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Bone Diseases: Genetic |
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Osteogenesis imperfecta (Brittle bone disease) This is an autosomal dominate type I collagen defect. Bones are excessively fragile and slight trauma can cause multiple fractures in these patients. Rapid but distorted healing is characteristic. This condition is associated with blue sclera, deafness and dentinogenesis imperfecta. Jaw fracture is not particularly likely, but care must be taken during dental extraction.
Osteopetrosis (Marble bone disease) This condition is characterised by an increasing bone density and brittleness, and a reduction in blood supply. It manifests with bone pain, fracture and compression neuropathies and increased susceptibility to infection (i.e. osteomyelitis) , which is difficult to treat. Medullary spaces are reduced and extramedullary haemopoises is liver and spleen is seen. Despite this anaemia can complicate severe disease. Frontal bossing and hypertelorism are common facial characteristics.
Achondroplasia (Genetic dwarfism) This is an inherited defect in cartilaginous bone formation, usually autosomal dominant. The essential effect is failure of normal cartilage proliferation in the epiphyses and bas of skull. Skull bossing and a protrusive mandible may be a facial characteristic of this disorder. Malocclusion may need correction.
Cleidocranial dysostosis An inherited autosomal dominant defect of membranous bone formation. Skull and clavicles are affected. Partial or complete absence of clavicles allows the patient to bring the shoulders together in front of the chest. Multiple unerupted teeth with retention of the deciduous dentition is characteristic.
Cherubism An inherited autosomal dominant trait, predominantly affecting boys. Symmetrical swellings in the angles of the mandible, and the maxillae is affected in severe cases. These appears around the age of 2—4 years and cause fullness of the cheeks. Growth is rapid for a few years, but slows down until puberty is reached. There is then slow regression until normal facial appearance is restored. Histologically, the lesions consist of multinucleated giant cells and resemble giant cell granulomas of hyperparathyroidism.
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