Makindo Medical Notes

Related Subjects: | Bisphosphonates | Osteoporosis

About Paget's Disease of Bone

• Overactive bone metabolic turnover leads to the formation of poor-quality bone, deformity, and fractures.
• Note: There is also a distinct condition known as Paget's disease of the breast.

Aetiology

• Characterized by increased turnover of bone, osteoclastic bone resorption, and fibrosis.
• Commonly affects the pelvis, femur, lumbar spine, skull, and tibia.
• Occurs in approximately 5% of the older population in the UK.
• The cause is unknown but may be linked to a viral origin, specifically paramyxovirus.
• Osteoclasts often contain inclusion bodies.
• Incidence is decreasing over time.

Cotton Wool Skull Appearance

Clinical Features

• Involved bones are hyperaemic and warm, showing increased metabolic activity (5-10 times normal).
• Axial skeleton: Affected areas include the skull, spine, and vertebrae, leading to spinal stenosis and possible cord compression.
• Lower limbs: Deformity and fractures are common, such as bowed tibia (sabre tibia).
• Skull: Platybasia (softening of the skull base), headaches, deafness, cranial nerve palsies (VII, VIII), and hydrocephalus if the ventricular system is involved.
• Cardiac: High output cardiac failure is rare but documented.
• Deafness: Both conductive (involvement of middle ear ossicles) and sensorineural (compression of the VIII nerve).
• Cancer: Increased risk of developing osteosarcoma.
• Monostotic (one bone involved): 15% of cases.
• Polyostotic (many bones involved).

Investigations

• Blood tests typically show normal FBC, U&E, Ca, ESR, but highly elevated alkaline phosphatase (ALP).
• Vitamin D levels are generally normal.
• Skull X-Ray may show "Cotton Wool" appearance, diploic widening, osteoporosis circumscripta.
• Raised urinary hydroxyproline and pyridinoline cross-links are more specific and sensitive markers.
• Tc-99m-MDP scans are highly sensitive but not specific, useful for defining the extent of metabolically active areas.

Complications

• Rare high output cardiac failure.
• Osteosarcoma.
• Pathological fractures.
• Nerve compression symptoms.

Management

References

• Clinical Guideline for the Diagnosis and Management of Paget's Disease of Bone in Adults