Of fourteen patients with Paget's disease for whom adequate
roentgenograms and pathological material were available, six 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 so-called 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 pre-existing 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.