Metabolic bone disease Flashcards
Most common metabolic bone diseases.
a) 1st
b) 2nd
c) 3rd
a) Osteoporosis
b) Paget’s disease of bone
c) Osteomalacia
Woman (71) develops acute onset back pain from a vertebral fracture. She has a bone density measurement that confirms the diagnosis. What is it?
Osteoporosis: low bone mass
Man (79) presents with groin pain. X-ray shows a deformed, dense femur. Isotope bone scan shows increased isotope uptake in femur.
Most likely diagnosis?
Paget’s disease
Note: Pagets and prostate cancer both cause in increase in bone density on xrays, but only Paget’s causes an increase in bone size (bigger vertebrae, wider femoral shafts etc)
Bone metastases.
a) Osteolytic
b) Osteoblastic/sclerotic
c) Mixed
a) SCLC, renal cancer, myeloma, melanoma, NHL, thyroid ca
b) Prostate, HL, NSCLC
c) Breast (mainly lytic), GI cancers
Woman presented to ED with overdose of anti-convulsant therapy. Pain in hands and feet too severe to tolerate. Unable to stand without help
X-rays of hands (and feet) showed pseudo-fractures.
Diagnosis?
Osteomalacia: low bone mineralisation leading to softening of bones and may result in painful deformation and pseudofractures
Osteomalacia.
a) Diagnosis
b) Management
a) ???
b) The underlying cause needs to be treated, encourage housebound people to go outside in the summer,
give calcium along with vitamin D supplements, monitor the biochemical response to make sure treatment effective (Serum calcium, alkaline phosphatase, etc)
Osteomalacia: causes
- Housebound (lack of sunshine on skin)
- Asian immigrants (lack of sunshine on skin)
- Epileptics on anticonvulsants (increased rate of catabolism of vitamin D by liver)
- Malabsorption syndrome (poor absorption, and loss of vitamin D in faeces)
- Chronic renal failure (failure to activate vitamin D)
Osteomalacia: consequences
a) Signs and symptoms
b) Biochemical
a) - Hypocalcaemia: Tetany, Chvostek’s and Trousseau’s signs
- Osteomalacia: Bone deformity and pain,
- Rickets: Short stature, bone deformity and pain
- Muscle weakness
- Proximal myopathy
b) Low serum Ca2+, low vit D, high PTH, low phosphate (due to raised PTH and increased renal excretion), raised Alk Phos.
Vit D biosynthesis.
a) In UVB - the skin synthesises…?
b) Converted to _____ in the liver by the enzyme ____.
c) The kidneys convert this to the active form of vitamin D (______) with the enzyme ______.
a) 7-dehydrocholesterol
b) 25-hydroxyvitamin D; 25-hydroxylase
c) 1, 25-hydroxyvitamin D (calcitriol); 1-alpha-hydroxylase
Dose/administration of Vitamin D according to condition.
a) Housebound/Asian
b) Epileptics on anticonvulsants
c) Malabsorption
d) Renal failure
a) Physiological dose, oral
b) High dose, oral
c) High dose, IM injections
d) Calcitriol (active vitamin D, as they cannot produce it)
Paget’s disease: presentation
Asymptomatic
Symptomatic:
- Bone pain
- Complications: Skull (deafness), Surgery planned (reduce the risk of excessive blood loss), Spinal cord compression
- Isolated raised ALP (calcium and phosphate usually normal)
- XR findings: Bigger bones - thickened vault, wider femoral shafts, larger vertebrae
Paget’s: management
a) diagnosis
b) follow-up
c) treatment
a) Isotope bone scan allows identification of the bones that are affected (the bones affected at diagnosis are those affected for life; do not change)
b) Serum Alk Phos allows the disease activity to be monitored
c) - Bisphosphonates: zoledronate (IV)/risedronate (PO)
Manage complications in their own right.
Analgesics for pain, joint replacement for severe joint degeneration, etc.
Osteoporosis:
a) Diagnosis
b) 4 typical fractures
c)
a) T-score 2.5 SDs below mean on hip BMD scan
b) NOF, vertebral, distal radial (Colles’/ Smith’s)
FRAX score
???
Bisphosphonates.
a) MoA
b) Administration - oral versions
c) IV version
a) Anti-resorptive (turn off osteoclastic activity); reduce fracture risk by 50%
b) Morning, with water, upright for 30 mins (prevent oesophagitis)
c) Zoledronic acid (may cause flu-like illness)
