​Pathology - Paget Disease of the Bone

​Pathology - Paget Disease of the Bone 
induced by an increase in both osteoblastic and osteoclastic activity, which has been postulated to be induced by a viral infection (possibly paramyxovirus).

Gross: Can occur in one bone (monostotic) or numerous (polyostotic) and tends to involve the skull, pelvis, femur, tibia, and spine.

Microscopic: Several morphologic stages in bone: (1) Osteolytic: large osteoclasts with multiple resorption pits; (2) Osteoclastic osteoblastic: mosaic pattern of lamellar bone demonstrating both bone destruction and bone formation, both osteoclasts and osteoblasts seen; (3) Late osteosclerotic: sclerotic bone with predominance of thick trabeculae, dark mosaic lines evident.

May be asymptomatic or may manifest with bone discomfort, fractures or aberrant bone growth and deformities (increase in hat size or bowing of legs).

Complications include high-output heart failure (increased vascularity leads in numerous arteriovenous shunts), osteosarcoma, hearing loss (due to narrowing of auditory foramen), and long-bone fractures.
Imaging: Mixed thickness and lucency of bone.
Lab findings: Increased serum ALP, normal serum calcium and phosphorus, normal PTH values.

Treatment Bisphosphonates (inhibit osteoclastic activity) for symptomatic illness.