Cases reported "Osteopetrosis"

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1/30. Locus heterogeneity of autosomal dominant osteopetrosis (ADO).

    Autosomal dominant osteopetrosis (ADO), is a heritable disorder that results from a failure of osteoclast-mediated bone resorption. The etiology of the disorder is unknown. A previous linkage study of one Danish family mapped an ADO locus to chromosome 1p21. We have studied two families from indiana with ADO. The present study sought to determine if the ADO gene in these families was also linked to chromosome 1p21. We used six microsatellite repeat markers, which demonstrated linkage to the 1p21 ADO locus in the Danish study, to perform linkage analysis in the new kindreds. Multipoint analysis excluded linkage of ADO to chromosome 1p21 (logarithm of the odds score < -7.00) in both families. In addition, no haplotype segregated with the disorder in either family. In summary, the present investigation ruled out linkage of ADO to chromosome 1p21 in two families from indiana. Our results demonstrate that there is locus heterogeneity of this disorder; therefore, mutations in at least two different genes can give rise to the ADO phenotype.
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2/30. Mechanisms of osteoclast dysfunction in human osteopetrosis: abnormal osteoclastogenesis and lack of osteoclast-specific adhesion structures.

    osteoclasts from a patient affected by osteopetrosis were examined in vivo and in vitro. Iliac crest biopsy revealed an osteosclerotic pattern, with prominent numbers of osteoclasts noted for hypernuclearity and incomplete adherence to the bone surface. A population comprising tartrate-resistant acid phosphatase (TRAP)-positive, multinucleated and mononuclear cells, and alkaline phosphatase-positive stromal fibroblasts was obtained in vitro from bone marrow. Mononuclear TRAP-positive precursors spontaneously fused in culture to form giant osteoclast-like cells. These cells expressed the osteoclast marker MMP-9 and calcitonin receptor, and lacked the macrophage marker, Fc receptor. Expression and distribution of c-src, c-fms, and CD68, and response to steroid hormones relevant to osteoclast differentiation and function were apparently normal, whereas cell retraction in response to calcitonin was impaired. TRAP-positive multinucleated cells did not form osteoclast-specific adhesion structures (clear zone, podosomes, or actin rings). bone resorption rate was severely reduced in vitro. focal adhesions and stress fibers were observed en lieu of podosomes and actin rings. Adhesion structures contained low levels of immunoreactive vitronectin receptor, most of this integrin being retained in cytoplasmic vesicles. These data provide the first characterization of abnormal differentiation and function of human osteopetrotic osteoclast-like cells.
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3/30. Study of the nonresorptive phenotype of osteoclast-like cells from patients with malignant osteopetrosis: a new approach to investigating pathogenesis.

    osteopetrosis manifests as failure of osteoclastic bone resorption. The cause of the disease lies either in the hematopoietic lineage or in the bone marrow stromal microenvironment. It has not been possible to define the cell type involved in the various forms of the human disease because of the inability to form human osteoclasts in vitro. Using the recently described method for generating human osteoclasts from peripheral blood in coculture with rat osteoblastic UMR 106 cells, we demonstrate that a defect lies in the mature osteoclast-like cells in four cases of this disease. Control and osteopetrotic cocultures generated large numbers of osteoclast-like cells (calcitonin and vitronectin receptor positive, and F-actin ring-positive cells) with similar morphology. bone resorption did not occur in three of the four osteopetrotic cultures. In case 1, in which bone resorption was identified, the area of resorption was negligible compared with the number of osteoclast-like cells in the culture and was detected only by scanning electron microscopy. In contrast, up to 20% of the bone surface in controls was resorbed. The normal and osteopetrotic osteoclast-like cells had a similar phenotype except that two of the osteopetrotic cases did not express CD44 and two expressed CD44 weakly, whereas CD44 was strongly expressed in the controls. This study shows that it is possible to reproduce in vitro the pathological features of human osteopetrosis, and the assay provides a means of acquiring a greater understanding of the pathogenesis of human osteopetrosis.
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keywords = resorption
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4/30. Long-term follow-up of two children with a variant of mild autosomal recessive osteopetrosis undergoing bone marrow transplantation.

    Malignant autosomal recessive (AR) osteopetrosis represents an absolute indication for bone marrow transplantation (BMT). Over the last 15 years, almost 100 BMTs for osteopetrosis have been reported. The median age at transplant of most patients is 4 months. Very few cases of mild AR osteopetrosis have been described. Here, we report the good outcome of two cases of mild AR osteopetrosis with a follow-up of 5 and 6 years, respectively, after an HLA-identical sibling transplant undergone at 5 and 12 years of age, respectively. At the time of BMT, severe visual impairment was present in both children. Bone biopsy demonstrated hypermineralization with virtual obliteration of the medullary spaces, rare microfoci of hematopoiesis and marked deficiency in osteoclastic activity. Successful engraftment was complicated by hypercalcemia, controlled by a combination of bisphosphonate, phosphate infusions, vigorous hydration and calcitonin. Following BMT, radiological and histological findings showed extensive bone resorption with marked augmentation of the osteoclasts in normalized marrow. No improvement was observed in visual acuity, despite complete remodeling of skeletal abnormalities. We conclude that allogeneic BMT is the only chance of curing mild AR osteopetrosis.
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keywords = resorption
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5/30. Higher osteoclastic demineralization and highly mineralized cement lines with osteocalcin deposition in a mandibular cortical bone of autosomal dominant osteopetrosis type II: ultrastructural and undecalcified histological investigations.

    In this study we report on histological and ultrastructural investigations of the mandibular cortical bone in a case of autosomal dominant osteopetrosis type II complicated by mandibular osteomyelitis. Histologically, there was a marked increase in the number and size of osteoclasts on the inner bone surface. An undecalcified preparation showed a pair of deeply stained (highly demineralized) and stain-phobic (highly mineralized) layers on the bone surface just beneath the osteoclasts. The layers were incorporated into the bone matrix during the remodeling process as thickened cement lines. A contact microradiogram of the cortical bone revealed highly mineralized layers at the cement lines, which were closely correlated with immunohistochemical evidence of deposition of osteocalcin at the thickened cement lines. Ultrastructural examination showed that the osteoclasts had a typical clear zone, but they were deficient in ruffled border formation and had numerous lysosomal vacuoles containing dense substances. An electron-dense amorphous material layer was present on the bone surface just beneath the osteoclasts as well as at the cement lines. The layer was partly composed of a short fibrillar material, and it partially revealed the lamellar structure. Consequently, an osteoclastic malfunction might be primarily involved in the process of bone matrix resorption rather than demineralization, resulting in higher demineralization and abnormal material deposition on the bone surface and at the cement lines. Furthermore, evidence of active osteoclastic bone resorption with a brush border formation at the bone involved in the inflammatory lesion in this case suggests that the osteoclastic malfunction is influenced and recovered by a microenvironment such as inflammatory cytokines.
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keywords = resorption
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6/30. Peripheral T-cell lymphoma in a patient with osteopetrosis.

    osteopetrosis is a rare genetic disorder in which the function of osteoclasts is defective, resulting in impaired bone resorption. This disease is usually accompanied by myelosuppression due to decreased marrow space and by osteomyelitis, especially in the submandibular bone. We report the case of a 72-year-old woman with an autosomal dominant form of osteopetrosis who suffered from peripheral T-cell lymphoma. Accurate clinical and pathological diagnoses and staging were difficult due to nonspecific reactive hyperplasia of the lymph nodes, even though we used several scintigraphic techniques and [18F]fluorodeoxyglucose positron emission tomography. We also paid special attention to myelosuppression and exacerbation of osteomyelitis after combination chemotherapy. Severe infectious complications were avoided by early administration of G-CSF for leukocytopenia and by continuous oral administration of antibiotics. The patient achieved complete remission after four courses of chemotherapy and this status has been maintained for 6 months.
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keywords = resorption
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7/30. Malignant infantile osteopetrosis initially presenting with neonatal hypocalcemia: case report.

    Autosomal recessive "malignant" osteopetrosis is a rare congenital disorder relating to bone resorption abnormalities. It is believed to arise due to the failure of osteoclasts to resorb immature bone. This leads to abnormal bone marrow cavity formation and, clinically, to the signs and symptoms of bone marrow failure. Impaired bone remodeling associated with dysregulated activity of osteoclasts for such a condition may typically result in bony narrowing of the cranial nerve foramina, which typically results in cranial nerve (especially optic nerve) compression. Abnormal remodeling of primary woven bone to lamellar bone results in "brittle" bone that is prone to fracture. Thus, fractures, visual impairment, and bone marrow failure are the classical features of this disease. We describe the case of a 23-day-old boy in whom neonatal hypocalcemia was present initially after birth. Malignant infantile osteopetrosis (MIO) was diagnosed for the patient at 4 months of age based on evidence of anemia, thrombocytopenia, leukoerythroblastosis, sclerotic bone, hepatosplenomegaly, and visual deficit from a bony encroachment by the cranial nerve foramina. Although only occasionally reported previously, MIO remains essentially unrecognized by clinicians as a cause of neonatal hypocalcemia, which often results in diagnostic confusion and delay. This is important in the context of curative hemopoietic stem cell transplantation where preservation of sight may depend upon early intervention.
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keywords = resorption
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8/30. Osteoclast morphology in autosomal recessive malignant osteopetrosis due to a TCIRG1 gene mutation.

    Bone biopsies were performed before and 7 weeks after transplantation of HLA-compatible bone marrow from the sister of a 3-month-old male infant with malignant autosomal recessive osteopetrosis due to a mutation in the TCIRG1 (ATP6i) gene. The first biopsy showed broad, immature bony trabeculae and no medullary hematopoiesis. Only few osteoclasts were present and electron microscopy showed absence of ruffled borders. The post transplant biopsy revealed donor osteoclasts with ruffled borders and intracytoplasmic mineral crystals as proof of active bone resorption that had not yet been detectable radiographically. osteopetrosis is a genetically heterogeneous disease. Definition at the dna-level will enable comparison of treatment strategies and prenatal diagnosis. As shown in this patient, the autosomal recessive form caused by a TCIRG1 gene mutation may be amenable to bone marrow transplantation. Activity of donor osteoclasts can be demonstrated morphologically on biopsy, before bone remodeling becomes evident radiologically.
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ranking = 1
keywords = resorption
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9/30. osteopetrosis and Glanzmann's thrombasthenia in a child.

    Autosomal recessive osteopetrosis is a rare, fatal disease characterized by accumulation of excessive bone mass due to defective bone resorption. The pathogenesis of osteopetrosis is controversial. Osteoblast-osteoclast interaction defects, incorrect differentiation of osteoclasts, abnormal contact between osteoclast and extracellular matrix, and abolished signaling are included in this process. Recently, mutations in the gene of the vacuolar proton pump have been described in some cases of recessive osteopetrosis. Glanzmann's thrombasthenia (GT) is a rare hereditary qualitative platelet disorder characterized by a lifelong bleeding tendency due to quantitative and qualitative abnormalities of the platelet integrin alpha(IIb) beta3. Several mutations on either integrin alpha(IIb) [glycoprotein (GP) IIb] or integrin beta(3) (GP IIIa) were reported in GT. We report on a patient with autosomal recessive osteopetrosis concurrently diagnosed with variant type Glanzmann's thrombasthenia. To our knowledge, our patient was the first case reported in the literature in which osteopetrosis and Glanzmann's thrombasthenia were diagnosed together.
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keywords = resorption
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10/30. role of osteoclastic dysfunction in the development of renal bone disease.

    A 47-year-old-man was referred for treatment for end-stage renal failure. He had been diagnosed with type II adult onset osteopetrosis before the deterioration of his renal function. He presented with anaemia, severe hypocalcaemia, secondary hyperparathyroidism and azotaemia. An iliac bone biopsy revealed increased bone volume, disturbed osteoid calcification, active osteoclastic bone resorption and fibrous transformation in the bone marrow space. Incomplete osteoclastic dysfunction strongly suggested hypocalcaemia and secondary hyperparathyroidism, and the osteoclastic bone resorption also indicated secondary hyperparathyroidism, even though bone resorption was potentially suppressed. The present case shows that evidence of the involvement of osteoclastic dysfunction in the development of renal bone disease can be found in bone histology.
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keywords = resorption
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