Osteolytic form of Paget's disease. Differential diagnosis and pathogenesis

Of fourteen patients with Paget's disease for whom adequate roentgenograms and pathological material were available, 6 had lesions showing significant or predominant osteolysis. Based on a study of these six patients and a review of the literature, the following mechanisms were identified as causes of the socalled osteolytic type of the disease: (1) an 'early' destructive Paget's lesion; (2) 'advanced' Paget's disease with secondary degenerative changes; (3) 'seeding' of an independent osteolytic lesion, particularly tumor in preexisting Paget's disease; (4) sarcomatous transformation; and (5) immobilization after fracture. An osteolytic lesion in a patient without other bone disease may be due to Paget's disease, while an associated lytic lesion may be the result of a variety of conditions. Accurate pathological diagnosis is essential.