Imaging of Paget disease of bone and its musculoskeletal complications: review.

Objective Paget disease is the second most common bone disease after osteoporosis that affects elderly persons in the United States. We revisit Paget disease of bone and present the gamut of imaging findings associated with this skeletal disorder, both uncomplicated and complicated. Conclusion Paget disease of bone shows a plethora of imaging patterns and variable appearances that are related to the pathologic stage of the disease. Because patients with Paget disease may develop various musculoskeletal complications, recognition of the key imaging features of the condition may allow prospective diagnosis of the disease and its associated musculoskeletal complications and can preclude biopsy. Introduction Paget disease (osteitis deformans) is a chronic skeletal disorder characterized by abnormal and excessive remodeling of bone. The disease was named after Sir James Paget who described the condition in 1877 [1] in a detailed essay recognized in the medical literature as "a lesson in accurate and lucid writing" [2]. Paget disease is estimated to affect approximately 3—4% of individuals older than 40 years [2-4] and is the second most common bone disease after osteoporosis that affects the growing population of older persons in the United States [5]. Abnormal osseous resorption and apposition in Paget disease produce variable clinical and imaging manifestations. Although the disease may be asymptomatic, it can be painful or deforming and associated with various and debilitating musculoskeletal complications [3, 6-8]. Radiologists play a central role in the imaging diagnosis of the process and its multifaceted manifestations. Radiography remains the most inexpensive method to evaluate patients with Paget disease of bone. CT, bone scintigraphy, and MRI have complementary roles in achieving the correct diagnosis of Paget disease and its complications. This article reviews the demographics, basic pathophysiology, natural history, and clinical presentation of Paget disease; describes the imaging appearances of the condition and of its complications; and illustrates many cases of Paget disease of bone, both uncomplicated and complicated. Demographic Profile Descriptive epidemiologic studies have shown that the prevalence (4.6%) of Paget disease is considerably higher in the United Kingdom than in other countries. The disease is also common in Australia, New Zealand, Western Europe, and the United States, although it is rare in Scandinavia, Asia, the Middle East, and Africa [9, 10]. Studies, however, indicate a substantial reduction in the prevalence of Paget disease around the world of approximately 50% [9, 11-15]. For example, in Britain the overall prevalence rate documented in 1994 was 2%, indicating a significant decline in prevalence of 40% over a 20-year period [12]. Another large study in England and Wales estimated that the prevalence of the disorder was 0.3% in subjects over 55 years old [13]. Similarly, data indicate a remarkable 50% decline in the prevalence of the disease in New Zealand over the past two decades [14]. Also, a decline in the prevalence of Paget disease has been realized in some European countries over a 20-year period, reaching an overall rate of 0.3% [15]. Epidemiologic studies show that there is a slight_male predilection in the condition in a proportion of 3:2, with the frequency of Paget disease increasing remarkably in both sexes with advancing age [9, 11—13, 16, 17]. Cause and Pathogenesis The cause of Paget disease remains largely unknown even more than one century after its original description. The discovery of characteristic intranuclear and intracytoplasmic inclusion bodies resembling nucleocapsids of the paramyxo-virus family of RNA viruses in the osteoclasts of pagetic bone triggered the theory of a slow virus infection [11, 18-20]. Indeed, nuclear inclusions are considered a striking feature of pagetic osteoclasts because they are not present in other bone marrow cells and are consistently found in patients with Paget disease [20]. In addition, osteoclasts in pagetic lesions are increased in both number and size and are.