Lecture 3 - finished Flashcards
Pagets Disease definition
A common, benign metabolic bone disease characterised by the thickening and disturbance of architecture of the affected bone
What is Pagets disease characterised by?
High rates of bone resorption
The formation of disorganised, immature bone
What is the pagets disease process due to?
Abnormal remodelling of bone
Pagets epidemiology
Males more than females (7:6)
Usually begins 40+ (2% of 40+ year olds)
Rare before 50yoa (1% of population over 50 have it)
By 9th decade, males = 10%, females = 15%
Prevalence of pagets in australia?
4% of the population over 55 have it. Therefore it is common.
Pagets aetiology:
Idiopathic
The theory is that genetically predisposed people will develop Pagets if they encounter certain viruses.
Slow viral infection of osteoclasts
The paramyxovirus group is thought to be involved
- measles virus
- respiratory syncytial virus
- canine distemper virus
Classifications of Pagets
Monostotic = 15%
Polystotic = 85%
Bone affected in Monostotic Pagets Disease:
Monostotic Pagets: Tibia Femur Skull Vertebrae Humerus
Bone affected in Polystotic Pagets Disease:
Polystotic Pagets: Spine Pelvis Femur Skull Sacrum Tibia Humerus
Pathology of Pagets:
Abnormal remodelling of bone
High rates of bone resorption
Disorganised immature bone formation
Increased vascularity of affected bones
Stages of Pagets Disease
1 - Osteolytic
2 - Mixed Osteolytic/osteoblastic
3 - Osteosclerotic
Describe the osteolytic phase of Pagets Disease
Normal bone is resorbed by abnormal osteoclasts.
These osteoclasts are bigger, more numerous, have more nuclei than normal, and contain micro cylindrical inclusions.
Bone turn over rate can be up to 20 times normal.
Describe the mixed osteolytic/osteoblastic phase of pagets
Resorption is closely followed by new bone formation but they are uncoupled/ don’t occur in a balanced fashion.
New matrix is haphazardly laid down as woven bone.
Bone volume remains mostly normal.
As a result:
- mineralisation of matrix lags
- osteoid seams persist, demarcating the margins of newly laid bone
- tile like/mosaic pattern of bone formation is pathognomonic
- new bone is highly vascularised
- adjacent bone marrow spaces fill with loose, highly vascularised connective tissue
UNCOUPLED IS THE KEY WORD IN THIS STAGE
Describe the osteosclerotic phase of pagets
After many years in stage 2, the condition burns out/becomes quiescent.
Key features of this stage:
- formation of new bone is
= disordered
= poorly mineralised
= of poor structural stability
= vulnerable to fracture and deformation
- osteosclerosisWhat are the macroscopic features seen in the osteosclerotic phase of Pagets disease?
Anterior bowing of long bones Sagging of femoral neck Enlarged, deformed skull Coarsened facial bones (leontiasis ossea) Vertebral: - cortical thickening - trabeculae coarsening - poorly formed bone - tendency to collapse leading to kyphosis
What are the structural properties of pagets affected bones?
Bone is:
- soft
- porous
- eventually enlarges
The bone has:
- poor structural stability
- an increased risk of deformity
- an increased risk of fracture
What are the clinical manifestation of Pagets disease
Asymptomatic (usually monostotic form)
Pain (most common ssx, mostly occurs in the polystotic form, due to #, nerve compression and secondary OA)
Bone deformity
- skull enlargment
- femur and tibial bowing
- facial bones (leontiasis ossea)
- vertebral # and collapse
Bone enlargement
Warmth over affected bones (increased vascularity)
Sponginess of bones on palpation
Neurological manifestations
What are some neurological ssx that may occur with pagets and why?
Expanding bone may put pressure on nerves, the brain or spinal cord resulting in:
- headache
- hearing loss/tinnitus
- visual disturbances
- various neuropathies
What are the radiological findings of pagets?
Osteolytic phase = flame lesions (patchy radiolucent lesions)
Sclerotic stage = irregular sclerosis
Later stages = bone enlargement
What are the complications of Pagets disease:
Musculoskeletal:
- pain
- bone deformity
- pathological #
- secondary OA
Neurological:
- nerve compression (ie carpal tunnel, sensorineural deficits)
- radiculopathy
- spinal stenosis and myelopathy
Cardiovascular:
- increased CO because of the increased vascularisation of the lesions puts more strain on the heart. Can lead to altherosclerosis, CHF, aortic valve calcification etc.
Neoplastic:
- Osteosarcoma
Fibrous dysplasia definition
A benign focal slowly expanding lesion in which bone in slowly replaced by a mass of fibroblasts, collagen and irregular bone trabeculae of woven bone.
Fibrous dysplasia is a focus of disordered maturation of bone with arrest at the immature stage of woven bone
What are the 3 types of fibrous dysplasia?
Monostotic
Polystotic
Albrights Disease
Describe monostotic fibrous dysplasia
Epidemiology Sites of involvement Aetiology Pathology Clinical manifestations
Epidemiology:
- 70% of cases
- Both sexes equally
- Usually begins at childhood with progression often stopping its progress at puberty.
Sites of involvement:
- ribs (most common)
- femur
- tibia
- mandible
- maxilla
Aetiology:
increased osteoclast numbers
increased fibroblast numbers
Pathology:
- Affected bone is replaced by:
= proliferating fibroblasts
= scattered trabeculae of irregular woven bone
- the usual rim of osteoblasts around the bone trabeculae is absent
Clinical manifestations: - usually asymptomatic - the lesion may cause = tumourous distortion of the bone = disfigurement of face/skull = pain
Describe polystotic fibrous dysplasia
Epidemiology
Sites of involvement
Clinical manifestations
Epidemiology:
- 25% of cases
- both sexes equally
- appears at an earlier age than monostotic
Sites of involvement:
- uni or bilateral
- femur (most common)
- skull
- tibia
- humerus
- ribs
Clinical manifestations:
- craniofacial bones affected in 50% with moderate disease and 100% in patients with extensive disease
- shoulder and pelvic girdles severely affected
- multiple skeletal deformities seen
- pain due to fractures (characteristic)
What is Albrights disease:
• A form of polystotic fibrous dysplasia with
○ Multiple unilateral bone lesions
○ Unilateral pigmented skin lesions
○ Autonomous endocrine hyperfunction
• Some endocrinopathies seen are:
○ Acromegaly
○ Hyperthyroidism
○ Cushings syndrome
Skin lesions usually on same side of the body as the bone lesions and are large pigmented areas of dark coloured “café-au-lait”, irregular serpiginous borders
Describe the typical bone lesion in fibrous dysplasia
Affected bone is replaced by proliferating fibroblasts, amongst which are scattered trabeculae of irregular woven bone. The usual rim of osteoblasts around the bone trabeculae is absent.
Describe a lytic lesion:
A well circumscribed lesion of reduced bone density positioned in the medullary regions of the bone. Might see slight expansion of the bone and cortex but wont see any erosion of the cortex by the lesion.
There will be no evidence of trabecular bone but will have speckled ‘ground glass’ type of appearance.
What are the radiological manifestations of fibrous dysplasia?
Usually presents as a lytic bone lesion (bone cyst)
Affected bone has a ‘ground glass’ radiolucent appearance. The lesion is well demarcated from normal bone.
What are the complications of fibrous dysplasia?
Pathological #
Osteosarcoma (rare)
