Osteolytic-Expansive Type of Familial Paget's Disease (Osteitis Deformans)

Abstract

Summary In Paget's disease of bone, the diagnosis is usually made readily from x-ray findings, and if needed, from additional laboratory data. Here we present an unusual case of a familial osteitis deformans (Paget's disease) in two brothers whose father died of a Paget sarcoma of the femur with lung metastases. The extraordinary appearance of the x-ray, involving a large, lytic expansive lesion with ground glass appearance, especially in the fibula and radius bilaterally, and the early onset of the disease in the second decade of life, made it necessary to confirm the diagnosis histologically. Fibrous dysplasia and malignant change in the lesion had to be ruled out. The histologic appearance had to be distinguished from fibrous dysplasia and hyperparathyroidism. Microscopically the predominant pattern was one of filigree-like trabeculae of woven bone with a fibrous marrow. The slender trabeculae were o-, u-, and s-shaped as seen in fibrous dysplasia. There was dissecting osteitis as seen in hyperparathyroidism. The following histologic criteria, however, confirmed the diagnosis of osteitis deformans in its active phase: an abundance of osteoclasts and osteoblasts lining the edges of woven bone trabeculae; giant osteoclasts with a bizarre shape and large number of nuclei; various stages of degeneration of osteocytes, including nuclear pyknosis; large vascular channels and round cell infiltration of fibrous marrow; and abundant subperiosteal bone formation with a pumice bone pattern. A typical mosaic pattern was absent in this active phase of the disease. A possible cause of the extensive expansion of this lesion is the relatively low mechanical stress of the fibula, as in the skull of Paget's disease, where we see the same histologic pattern in the form of osteoporosis circumscripta. The familial occurrence also suggests a genetic cause of this morphologic variant of Paget's disease.