Osteitis deformans (Pagets disease)

Pathogenesis

• Chronic localized areas of bone destruction with concurrent exuberant bone repair
• Primary process: Localized osteolysis due to enhanced number and activity of osteoclasts
• Continued reparative osteogenesis by osteoblasts
• Greater blood supply and arterio-venous shunting in bone can lead to local warmth and high output state leading to CHF.
• Thickened but weak bone without the normal pattern of cortical or trabecular bone. Mosaic pattern: This results in a disorganized mosaic of woven and lamellar bone. The distorted architecture weak bone which is more subject to fracture.
  • Platybasia: Flattening of base of skull
  • Bowing of femur and tibia
• Repair matches destruction hence serum calcium and phosphorus are normal
• Alkaline phosphatase elevated reflecting osteoblastic activity
• Urinary hydroxyproline is elevated reflecting increased osteoclastic activity

Stages

• an initial osteolytic stage
• a mixed osteoclastic-osteoblastic stage, which ends with a predominance of osteoblastic activity and evolves ultimately into
• a burnt-out quiescent osteosclerotic stage

Clinical picture

• Asymptomatic
  • Routine radiographs
  • Follow up for elevated alkaline phosphatase
• Pain 
• Fractures of long bone
• Headache, deafness, vertigo
• Compression of spinal cord and brain stem from invagination of base of skull
• Osteogenic sarcoma

Physical exam

As the bone expands it may cause deformities or it may cause pressure on vital structures such as nerve deafness.

• Enlarged skull: Hat size increase
• Frontal bossing
• Bowing of long bones
• Increased warmth over affected bones
• High out put CHF
• Angioid streaks in fundus

Diagnosis

• Clinical picture
• Radiographs:
  • Lytic, Sclerotic or both
  • Enlargement of Skull
  • Bowing of long bones
  • Fractures
• Elevated alkaline phosphatase with normal calcium and phosphorus
• Increased hydroxyproline

Treatment

• Salicilates or indomethacin for relief of pain
• Decrease osteoclastic activity
  • Calcitonin: GI and nasal side effects.
  • Diphosphonates: 
    • Etidronate:  Inhibits bone resorption
    • Aldronate: More potent than calcitonin and etindronate and will cause normalization of alkaline phosphotase, Side effect esophageal ulcer. Tablet is low pH reason for ulceration. To take medication in upright position with water and instructed not to lie down for thirty minutes. Food is deferred for thirty minutes to increase absorption. Calcium supplements to avoid hypocalcemia 
  • Mithramycin: activity against osteoclasts. Can cause remission.
• Orthopedic surgery