Osteopetrosis (marble bone disease)
This condition may be inherited in either an autosomal dominant or an autosomal recessive manner; the recessive type is severe and the dominant type is mild. In the severe form, bone density is increased throughout the skeleton but bones tend to fracture easily. Involvement of the bone marrow leads to a leucoerythroblastic anaemia. There is mental retardation and early death.
In the mild form there may only be X-ray changes, but fractures and infection can occur. The acid phosphatase level is raised.
This rare autosomal recessive condition is due to a deficiency of alkaline phosphatase and pyrophosphatase. It is not known where the primary defect lies, but it may be in the osteoblasts. It varies in severity from unrnineralized bones in utero resulting in death, to rickets in infancy or recurrent fractures in adults.
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