Effects of hypothalamic leptin gene therapy on osteopetrosis in leptin-deficient mice.

Impaired resorption of cartilage matrix deposited during endochondral ossification is a defining feature of juvenile osteopetrosis. Growing, leptin-deficient ob/ob mice exhibit a mild form of osteopetrosis. However, the extent to which the disease is (1) self-limiting and (2) reversible by leptin treatment is unknown. We addressed the first question by performing histomorphometric analysis of femurs in rapidly growing (2-month-old), slowly growing (4-month-old) and skeletally mature (6-month-old) wild-type (WT) and ob/ob male mice. Absent by 6 months of age in WT mice, cartilage matrix persisted to varying extents in distal femur epiphysis, metaphysis and diaphysis in ob/ob mice, suggesting that the osteopetrotic phenotype is not entirely self-limiting. To address the second question, we employed hypothalamic recombinant adeno-associated virus (rAAV) gene therapy to restore leptin signaling in ob/ob mice. Two-month-old mice were randomized to one of the three groups: (1) untreated control, (2) rAAV-Leptin or (3) control vector rAAV-green fluorescent protein and vectors injected intracerebroventricularly. Seven months later, rAAV-leptin-treated mice exhibited no cartilage in the metaphysis and greatly reduced cartilage in the epiphysis and diaphysis. At the cellular level, the reduction in cartilage was associated with increased bone turnover. These findings (1) support the concept that leptin is important for normal replacement of cartilage by bone, and (2) demonstrate that osteopetrosis in ob/ob mice is bone-compartment-specific and reversible by leptin at skeletal sites capable of undergoing robust bone turnover.

Clinical Characteristics and Treatment of Osteopetrosis Complicated by Osteomyelitis of the Mandible.

Osteopetrosis represents a heterogeneous group of rare, hereditary bone disorders with variable clinical features, and an increase in bone density. Osteomyelitis of the jaws is a significant complication of osteopetrosis. In this article, a reported patient with osteopetrosis complicated by osteomyelitis of the mandible was examined. The patient was treated with intravenous antibiotic therapy, debridement of necrotic bone and hyperbaric oxygen therapy; in addition, the authors attempted to implant the calcium sulfate and vancomycin to reconstruct the bone defect. The patient demonstrated satisfactory healing, and no recurrence of osteomyelitis was observed during the 6-month follow-up period. The treatment of osteopetrosis complicated by osteomyelitis of the mandible is difficult. The treatment of osteopetrosis complicated by osteomyelitis is controversial. The authors recommend the following sequential treatment of osteopetrosis complicated by osteomyelitis of the mandible: systemic antibiotic therapy and hyperbaric oxygen therapy before and after surgery; debridement of the necrotic bone; sufficient periosteal coverage and adequate soft tissue to cover the wound; implantation with calcium sulfate and vancomycin to reconstruct the bone defect as much as possible, which may be helpful in treating the disease.

[Malignant infantile osteopetrosis revealed by choanal atresia: A case report]. / Ostéopétrose maligne infantile révélée par une atrésie des choanes : à propos d'un cas.

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.

Rickets in osteopetrosis--a paradoxical association.

Osteopetrosis is a hereditary bone disease with intense positive balance of body calcium. Infantile variety is often associated with rickets--a paradoxical association. Two siblings with osteopetro rickets are reported in the article. The pathophysiologic mechanism of the paradoxical association has been explained and various management options have been discussed. Both cases were treated with high dose calcitriol and calcium supplements.

Osteopetrorickets: case report.

UNLABELLED: We report the case of a baby girl who presented with rickets at 3 months. At the age of 5 months she was readmitted because of nystagmus and a diagnosis of osteopetrosis was made on the basis of clinical and radiological findings. Rickets is a paradoxical feature of osteopetrosis resulting from inability to maintain a normal calcium-phosphorus balance. In our patient the onset of rickets before other symptoms of osteopetrosis suggests a primary defect. CONCLUSION: It is possible that patients with osteopetrosis and rickets (osteopetrorickets) represent a different mutation like the osteopetrosis mouse, which is the only animal mutation with rickets.

Malignant infantile osteopetrosis: otolaryngological complications and management.

OBJECTIVES: To inform otolaryngologists about upper airway obstruction requiring tracheotomy and other otolaryngological manifestations of malignant infantile osteopetrosis (MIOP) and to discuss pathophysiological features, management, and new treatment strategies in MIOP. DESIGN: Ongoing case series combined with a retrospective chart review. SETTING: International tertiary pediatric hospital. INTERVENTIONS: Patients with MIOP were initially referred for treatment and routine follow-up. Tracheotomy was performed to manage obstructive sleep apnea. Audiograms were also performed at regular intervals. RESULTS: The records of 9 patients were examined. The otolaryngological findings of hearing loss, obstructive sleep apnea (sometimes requiring tracheotomy), otitis media, and chronic osteomyelitis with facial fistulas were identified. CONCLUSIONS: Osteopetrosis is a rare condition caused by a failure of the osteoclast to resorb bone. This results in thickened dense, deformed, and easily fractured bone. As a result, growth failure, anemia, hypoplastic dentition, chronic infections, facial fistulas, blindness, hearing loss, nasal congestion, and upper airway obstruction may occur. The management of otolaryngological problems in a child with osteopetrosis is an important component in comprehensive care. To our knowledge, this study represents the largest case series of MIOP in the otolaryngology literature.

Hypophosphatemia and the development of rickets in osteopetrotic (op/op) mice.

Our previous work has shown that op/op mice hyperabsorb dietary calcium in the vitamin D-deficient state and shunt that calcium into bone. Under these conditions, the op/op mice are hypocalcemic. The purpose of this study was to examine calcium metabolism and bone mineralization in vitamin D-deficient op/op mice. First, the op/op mice and their normal littermates were placed on a vitamin D-deficient, low phosphorus diet to limit bone mineralization. Under these circumstances, op/op mice survived, even when calcium was also removed from the diet. If the diet contained phosphate, op/op mice died from hypocalcemic tetany when calcium was also removed from the diet. Furthermore, serum calcium levels became similar to wild type in the op/op mice administered the vitamin D-deficient, low phosphorus diet, and op/op mice were able to increase serum calcium in response to 1,25-dihydroxyvitamin D3. The op/op mice developed rickets when their serum phosphorus level was too low to support bone mineralization. The op/op mice became hypophosphatemic on regimens in which normal mice were able to maintain normal serum phosphorus levels. It appears that the op/op mouse simply requires a higher dietary calcium and phosphorus level to prevent rickets and hypocalcemic tetany since the bone is not available as a source of these minerals. However, the ability of the op/op mouse to mineralize bone at low serum calcium and phosphorus levels remains unexplained.

Neonatal reductions in osteoclast number and function account for the transient nature of osteopetrosis in the rat mutation microphthalmia blanc (mib).

We have examined the general and skeletal manifestations of osteopetrosis in a new, mild osteopetrotic mutation in the rat, microphalmia blanc (mib). Newborn mutant (mib) rats exhibit the typical skeletal deformities and sclerosis of osteopetrosis at birth, which are reduced significantly during the first postnatal month but don't disappear entirely up to 8 months later. Osteoclast numbers, staining for TRAP and TraATPase, and bone resorption are reduced in mutants during the first 2 postnatal weeks but improve by 1 month. In mutants, serum concentrations of calcium and phosphorus are normal, but 1,25(OH)2 D levels are higher at 1 week than those in normal littermates. Neonatally, mutants exhibit extramedullary hemopoiesis in the spleen. These results are interpreted to mean that the transient perinatal skeletal sclerosis in mib rats is caused by reduced production and function of osteoclasts in this period. The recent description of transient, perinatal osteopetrosis in a child suggests that analyses of the early differences between mild and severe animal mutations might distinguish those children with osteopetrosis who need treatment from those who do not.

Osteopetrosis. Current clinical considerations.

Osteopetrosis is an inherited skeletal condition characterized by increased bone radiodensity. There are three clinical groups: infantile-malignant autosomal recessive, fatal within the first few years of life (in the absence of effective therapy); intermediate autosomal recessive, appears during the first decade of life but does not follow a malignant course; and autosomal dominant, with full-life expectancy but many orthopaedic problems. The infantile variant shows a myelophthisic anemia, granulocytopenia, and thrombocytopenia, and patients eventually die from infection or bleeding or both. Neurologic sequelae include cranial nerve compression (optic nerve, blindness; auditory nerve, deafness; facial nerve, paresis), hydrocephalus, convulsions, and mental retardation. Radiographs show uniform bone density without corticomedulary demarcation, broadened metaphyses, "bone within a bone" or endobone phenomena (tarsals, carpals, phalanges, vertebra, ilium), and thickened growth plates if there is superimposed rickets. Transverse pathologic fractures occur, often followed by massive periosteal bone formation. Computed tomographic scans, magnetic resonance imaging, and bone scans provide specific information. Iliac crest bone biopsy is valuable to quantitate osteoclast and marrow changes by light and electron microscopy. Medical treatments involve high-dose calcitriol to stimulate osteoclast differentiation and bone marrow transplantation to provide monocytic osteoclast precursors. Orthopaedic problems in the intermediate and autosomal dominant forms include increased fractures, coxa vara, long-bone bowing, hip and knee degenerative arthritis, and mandibular and long-bone osteomyelitis. Cranial nerve compression also occurs. Osteotomy, plating, intramedullary rodding, and joint arthroplasty can be done, but are difficult because of bone hardness.

"Osteopetrosis" in the Fairbank Collection.

The "osteopetrosis" section of the Fairbank Collection in the Radiology Museum of the Royal National Orthopaedic Hospital contains radiographs and case notes of twenty-two patients. This material has been reviewed in terms of modern concepts in an attempt to obtain a long-term follow-up and a firm diagnosis in each individual. Nine patients proved to have the classical autosomal dominant form of osteopetrosis, four had the malignant autosomal recessive type, craniometaphyseal dysplasia was present in two kindreds and isolated individuals had pyknodysostosis, atypical craniodiaphyseal dysplasia and craniosclerosis with osteopathia striata. As these conditions differ greatly in their clinical and genetic prognoses, diagnostic categorisation is of practical importance.

Hyperbaric oxygen treatment of mandibular osteomyelitis in osteopetrosis.

A patient was successfully treated with hyperbaric oxygen for chronic osteomyelitis of the mandible associated with osteopetrosis. This mode of therapy appears to have a definite place in the management of such patients. There was no clinical, radiographic, or laboratory evidence that the osteopetrosis was made worse by the hyperbaric oxygen.