Bones And Joints Flashcards
Calcium, phosphate and alkaline phosphatase alp levels in osteomalacia and rickets?
• Calcium decreased (if calciopenic cause) or normal
• phosphate decreased
. Alp increased
Name 9 causes of osteomalacia and rickets
Calciopenic
• nutritional calcium and or vitamin D deficiency, lack sunlight = most common
• anticonvulsants (accelerated 25 hydroxycholecalciferol clearance)
• CkD (impair production calcitriol - CKD-MBD)
• vitamin D dependant rickets type 1 and 2
Phosphopenic
• isolated phosphate loss, genetic
• tumour associated oncogenic osteomalacia (tumours producing fgf23)
• renal tubular phosphate leak: (most have raised FGF23, which stim renal P loss and calcitriol inhibition)
-Fanconi syndrome
-Renal tubular acidosis type 1
- hypophosphataemic “vitamin D resistant” rickets
What can be tested for to diagnose phosphopenic osteomalacia and rickets
• Plasma fgf 23 (stimulate renal phosphate loss; inhibit calcitriol)
• tubular reabsorption of phosphate
What is hypophosphatasia and how can it be differentiated from other causes of rickets
Rare inherited disorder
Also very high alp deficiency
What is hypophosphatasia and how can it be differentiated from other causes of rickets
Rare inherited disorder
Also very high alp deficiency
Name 3 clinical features of rickets and osteomalacia
•Bone pain and tenderness
• skeletal deformities, especially rickets
• proximal muscle weakness
• 50% have hypocalcaemia, others have normal due to secondary hyperparathyroidism
How is osteomalacia and rickets managed and monitored (6)
• Treat with vitamin D or one of its hydroxylated derivatives
• calcium or phosphate supplements as appropriate
• monitor: plasma calcium, phosphate, alp (will flare in first few weeks of treatments) , PTH-all should normalise
Calcium, phosphate and alkaline phosphatase alp levels in osteoporosis?
All normal! If uncomplicated
Alp only high if fracture or if comorbid osteomalacia
Define Osteoporosis
Bone mineral density > 2,5 standard deviations below the mean for young people with dexa scan
Or
Atypical fracture eg vertebral or neck of femur
Name 2 markers of bone turnover /resorption
• Pyridinium cross-links of collagen: deoxypyridinoline and pyridinoline (urine)
• cross-linking telopeptides of type 1 collagen: c-telopeptide of collagen cross-links ctx (serum)
Name 3 markers of bone formation
•Plasma osteocalcin
• bone specific or total alp = .most accessible
• procollagen type 1 terminal peptides: n-terminal P1NP and c-terminal
How can bone markers be used in osteoporosis (3)
• Monitor treatment: markers of resorption are maximally suppressed after 3 months with bisphosphOnates, while changes of bone density only detected after 2 years
• compliance
• changes in these markers correlate more closely with fracture risk reduction than changes in bone mineral density
Calcium, phosphate and alkaline phosphatase alp levels in paget disease?
• Calcium normal or increased (thick,deformed bones)
• phosphate normal
• alp very high! X 10
Calcium, phosphate and alkaline phosphatase alp, creatinine levels in ckd-mbd?
• Calcium decreased (most) (due to secondary hypoparthyroidism or osteomalacia or both ) or normal
• phosphate increased
. Alp increased
• creatinine increased
Describe the pathogenesis of ckd-mbd (7)
Nephron loss → phosphate retention
→ hyperphosphataemia → metastatic calcification and osteosclerosis!
→ hyperphosphataemia → hypocalcaemia → increased PTH secretion (secondary hyperparathyroidism) →increased bone resorption!
→ increased fgf23 synthesis → decreased calcitriol synthesis …
Nephron loss → decreased calcitriol synthesis
→ hypocalcaemia…
→ secondary hyperparathyroidism …
→ osteomalacia!
Nephron loss → acidosis → bone demineralisation!
Ie 4 bone end results
- demineralisation of bone (due to acidosis)
- osteomalacia (due to decreased calcitriol)
- incr bone resorption (due to increased PTH)
- Metastatic calcification and osteosclerosis (due to hyperP)
