Usually identified as an incidental finding on an x-ray or other imaging study, it is a disease of overgrowth of bone. Bone is seen as woven and expansile. It can cause pain. It can elevate bone enzymes, alkaline phosphatase and bone-specific alkaline phosphatase. It usually is seen in older, white men. It can be treated but doesn't always (usually?) require intervention. It can cause bone cancer (osteosarcoma).
Pathology/Science
Paget disease of bone (PDB), is characterized by an accelerated rate of bone remodeling resulting in overgrowth of bone at selected sites and impaired integrity of affected bone.
It is believed to be a disease of the osteoclast.
Osteoclasts resorb bone.
Receptor activator for nuclear factor kappa-B ligand (RANKL) and macrophage colony-stimulating factor (MCSF) cause osteoclast differentiation.
RANKL binds to its receptor, RANK, on osteoclast precursors to promote osteoclast differentiation and activation via activation of nuclear factor kappa-B (NFkB)-dependent pathways.
Osteoprotegerin (OPG; a soluble decoy receptor for RANKL) inhibits osteoclast differentiation - modulated by cytokines and hormones. [1]
Imaging
X-ray findings
"Osteoporosis circumscripta," osteolytic lesions that may be seen in the skull in early disease
Mixed lytic/sclerotic lesions, which gradually progress over time, resulting in thickening of cortical bone, heightened trabecular markings, and distortion and overgrowth of involved bone
Progression of lesions originating in the subchondral bone and moving in one direction through the bone in a pattern sometimes described as "flame shaped," with cortical tunneling and trabecular thickening sometimes present
Pseudofractures, small fissures on the convex surface of long bones affected by bowing.
Very infrequent identification of new bone lesions over time, although individual lesions evolve as noted above
Pelvic involvement results in protrusio acetabuli, which can give the pelvis a triangular appearance.
Iliopectineal line involvement, which is sometimes described as appearing in the shape of the number "3."
Ivory appearance of the affected spine in some patients. An affected vertebra is often enlarged in all three planes or may have the appearance of a picture frame. Additionally, vertebral enlargement may cause a loss of the normal lumbar lordosis and may accentuate the dorsal kyphosis.[1]
How to monitor
Patients not treated with antipagetic agents
In patients with a normal serum alkaline phosphatase in whom a pagetic lesion has been detected incidentally, but in whom treatment is not determined to be appropriate, monitor the patient yearly for bone pain, functional impairment, and elevation of serum alkaline phosphatase. [2]
Treatment
References
[1] J Charles. Clinical manifestations and diagnosis of Paget disease of bone. Uptodate [2] J Charles. Treatment of Paget disease of bone. Uptodate
