Paget's Disease of Bone
The distinctive pathologic feature of PD is focal areas of rapid bone remodelling. It is hypothesised that the primary abnormality is increased osteoclast activity, with an increase in the number and size of osteoclasts causing rapid bone resorption. Clinically, this can be seen as lytic areas, especially in long bones or the skull, that progress at approximately 1 cm/year. In response to the increased bone resorption, bone formation is also markedly increased. The newly formed bone is chaotic, lacking the normal lamellar pattern, and is enlarged, sclerotic and weaker than normal bone. Abnormal gene expression has been shown in other cells in PD, including osteoblasts and bone marrow stromal cells, which offers support to the hypothesis that the primary abnormality might lie outside the osteoclast.
Pathology
The distinctive pathologic feature of PD is focal areas of rapid bone remodelling. It is hypothesised that the primary abnormality is increased osteoclast activity, with an increase in the number and size of osteoclasts causing rapid bone resorption. Clinically, this can be seen as lytic areas, especially in long bones or the skull, that progress at approximately 1 cm/year. In response to the increased bone resorption, bone formation is also markedly increased. The newly formed bone is chaotic, lacking the normal lamellar pattern, and is enlarged, sclerotic and weaker than normal bone. Abnormal gene expression has been shown in other cells in PD, including osteoblasts and bone marrow stromal cells, which offers support to the hypothesis that the primary abnormality might lie outside the osteoclast.
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