease of bone (EoPDB), familial expansile osteolysis, and expansile skeletal hyperphosphatasia are related disorders caused by insertion mutations in exon 1 of the TNFRSF11A gene, which encodes receptor activator of nuclear factor κB (RANK) protein. To understand the mechanisms underlying these disorders, we developed a mouse model carrying the 75dup27 mutation which causes EoPDB. Mice heterozygous for the mutation (Tnfrsf11a75dup27/- ) developed a PDB-like disorder with focal osteolytic lesions in the hind limbs with increasing age. Treatment of these mice with zoledronic acid completely prevented the development of lesions. Studies in vitro showed that RANK ligand (RANKL)-induced osteoclast formation and signaling was impaired in bone marrow cells from Tnfrsf11a75dup27/- animals, but that osteoclast survival was increased independent of RANKL stimulation. Surprisingly, Tnfrsf11a75dup27/75dup27 homozygotes had osteopetrosis at birth, with complete absence of osteoclasts. Bone marrow cells from these mice failed to form osteoclasts in response to RANKL and macrophage colony-stimulating factor (M-CSF) stimulation. This intriguing study has shown that in heterozygous form, the 75dup27 mutation causes focal osteolytic lesions in vivo reminiscent of the human disorder and extends osteoclast survival independently of RANKL signaling. In homozygous form, however, the mutation causes osteopetrosis due to failure of osteoclast formation and insensitivity to RANKL stimulation. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR)..

Carbonic anhydrase (CA) isoenzyme II deficiency--formerly called the syndrome of osteopetrosis with renal tubular acidosis and cerebral calcification--is an autosomal recessive "inborn error of metabolism" that has disclosed important insight concerning osteoclast function. Nearly 50 cases have been described, predominantly from the Middle East and Mediterranean region. It is discovered late in infancy or early in childhood through developmental delay, short stature, fracture, weakness, cranial nerve compression, dental malocclusion, and/or mental subnormality. Typical radiographic features of osteopetrosis are present, and histopathologic study of the iliac crest reveals unresorbed calcified primary spongiosa. The radiographic findings are unusual, however, in that cerebral calcification appears by early childhood and the osteosclerosis and skeletal modeling defects may gradually resolve by adulthood. Patients are usually not anemic. A hyperchloremic metabolic acidosis, sometimes with hypokalemia, is caused by renal tubular acidosis that may be a proximal, distal, or combined type. Several different mutations within the CA II gene have been identified. There is no established medical therapy, and the long-term outcome remains to be characterized. Prenatal diagnosis has not been reported. Delineation of CA II deficiency establishes an important role in humans for CA II. The pathogenesis of the mental subnormality and cerebral calcification is poorly understood; however, CA II deficiency provides significant insight concerning CA II in renal regulation of acid/base homeostasis and osteoclast-mediated bone resorption.

Pycnodysostosis is a rare autosomal recessive disease caused by a mutation in the cathepsin K enzyme gene, a protease that is expressed primarily in osteoclasts and is responsible for bone matrix degradation. The presentation is usually accompanied by short stature, osteoesclerosis, craniofacial dysmorphia and bone fragility. Some papers provide surgical options for fractures of long bones in this type of patients, but none are presenten in European Caucasian patients. The case presented is of a Spanish Caucasian European male with bilateral femoral fracture treated by endomedular nailing.

The purpose of this series is to highlight a range of rare health conditions. Rare health conditions are those that affect no more and usually fewer than one person in every 2000. Many healthcare assistants and nurses will encounter some of these conditions given the high number of these conditions. This 43rd article will briefly explore two of these conditions, homozygous familial hypercholesterolaemia and osteopetrosis, as well as a range of rare phobias.

Identifying comorbidities in polymyalgia rheumatica/giant cell arteritis (PMR/GCA) is crucial for patients’ outcomes. The present study aimed to evaluate the impact of the inflammatory process and glucocorticoid treatment on aortic arterial stiffness and body composition in PMR/GCA. 77 patients with newly diagnosed PMR/GCA were treated with oral glucocorticoids and followed for 40 weeks. Aortic pulse wave velocity (PWV) was measured at baseline and during the follow-up period and compared to the results of temporal artery biopsy (TAB) and 18F-FDG PET/CT. Body composition was assessed by total body DXA at baseline and the end of the study. Of 77 patients (49 (63.6%) female, mean of age: (71.8 ± 8.0)), 64 (83.1%) had pure PMR, 10 (13.0%) concomitant PMR and GCA, and 3 (3.9%) pure GCA. Compared to baseline values, aortic PWV was initially decreased at week 16 (p = 0.010) and remained lower than baseline at week 28 (p = 0.002) and week 40 (p

Osteopetrosis is a rare hereditary disease that develops as a result of genetic mutations leading to impaired development and function of osteoclasts. There are several forms of osteopetrosis that differ in the type of inheritance (autosomal recessive, autosomal dominant and intermediate) and the severity of symptoms. The main clinical manifestations of the disease are frequent pathological fractures, anemia, thrombocytopenia, infectious complications, compression of the cranial nerves and impaired function. With timely diagnosis and successful hematopoietic stem cell transplantation (HSCT), the prognosis is favorable. In the vast majority of cases, transplantation is performed in the first 10 months of life. The literature describes only 12 patients with osteopetrosis who underwent HSCT over the age of 5 years. The article presents a clinical case of osteopetrosis due to a mutation in the CA2 gene (Chr8: 86389420C> G, p.Y193X) in a 30-year-old patient who underwent THSC at the age of 27.

The crystallites of calcium phosphate (CaP) in bones consist of hydroxyl apatite (HA) and amorphous calcium phosphate (ACP). These nanoscale structures of CaP are sculptured by biological bone formation and resorption processes and are one of the crucial factors that determine the overall strength of the constructs. We used one- and two-dimensional 1H-31P solid-state nuclear magnetic resonance (SSNMR) to investigate the nanoscopic structural changes of CaP. Two quantitative measurables are deduced based on the heterogeneous linewidth of 31P signal and the ratio of ACP to HA, which characterize the mineral crystallinity and the relative proportion of ACP, respectively. We analyzed bones from different murine models of osteopetrosis and osteoporosis and from human samples with osteoporosis and osteoarthritis. It shows that the ACP content increases notably in osteopetrotic bones that are characterized by defective osteoclastic resorption, whereas the overall crystallinity increases in osteoporotic bones that are marked by overactive osteoclastic resorption. Similar pathological characteristics are observed for the sclerotic bones of late-stage osteoarthritis, as compared to those of the osteopetrotic bones. These findings suggest that osteoclast-related bone diseases not only alter the bone density macroscopically but also lead to abnormal formation of CaP crystallites. The quantitative measurement by SSNMR provides a unique perspective on the pathology of bone diseases at the nanoscopic level.

Bone plays an important role in regulating mineral balance in response to physiologic needs. In addition, bone is subject to a continuous remodeling process to maintain healthy bone mass and growth. Metabolic bone diseases are a heterogeneous group of diseases caused by abnormalities of bone mass, mineral structure homeostasis, bone turnover, or bone growth. In pediatrics, several significant advances have been made in recent years in the diagnosis of metabolic bone diseases (e.g., osteogenesis imperfecta, hyperparathyroidism, rickets, renal osteodystrophy, pediatric osteoporosis, and osteopetrosis). Imaging is fundamental in the diagnosis of these pathologies.

Background Dense Bone Islands (DBIs) are anatomic variants defined as radiopaque lesions consisting of hamartomatous cortical bone, often presenting as incidental radiographic findings. DBIs can also be known as idiopathic osteosclerosis, bone whorl, focal periapical osteopetrosis, bone scar and enostosis. We found a paucity of literature for management and reporting of this condition in children. For this reason, the authors describe sixteen cases of children and adolescents with dense bony islands and suggest a pathway for management. Case series Cases presented to the RNENT and Eastman Dental Hospital or private practice, either as chance findings or for diagnosis and treatment planning of undiagnosed radiopaque areas. The individuals were aged between 10 and 17 years; 6 boys and 10 girls. All radiographic reports described DBIs. Diagnoses were confirmed by a Dental and Maxillofacial Radiology Consultant and advised no intervention. In some cases, monitoring was advised. Caution in orthodontic tooth movement was advised for five patients. Conclusion DBIs are common findings that seldom require treatment; however, caution should be exercised when undertaking orthodontic movement in the area of a DBI due to a potential risk of root resorption. Accurate identification and multidisciplinary management are of utmost importance.

The ability to determine the sex of extinct dinosaurs by examining the bones they leave behind would revolutionize our understanding of their paleobiology; however, to date, definitive sex‐specific skeletal traits remain elusive or controversial. Although living dinosaurs (i.e., extant birds) exhibit a sex‐specific tissue called medullary bone that is unique to females, the confident identification of this tissue in non‐avian archosaurs has proven a challenge. Tracing the evolution of medullary bone is complicated by existing variation of medullary bone tissues in living species; hypotheses that medullary bone structure or chemistry varied during its evolution; and a lack of studies aimed at distinguishing medullary bone from other types of endosteal tissues with which it shares microstructural and developmental characteristics, such as pathological tissues. A recent study attempted to capitalize on the molecular signature of medullary bone, which, in living birds, contains specific markers such as the sulfated glycosaminoglycan keratan sulfate, to support the proposed identification of medullary bone of a non‐avian dinosaur specimen (Tyrannosaurus rex MOR 1125). Purported medullary bone samples of MOR 1125 reacted positively to histochemical analyses and the single pathological control tested (avian osteopetrosis) did not, suggesting the presence of keratan sulfate might serve to definitively discriminate these tissues for future studies. To further test these results, we sampled 20 avian bone pathologies of various etiologies (18 species), and several MB samples. Our new data universally support keratan sulfate as a reliable marker of medullary bone in birds. However, we also find that reactivity varies among pathological bone tissues, with reactivity in some pathologies indistinguishable from MB. In the current sample, some pathologies comprised of chondroid bone (often a major constituent of skeletal pathologies and developing fracture calluses in vertebrates) contain keratan sulfate. We note that beyond chemistry, chondroid bone shares many characteristics with medullary bone (fibrous matrix, numerous and large cell lacunae, potential endosteal origin, trabecular architecture) and medullary bone has even been considered by some to be a type of chondroid bone. Our results suggest that the presence of keratan sulfate is not exclusive evidence for MB, but rather must be used as one in a suite of criteria available for identifying medullary bone (and thus gravid females) in non‐avian dinosaur specimens. Future studies should investigate whether there are definite chemical or microstructural differences between medullary bone and reactive chondroid bone that can discriminate these tissues.

Objective Osteopetrosis (OP) is a rare, heritable skeletal disorder that is caused by osteoclast dysfunction, leading to failure of bone resorption and increased bone density. The fragility of such dense bone may result in an increased incidence of fractures. Furthermore, surgery in patients with OP is associated with increased technical difficulty and a higher risk of complications. Case report We report a case of a 20-year-old woman with autosomal dominant OP who developed a subtrochanteric femoral fracture. The fracture was treated by open reduction and internal fixation using a dynamic hip screw. Although technical difficulties were experienced and an intraoperative femoral neck fracture occurred, the surgical outcome was satisfactory. Union of the fractures was visible on radiographs obtained 12 months postoperatively. At 2 years postoperatively, the patient was completely free of any complications resulting from her injury and treatment. Conclusion Open reduction and internal fixation may be an effective option for fractures in patients with OP. Orthopedic surgeons should be aware that the increased density and stiffness of osteopetrotic bone increases the risks of intraoperative technical difficulties, iatrogenic fractures, and postoperative complications.

Osteopetrosis refers to a group of rare hereditary disorders characterized by generalized skeletal densification due to limited bone resorption by osteoclasts. The infantile autosomal recessive form represents the most malignant one with onset early in infancy and life expectancy less than 1-2 years without therapy. Frequently, osteopetrosis is complicated by rickets, a condition called osteopetrorickets. Currently, bone marrow transplantation remains the only treatment option. We present a case of infantile autosomal recessive osteopetrosis complicated by rickets in a 2 and a half-month-old female infant with coexistent congenital cytomegalovirus (CMV) infection, successfully treated by hematopoietic stem cell transplantation (HSCT). Diagnostic procedure and differential diagnosis are discussed along with a short review of the literature. Diagnosis of osteopetrosis requires high clinical suspicion, which is enhanced by radiology and confirmed by bone biopsy and molecular analysis. Our patient has been successfully treated by HSCT and has remained in a good general condition thereafter.

Dysosteosclerosis (DOS) is a distinct form of sclerosing bone disease characterized by platyspondyly and progressive osteosclerosis. DOS is genetically heterogeneous. Three causal genes, SLC29A3, CSF1R, and TNFRSF11A are reported. TNFRSF11A-associated DOS has been identified in two patients; however, TNFRSF11A is also a causal gene for osteopetrosis, autosomal recessive 7 (OP-AR7). Whole-exome sequencing in a patient with sclerosing bone disease identified novel compound heterozygous variants (c.414_427 + 7del, c.1664del) in TNFRSF11A. We examined the impact of the two variants on five splicing isoforms of TNFRSF11A by RT-PCR. We found that c.1664del resulted in elongated proteins (p.S555Cfs*121, etc.), while c.414_427 + 7del generated two aberrant splicing products (p.A139Wfs*19 and p.E132Dfs*19) that lead to nonsense mediated mRNA decay (NMD). In the previous two cases of TNFRSF11A-associated DOS, their mutations produced truncated TNFRSF11A protein isoforms. The mutations in all three cases thus contrast with TNFRSF11A mutations reported in OP-AR7, which does not generated truncated or elongated TNFRSF11A proteins. Thus, we identified the third case of TNFRSF11A-associated DOS and reinforced the genotype-phenotype correlation that aberrant protein-producing TNFRSF11A mutations cause DOS.

Infantile malignant osteopetrosis (IMO) is the most severe form of osteopetrosis (OP), which is a group of rare and hereditary disorders that affect the human skeleton by increasing bone density. One of its main consequences is bone marrow invasion by bone sclerosis, leading to progressive bone marrow failure and aplasia, which predisposes to several infections, including osteomyelitis. It is a disease with 99% mortality by the age of ten and an incidence of 1:500,000 live births. The only available treatment is early bone marrow transplantation. The case report describes a 14-year old male patient, diagnosed with IMO since childhood and admitted to the emergency room of the Albert Sabin Children’s Hospital with right facial edema and local pain that started one month before admission. Acute osteomyelitis of the maxilla was diagnosed based on physical examination and complementary tests. In addition to the current condition, the patient had several complications from his underlying disease. He developed sepsis during hospitalization, used antibiotic therapy, and was discharged after one month for home palliative care.

Aims Osteopetrosis (OP) is a rare hereditary disease that causes reduced bone resorption and increased bone density as a result of osteoclastic function defect. Our aim is to review the difficulties, mid-term follow-up results, and literature encountered during the treatment of OP. Methods This is a retrospective and observational study containing data from nine patients with a mean age of 14.1 years (9 to 25; three female, six male) with OP who were treated in our hospital between April 2008 and October 2018 with 20 surgical procedures due to 17 different fractures. Patient data included age, sex, operating time, length of stay, genetic type of the disease, previous surgery, fractures, complications, and comorbidity. Results The mean follow-up period was 92.5 months (25 to 140). Bony union was observed in all of our patients. Osteomyelitis developed in two patients with femoral shaft fractures, and two patients had peri-implant stress fractures. Conclusion Treatment of fractures in OP patients is difficult, healing is protracted, and the risk of postoperative infection is high. In children and young adults with OP who have open medullary canal and the epiphyses are not closed, fractures can be treated with surgical techniques such as intramedullary titanium elastic nail (TENS) technique or fixation with Kirschner (K)-wire. Cite this article: Bone Joint J 2020;102-B(8):1082–1087.

Allogeneic hematopoietic stem cell transplantation (HSCT) is curative for a variety of nonmalignant disorders including osteopetrosis, bone marrow failures, and immune deficiencies. Haploidentical HSCT is a readily available option in the absence of a matched donor, but engraftment failure and other post-transplant complications are a concern. Post-transplant cyclophosphamide (PT-Cy) regimens are gaining popularity and recent reports show promising results. We report our experience with nine pediatric patients with nonmalignant diseases who were transplanted from a haploidentical donor with PT-Cy. From 2015 to 2019, nine children with nonmalignant diseases underwent haploidentical HSCT with PT-Cy, two as a second transplant and seven as primary grafts after upfront serotherapy and busulfan-based myeloablative conditioning. Patient’s diseases included osteopetrosis (n = 5), congenital amegakaryocytic thrombocytopenia (n = 2), hemophagocytic lymphohistiocytosis (n = 1), and Wiskott Aldrich syndrome (n = 1). Two patients failed to engraft following upfront PT-Cy transplants, one was salvaged with a second PT-Cy transplant, and the other with a CD34+ selected graft. None of the patients suffered from graft-versus-host disease. Three patients died from early posttransplant infectious complications and six patients are alive and well. In conclusion, haploidentical HSCT with PT-Cy is a feasible option for pediatric patients with nonmalignant diseases lacking a matched donor.

Osteopetrosis is a rare skeletal dysplasia resulting from an osteoclast defect leading to increased bone mass and density. Hematopoietic stem cell transplantation can rescue the disease phenotype and prevent complications. However, little is known about the skeletal changes hematopoietic stem cell transplantation induces in patients with this disease. The purpose of this study was to describe the skeletal changes after hematopoietic stem cell transplantation in a retrospective cohort of patients diagnosed with osteopetrosis in one medical center over 13 years. For this purpose, all available epidemiological, hematological, biochemical, and radiographic data were collected and quantitatively analyzed. We found a significant early change in bone metabolism markers coinciding with hematopoietic recovery after stem cell transplantation. Hematopoietic stem cell transplantation induced a later significant improvement in both skeletal mineral distribution and morphology but did not lead to complete radiological normalization. Presumably, changes in bone metabolism, skeletal mineral distribution, and morphology were the result of renewed osteoclast function enabling bone remodeling. We propose that biochemical bone metabolism markers and radiological indices be routinely used to evaluate response to hematopoietic stem cell transplantation in patients with osteopetrosis. © 2020 American Society for Bone and Mineral Research.

Aim We present details of a surgical technique to create an intramedullary canal to allow intramedullary fracture fixation in patients with osteopetrosis. Clinical cases are used to facilitate the description. Background Osteopetrosis is a rare, hereditary condition characterised by hard, brittle, “marble bone;” primarily due to osteoclast dysfunction. Patients are prone to fractures and subsequently nonunions, periprosthetic fractures, and metal-ware failure are commonly seen. Due to the increased bone density, deformity, and obliteration of the medullary cavity, fracture fixation is also technically demanding. Technique Creation of a medullary canal allows the use of intramedullary fixation rather than plate and screws for long-bone fractures. Key factors: A new sharp drill bit should be used for each case as blunt drills are more likely to break. Bone is drilled in a pulsatile fashion, with withdrawal every 2–4 seconds for bone swarf to be removed. Constant cooling of the drill bit with saline to help prevent bone necrosis and drill breakage. Regular exchanging of drill bit sizes to expand the canal. The smaller drills start the canal and are used to direct progress. Sequential expansion during canal creation is preferred. Regular use of orthogonal radiographs to ensure correct canal positioning and prevent perforation. Conclusion The creation of an intramedullary canal allows intramedullary fracture fixation. In our experience, this technique gives the orthopaedic surgeon a safe and effective method for treating long-bone fractures in patients with osteopetrosis. Clinical relevance Fractures and nonunions in patients with osteopetrosis are difficult to manage; and by detailing this technique, a further option is now available for surgeons when deciding upon fixation method. How to cite this article Kent J, Ferguson D. Intramedullary Canal-creation Technique for Patients with Osteopetrosis. Strategies Trauma Limb Reconstr 2019;14(3):155–162.

Osteopetrosis is a severe and frequently fatal condition characterized by the formation of thick, dense bone, with a concomitant loss of bone marrow spaces secondary to defective osteoclast function or development. Clinical symptoms include pancytopenia, hepatosplenomegaly, fractures, cranial nerve impingement, and increased cranial pressure, among others. The condition requires rapid diagnosis and clinical intervention, as hematopoietic stem cell transplantation performed early in life can be curative in the majority of cases and can prevent the irreversible neurological impairment associated with the disease. We report a six-month-old male with osteopetrosis where bone marrow examination and molecular studies allowed a definitive diagnosis. Microscopic examination of a bone marrow biopsy demonstrated increased bone formation at various stages of ossification, decreased marrow spaces, and increased osteoclasts rimming the bone. Next-generation sequencing (NGS) demonstrated that the patient was homozygous for mutations in the TCIRG1 gene, which encodes an osteoclast vacuolar proton pump and is the most common mutation associated with the autosomal recessive or infantile malignant form of osteopetrosis. The patient underwent a cord blood stem cell transplant, but unfortunately expired four months after diagnosis. This case highlights the importance of bone marrow biopsy evaluation as part of the integrated approach to diagnosing osteopetrosis.

The prototype fowl glioma-inducing virus (FGVp) causes fowl glioma and cerebellar hypoplasia in chickens. In this study, we investigated whether a strain of avian leukosis virus (ALV), associated w...

Osteopetrosis is a disease of osteoclasts that results in failure of bone remodeling. Despite the sclerotic radiographic appearance of the thickened cortices and its material hardness, osteopetrotic bone is weak and prone to fracture by minor trauma. We report a case of a subtrochanteric fracture in an osteopetrotic patient, with further pseudoarthrosis and infection. Several surgical procedures were required, with further complications. The outcome of each procedure and the final result are also described.

Mice lacking either colony-stimulating factor-1 (CSF-1) or its receptor, CSF-1R, display osteopetrosis. Accordingly, genetic deletion or pharmacological blockade of CSF-1 prevents the bone loss associated with estrogen deficiency. However, the role of CSF-1R in osteoporosis models of type-1 diabetes (T1D) and ovariectomy (OVX) has not been examined. Thus, we evaluated whether CSF-1R blockade would relieve the bone loss in a model of primary osteoporosis (female mice with OVX) and a model of secondary osteoporosis (female with T1D) using micro-computed tomography. Female ICR mice at 10 weeks underwent OVX or received five daily administrations of streptozotocin (ip, 50 mg/kg) to induce T1D. Four weeks after OVX and 14 weeks after first injection of streptozotocin, mice received an anti-CSF-1R (2G2) antibody (10 mg/kg, ip; once/week for 6 weeks) or vehicle. At the last day of antibody administration, mice were sacrificed and femur and tibia were harvested for micro-computed tomography analysis. Mice with OVX had a significant loss of trabecular bone at the distal femoral and proximal tibial metaphysis. Chronic treatment with anti-CSF-1R significantly reversed the trabecular bone loss at these anatomical sites. Streptozotocin-induced T1D resulted in significant loss of trabecular bone at the femoral neck and cortical bone at the femoral mid-diaphysis. Chronic treatment with anti-CSF-1R antibody significantly reversed the bone loss observed in mice with T1D. Our results demonstrate that blockade of CSF-1R signaling reverses bone loss in two different mouse models of osteoporosis.

Supplemental Digital Content is available in the text., Wiskott-Aldrich syndrome (WAS) and osteopetrosis are 2 different, rare hereditary diseases. Here we report clinical and molecular genetics investigations on an infant patient with persistent thrombocytopenia and prolonged fever. He was clinical diagnosed as osteopetrosis according to clinical presentation, radiologic skeletal features, and bone biopsy results. Gene sequencing demonstrated a de novo homozygous mutation in 5′-untranslated region of TNFRSF11A, c.−45A>G, which is relating to osteopetrosis. Meanwhile, a hemizygous transition mutation in WAS gene, c.400G>A diagnosed the infant with WAS. This is the first clinical report for the diagnosis of osteopetrosis coinheritance with WAS in a single patient.

Osteopetrosis (OP) is a group of rare genetic bone disorders. Osteoclast-poor form of osteopetrosis is much rarer in humans and represents a small percentage of the total cases of autosomal recessive osteopetrosis presenting with impaired bone remodeling due to defective osteoclastic activity and is characterized by distinctive increase in bone density and high bone fragility. Reduction in marrow spaces with decreased vasculature to the bone owing to increased bone mass makes the bones vulnerable for varied infections resulting in osteomyelitis. This case report discusses challenges in management of recalcitrant osteomyelitis of mandible developed as a complication in an 8-year-old girl child identified with rare, dual heterozygous mutations in RANKL (TNFSF11) gene and COL5A1 gene with uncertain significance responsible for osteoclast-poor osteopetrosis and Classic Ehlers-Danlos, respectively. How to cite this article Sharma A, Ingole SN, Deshpande MD, et al. A Rare Case of Osteoclast-poor Osteopetrosis (RANKL Mutation) with Recurrent Osteomyelitis of Mandible: A Case Report. Int J Clin Pediatr Dent 2020;13(6):717–721.

Aim This is a case report of a 16-year-old girl visiting MR Ambedkar Dental College and Hospital (Department of Pedodontics and Preventive Dentistry) for dental treatment. Background Osteopetrosis acroosteolytica or Toulouse-Lautrec syndrome or pyknodysostosis is a rare autosomal recessive bone dysplasia, characterized by osteosclerosis, and short stature. Montanari described a patient with an unusual variation of achondroplasia, which in retrospect was the first case of pyknodysostosis to be reported.1 Case description A 16-year-old girl reported to the Department of Pediatric and Preventive Dentistry with a chief complaint of pain in the lower left back region of the jaw since past 2 weeks. Conclusion Pyknodysostosis is a rare condition that is diagnosed basically on its clinical and radiographic features. Clinical significance It is important to recognize these features so that correct diagnosis can be made. This allows the treatment and prevention of future complications and ensures a better quality of life to the patient. How to cite this article Jawa A, Setty JV, Vijayshankar LV, et al. Pyknodysostosis: Report of a Rare Case and its Dental Management. Int J Clin Pediatr Dent 2020;13(2):192–195.

Osteopetrosis is a disorder characterized by high bone density, hepatosplenomegaly, visual and hearing loss, and anemia. Pycnodysostosis presents with short stature, acroosteolysis, and dense bones. We, hereby, present here a family with autosomal dominant osteopetrosis and also children with recessive osteopetrosis and pycnodysostosis. The molecular confirmation was done in 3 cases. Genetic heterogeneity in clinical presentation is discussed here. Further studies will help in identifying epigenetic alterations and population-specific variants and also developing targeted therapies.

Osteopetrosis is a genetically heterogenous, fatal bone disorder characterized by increased bone density. Globally, various genetic causes are reported for osteopetrosis with all forms of inheritance patterns. A precise molecular diagnosis is necessary for prognosis and for prescribing treatment paradigms in osteopetrosis. Here we report on thirteen individuals diagnosed with infantile malignant osteopetrosis coming from ten unrelated Pakistani families; nine of whom are consanguineous. We performed whole exome sequencing and Sanger sequencing in all families and identified homozygous variants in genes previously reported for autosomal recessive inheritance of osteopetrosis. All the identified variants are expected to affect the stability or length of gene products except one nonsynonymous missense variant. TCIRG1 was found as a candidate causal gene in majority of the families. We report six novel variants; four in TCIRG1 and one each in CLCN7 and OSTM1. Our combined findings will be helpful in molecular diagnosis and genetic counselling of patients with osteopetrosis particularly in populations with high consanguinity.

Osteopetrosis is a group of rare inherited skeletal disorders characterized by a marked increase in bone density due to deficient bone resorption. Pathogenic variants in several genes involved in osteoclast differentiation and/or function have been reported to cause osteopetrosis. Solute carrier family 4 member 2 (SLC4A2, encoding anion exchanger 2) plays an important role in osteoclast differentiation and function by exchange of Cl- with HCO3 - . Bi-allelic Slc4a2 loss-of-function mutations in mice and cattle lead to osteopetrosis with osteoclast deficiency; however, pathogenic SLC4A2 variants in humans have not been reported. In this study, we describe a patient with autosomal recessive osteopetrosis due to bi-allelic pathogenic variants in SLC4A2. We identified novel compound heterozygous variants in SLC4A2 (NM_003040.4: c.556G>A [p.A186T] and c.1658T>C [p.V553A]) by exome sequencing. The measurement of intracellular Cl- showed that the variants decrease the anion exchange activity of SLC4A2. The impact of the variants on osteoclast differentiation was assessed by a gene knockout-rescue system using a mouse macrophage cell line, RAW 264.7. The Slc4a2-knockout cells show impaired osteoclastogenesis, which was rescued by the wild-type SLC4A2, but not by the mutant SLC4A2s. Immunofluorescence and pit assay revealed that the mutant SLC4A2s leads to abnormal podosome belt formation with impaired bone absorption. This is the first report on an individual affected by SLC4A2-associated osteopetrosis (osteopetrosis, Ikegawa type). With functional studies, we prove that the variants lead to SLC4A2 dysfunction, which altogether supports importance of SLC4A2 in human osteoclast differentiation. This article is protected by copyright. All rights reserved.

Objective In this review, we focus on the recent progress of circular ribonucleic acids (circRNAs)-related molecular mechanisms in the processes of osteogenesis and osteoclastogenesis, and explore their roles in the development of bone-remodeling disorders. Background The well-coupled bone-formation and bone-resorption processes are vital in bone remodeling. Once the balance is disrupted, bone-remodeling disorders (e.g., osteoporosis and osteopetrosis) occur, severely affecting patients' quality of life. CircRNAs, the newly discovered members of the non-coding RNA family, have been reported to act as key checkpoints of various signaling pathways that influence osteoblasts and osteoclasts functions, thus regulating the physiological and pathological processes of bone homeostasis. Methods Three English and three Chinese databases [i.e., PubMed, Embase, MEDLINE (via Ovid), Chinese Biomedical Literature, China National Knowledge Infrastructure, and VIP databases] were searched to June 2021 without language restrictions. Studies exploring the roles of circRNAs in key bone remodeling mediators, such as Smad-dependent bone morphogenetic protein (BMP)/transforming growth factor beta (TGF-β), Wnts, runt-related transcription factor (RUNX), forkhead boxes (FOXs), colony-stimulating factor 1 (CSF-1), receptor activator of nuclear factor kappa B ligand (RANKL)/osteoprotegerin (OPG), and circRNA-related bone-remodeling disorders, were included. Conclusions Many circRNAs have been shown to promote osteogenesis and facilitate osteoclast differentiation via diverse mechanisms, and thus modulate the process of bone homeostasis. The imbalance or impairment of these two parts causes diseases, such as osteoporosis, and osteonecrosis of the femoral head, which are also closely correlated to the aberrant presence of circRNAs. Current evidence provides us with promising diagnosis and treatment methods for some bone homeostasis disorders.

Dual-energy X-ray absorptiometry (DXA) is underutilized to measure bone mineral density (BMD) and evaluate fracture risk. We present an automated tool to identify fractures, predict BMD, and evaluate fracture risk using plain radiographs. The tool performance is evaluated on 5164 and 18175 patients with pelvis/lumbar spine radiographs and Hologic DXA. The model is well calibrated with minimal bias in the hip (slope = 0.982, calibration-in-the-large = −0.003) and the lumbar spine BMD (slope = 0.978, calibration-in-the-large = 0.003). The area under the precision-recall curve and accuracy are 0.89 and 91.7% for hip osteoporosis, 0.89 and 86.2% for spine osteoporosis, 0.83 and 95.0% for high 10-year major fracture risk, and 0.96 and 90.0% for high hip fracture risk. The tool classifies 5206 (84.8%) patients with 95% positive or negative predictive value for osteoporosis, compared to 3008 DXA conducted at the same study period. This automated tool may help identify high-risk patients for osteoporosis., Dual-energy X-ray absorptiometry and the Fracture Risk Assessment Tool are recommended tools for osteoporotic fracture risk evaluation, but are underutilized. Here, the authors present an opportunistic tool to identify fractures, predict bone mineral density and evaluate fracture risk using plain pelvis and lumbar spine radiographs.

International audience; The purpose of this multicentric study was to evaluate the prevalence and causes of Elevated Bone Mass (EBM) in patients who underwent DXA scanning over a 10-year period. The prevalence of EBM was 1 in 100. The main causes of EBM were degenerative spine disorders and renal osteodystrophy. Introduction Reports of elevated bone mass (EBM) on routine dual energy X-Ray absorptiometry (DXA) scanning are not infrequent. However, epidemiological studies of EBM are few and definition thresholds are variable. The purpose of this French multicentric study was to evaluate the prevalence and causes of EBM in adult patients who underwent DXA scanning over a 10-year period. Methods This multicentric, retrospective study was conducted in six French regional bone centres. DXA databases were initially searched for individuals with a bone mineral density (BMD) Z-score >= +4 at any site in the lumbar spine or hip from April 1st, 2008 to April 30st, 2018. Results In all, 72,225 patients with at least one DXA scan were identified. Of these, 909 (322 men and 587 women) had a Z-score >= + 4, i.e. a prevalence of 1.26% [1.18-1.34%]. The DXA scan reports and imagery and medical records of the 909 EBM patients were reviewed and 936 causes were found. In 42 patients (4%), no cause could be determined due to unavailability of data. Artefactual causes of EBM were found in 752 patients (80%), in whom the predominant cause was degenerative disease of the spine (613 patients, 65%). Acquired causes of focal EBM-including Paget's disease (n = 7)-were found in 12 patients (1%), and acquired causes of generalized EBM-including renal osteodystrophy (n = 32), haematological disorders (n = 20) and hypoparathyroidism (n = 15)-in 84 patients (9%). Other causes were rare hereditary diseases and unknown EBM in 19 (2%) and 27 (3%) cases respectively. Conclusions The prevalence of EBM was approximately 1 in 100. These findings suggest that degenerative disease of the spine is the main cause of EBM, but that acquired or hereditary diseases are also causal factors.

Background Osteopetrosis is characterized by increased bone density and bone marrow cavity stenosis due to a decrease in the number of osteoclasts or the dysfunction of their differentiation and absorption properties usually caused by biallelic variants of the TCIRG1 and CLCN7 genes. Methods In this study, we describe five Chinese children who presented with anemia, thrombocytopenia, hepatosplenomegaly, repeated infections, and increased bone density. Whole‐exome sequencing identified five compound heterozygous variants of the CLCN7 and TCIRG1 genes in these patients. Results Patient 1 had a novel variant c.1555C>T (p.L519F) and a previously reported pathogenic variant c.2299C>T (p.R767W) in CLCN7. Patient 2 harbored a novel missense variant (c.1025T>C; p.L342P) and a novel splicing variant (c.286‐9G>A) in CLCN7. Patients 3A and 3B from one family displayed the same compound heterozygous TCIRG1 variant, including a novel frameshift variant (c.1370del; p.T457Tfs*71) and a novel splicing variant (c.1554+2T>C). In Patient 4, two novel variants were identified in the TCIRG1 gene: c.676G>T; p.E226* and c.1191del; p.P398Sfs*5. Patient 5 harbored two known pathogenic variants, c.909C>A (p.Y303*) and c.2008C>T (p.R670*), in TCIRG1. Analysis of the products obtained from the reverse transcription‐polymerase chain reaction revealed that the c.286‐9G>A variant in CLCN7 of patient 2 leads to intron 3 retention, resulting in the formation of a premature termination codon (p.E95Vfs*8). These five patients were eventually diagnosed with autosomal recessive osteopetrosis, and the three children with TCIRG1 variants received hematopoietic stem cell transplantation. Conclusions Our results expand the spectrum of variation of genes related to osteopetrosis and deepen the understanding of the relationship between the genotype and clinical characteristics of osteopetrosis., Biallelic variants in TCIRG1 and CLCN7 are responsible for Chinese ARO patients. Seven novel variants in TCIRG1 and CLCN7 were identified in Chinese ARO patients. The novel variants c.286‐9G>A in CLCN7 leads to intron 3 retention.

Romosozumab, a humanized monoclonal antibody specific for sclerostin (SOST), has been approved for treatment of postmenopausal women with osteoporosis at a high risk for fracture. Previous work in sclerostin global knockout (Sost−/−) mice indicated alterations in immune cell development in the bone marrow (BM), which could be a possible side effect in romosozumab-treated patients. Here, we examined the effects of short-term sclerostin depletion in the BM on hematopoiesis in young mice receiving sclerostin antibody (Scl-Ab) treatment for 6 weeks, and the effects of long-term Sost deficiency on wild-type (WT) long-term hematopoietic stem cells transplanted into older cohorts of Sost−/− mice. Our analyses revealed an increased frequency of granulocytes in the BM of Scl-Ab-treated mice and WT→Sost−/− chimeras, indicating myeloid-biased differentiation in Sost-deficient BM microenvironments. This myeloid bias extended to extramedullary hematopoiesis in the spleen and was correlated with an increase in inflammatory cytokines TNFα, IL-1α, and MCP-1 in Sost−/− BM serum. Additionally, we observed alterations in erythrocyte differentiation in the BM and spleen of Sost−/− mice. Taken together, our current study indicates novel roles for Sost in the regulation of myelopoiesis and control of inflammation in the BM.

In 2019, the Nosology Committee of the International Skeletal Dysplasia Society provided an updated version of the Nosology and Classification of Genetic Skeletal Disorders. This is a reference list of recognized diseases in humans and their causal genes published to help clinician diagnosis and scientific research advances. Complementary to mammalian models, zebrafish has emerged as an interesting species to evaluate chemical treatments against these human skeletal disorders. Due to its versatility and the low cost of experiments, more than 80 models are currently available. In this article, we review the state-of-art of this “aquarium to bedside” approach describing the models according to the list provided by the Nosology Committee. With this, we intend to stimulate research in the appropriate direction to efficiently meet the actual needs of clinicians under the scope of the Nosology Committee.