BONE DISORDERS Flashcards
Which condition would ensue in defective osteoclast activity? What would you expect to see you on an x-ray image?
Osteopetrosis
Bright white, thick bone
- Why are bones in osteopetrosis prone to fracture?
- Why might these patients develop enlarged liver and spleen?
- Why might these patients develop visual loss, deafness and facial paralysis?
- Lose balance between flexibility and strength: lose flexibility → prone to fracture
- Excess bone laid down in medullary cavity of long bones → loss of bone marrow → pancytopenia → extramedullary haematopoiesis → enlarged liver and spleen
- Excess bone in skull → cranial nerve compression
Why is bone marrow transplant potentially curable for the infantile form of osteopetrosis?
Osteoclasts are derived from monocytes and macrophages
In which two conditions is there poor mineralisation of osteoid? Explain what osteoid is and why this occurs
Ricketts and osteomalacia
► osteoid is non-mineralised bone matrix laid down by osteoblasts. It is normally later mineralised with calcium and phosphate. Seen at growth plates in children and sites of bone turnover in adults
Where are chondrocytes found?
Chondrocytes are the only cells found in healthy cartilage. Produce and maintain cartilaginous matrix, which consists mainly of collagen and proteoglycans.
What happens to the growth plates in Ricketts?
- Growth plate thickens
- Chondrocytes expand (this organised gross)
- Osteoblasts lay down osteoid only
Osteomalacia occurs at areas of high bone turnover in adults and children. They often present with bone pain and tenderness, where is this most likely to be?
Spine, pelvis, legs
A pseudofracture is an x-ray finding pathogneumonic of which condition?
Osteomalacia
What is the treatment of Ricketts disease and osteomalacia?
Calcium and vitamin D supplementation
What is the best test for vitamin D? Explain why
25-OH vitamin D (calcidiol)
→ storage version of vitamin D produced constantly by liver and available for activation (to calcitriol) by kidney as needed. Best indicator of vitamin D status as it has a long half-life and is not regulated by PTH
► if low it means person is not getting enough vitamin D through skin or diet
What would you expect ALP level to be in osteomalacia, explain why
Raised: reflects increased osteoblast activity
Which bone condition can cause enlarged head size? Explain why this happens and the stages of the condition
Paget’s disease: disorder of excessive bone remodelling causing overgrowth of bone at focal sites
caused by abnormal osteoclastic activity
- phase 1: osteolytic bone breakdown
- phase 2: mixed phase, osteolytic/osteoblastic activity
- phase 3: osteosclerotic phase, bone formation dominates. Hypervascularity of bone occurs
How does Paget’s disease lead to high output heart failure?
Increased vascularity in bones can lead to AV fistula formation → blood bypasses resistance vessels like arterioles → HF
What type of tumour at are people with Paget’s disease at increased risk of?
Osteosarcoma
What is a classic blood finding of Paget’s disease? How is the condition treated?
Raised ALP
Bisphosphonates and calcitonin
Review the approach to bone pain/fractures with regards to calcium and PTH levels
What is the classic bony manifestation of untreated primary hyperparathyroidism?
Osteitis fibrosa cystica
