Maladie de Paget

Paget's disease is a frequent disorder, characterized by an accelerated bone remodelling. Initial focal bone resorption and the subsequent increased bone formation may mimic several bone disorders, in particular those of neoplastic origin such as the “ivory vertebrae”. In the vast majority of cases, Paget's disease can be diagnosed radiologically, on the basis of typical spectrum of changes, combined changes in bone shape (hyperplasia and enlargement, plastic deformations), in bone density (initial osteolysis, and subsequent osteosclerosis) and in bone structure: a typical thickening with increased porosity of the cortical bone, combined with hypertrophy of the trabecular bone, resulting in the so-called “cortico-trabecular dedifferenciation”. The characteristic distribution of these changes (which may involve one or several bones, either partially or totally, but never the whole skeleton) is an additional hallmark of Paget's disease. In case of uncertainty, MRI is the most appropriate complementary investigation to confirm the diagnosis by demonstrating the characteristic pagetic bone content: persistence of an almost normal fatty marrow signal, intricated with focal signal changes due to hyperostosis (increased mineral bone mass) and with limited amounts of fibro-vascular tissue. Finally, MRI is the preferential tool for early detection of the most fearsome complication of Paget's disease: the malignant transformation that induces the development of abnormal tissue, both inside and around the pagetic bone.