A. Paget’s disease – Explanation

Note that the patches of the skull are sclerotic and not lytic. Sclerotic patches represent
Paget’s disease (osteitis deformans) whereas if it was lytic lesions on the skull it would
represent multiple myeloma. Alkaline phosphatase is seen to be raised in both Paget’s
disease and multiple myeloma however it is usually seen raised in multiple myeloma
only when associated with fractures.

Note that there are two types of Paget’s disease:
1. Paget’s disease of the bone (osteitis deformans)
2. Paget’s disease of the breast

Paget’s disease (osteitis deformans)
Think of Paget’s disease as a bone-making process (bone turnover) becoming faster
and out of control. There is increased bone resorption and abnormal osteoclast activity
followed by rapid increase in bone formation by osteoblast. The new bone structure
ends up being disorganised and mechanically weaker, more bulky, less compact, more
vascular, and liable to pathological fracture and deformity.

Paget’s disease can affect any bone but is most common in the axial skeleton, long
bones, and the skull. The usual sites are the pelvis, lumbar spine, femur, skull and tibia.

Presentation

• It is commonly asymptomatic and is discovered by the incidental finding of an
  elevated serum alkaline phosphatase or characteristic abnormality on X-ray
• When symptoms occur, the most common complaints are bone pain and/or
  deformity
• Bone pain may be present at rest and on movement
• Bone deformity includes sabre tibia (bowing of the tibia), kyphosis, and frontal
  bossing of the skull.
• Other presentations include pathological fractures
• Deafness and tinnitus may be due to compression of cranial nerve VIII
• High-output cardiac failure (due to increased blood flow through affected bone)

Investigations

• There are specific X-ray features of Paget’s disease that include:
• A classical V-shaped pattern between healthy and diseased long bones known
  as ‘the blade of grass’ lesion
• The ‘cotton wool’ pattern in the skull that is also characteristic (multifocal sclerotic
  patches)
• Serum calcium and parathyroid hormone levels are usually normal but
  immobilisation may lead to hypercalcaemia

• Alkaline phosphatase is markedly raised

Note: Osteosarcoma is one of the complications thus Paget’s needs to be monitored
closely.
Management
Bisphosphonates

COMPARING OSTEOPOROSIS, PAGET’S DISEASE AND OSTEOMALACIA