Chronic condition involving cellular remodeling and deformity of one or more bones
Aetiology
Cause uncertain
Genetic elements that increase activity of Nf ⲕβ
Viral infection may play a role
Rare in people < 50 years
Predominantly affects long bones, pelvis, lumbar spine and skull
Pathophysiology
Abnormal osteoclastic activity followed by increased osteoblastic activity results in abnormal bone structure with reduced strength and increased fracture risk
May be single site (monostotic) or multiple sites (polyostotic)
Three stages:
Osteolytic - restoration pits with large osteoclasts
Mixed - osteoclasis and osteoblastic activity
Osteosclerotic
Effect on bone
Net result is thick excess bone with abnormal reversal lines - mosaic pattern
Bone matures but is soft and porous
Can affect all bones - usually axial, small bones less commonly affected
Clinical presentation
Often asymptomatic
Pain - micro-fracture or nerve compression
Enlargement and abnormal shape of bone → leontiasis ossea, platybasia, sabre tibia
Increased metabolism → heat (warm skin), AV shunt, effectively high output heart failure
Investigations
X-ray
Initial lytic phase results in well defined lucency
Later sclerotic phase with enlarged bone, increased density and coarse trabecular pattern
Isotope bone scan - shows distribution of disease
Biochemistry - ↑ alkaline phosphatase with otherwise normal LFTs
Management
Treat with bisphosphonates if pain not responding to analgesia
Complications
Risk of secondary malignancy within the affected bone - osteosarcoma, fibrosarcoma
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