Flashcards in Acquired Bone Disorders Deck (47)
What is osteoporosis?
a reduction in trabecular bone mass resulting in porous bone with an increased risk of fracture and increased marrow space (that fills with fat mostly)
What are the most common forms of osteoporosis?
senile and postmenopausal
How does menopause decrease bone mass?
-decreased serum estrogen
-increased IL-1, IL-6, and TNF levels
-increased expression of RANK, RANKL and increased osteoclast activity
How does aging decrease bone mass?
there is decreased replicative activity of osteoprogenitor cells, osteoblast activity, activity of matrix-bound growth factors, as well as reduced physical activity
What causes type 1 (postmenopausal) osteoporosis?
decreased osteoblastic activity
What causes type 2 (senile) osteoporosis?
increased osteoclastic activity
What is a very common fracture with osteoporosis?
proximal femoral fractures (high mortality in older adults). Note, a fall to the side increases the risk of hip fracture by about 6 times compared to falls in other directions
What is a common treatment for osteoporosis?
Bisphosphates (also good for Paget's disease)
How do bisphosphates work?
they bind to hydroxyoptite and inhibits osteoclast activity
AEs of bisphosphates?
1) corrosive esophagitis- take with water and remain upright for at least 30 minutes
2) osteonecrosis of the jaw
What is osteomyelitis?
infection (most often bacterial) of the bone, typically in children caused from direct inoculation (trauma), contiguous spread (cellulitis), or blood spread
How does osteomyelitis present?
bone pain with systemic signs of infection
How does chronic osteomyelitis appear on x-ray (this is the best imaging for chronic)?
lytic abscess (aka sequestrum) surrounded by sclerosis of bone (aka involurum)
How does acute osteomyelitis appear on MRI (this is the best imaging for acute)?
T or F. Get blood cultures before treating osteomyelitis
will commonly see elevated CRP and ESR (but not specific)
What is the most common cause of osteomyelitis?
Staph aureus (90%)
What is the most common cause of osteomyelitis in sexually active young adults?
What is the most common cause of osteomyelitis in sickle cell patients?
What is the most common cause of osteomyelitis in diabetics or IVDUs?
Pseudomonas (or candida or staph aureus)
What is the most common cause of osteomyelitis of the spine (Pott's Disease)?
Mycobacterium TB (giant cells without necrosis)
What is the most common cause of osteomyelitis with prosthetic limbs/joints?
What is the most common cause of osteomyelitis from dog and cat bites?
What are a few common pathologies that raise ESR over 100mm/hr?
-Osteomyelitis (staph aureus mostly)
What is the common end pathway for any pathology that disrupts vascular supply to the femoral head?
What are some common causes of avascular necrosis/osteonecrosis?
-decompression sickness (the bends)
What are some common causes of avascular necrosis/osteonecrosis in 4-10 yo boys?
legg calve-perthes disease (idiopathic)
What is Paget's disease? Presentation
typically localized imbalance (increased) of osteoclast and osteoblast function-thick bone (idiopathic, possibly viral). Can be widespread
Patients might present with hearing loss (due to narrowing of the auditory foramen), bow legs, kyphosis or increased hat size
What is a suspected genetic cause of Paget's disease?
chromosome 18 mutations
Paget's disease is the most common cause of what?
isolated elevated alkaline phosphatase in patients over 40 yo
Paget's disease carries an increased risk of what?
osteosarcoma, increased AV shunts (heart failure), long bone fracture
T or F. Serum Ca2+ and PTH are normal in Paget's disease
What are the phases of Paget Disease?
1) lytic- osteoclasts predominate
2) mixed- neither predominate
3) sclerotic- osteoblasts predominate
leads to thick bones that fracture easily
Skulls can take on a ____ appearance in Paget's disease
What is Osteomalacia (adults)/rickets (kids)?
inadequate mineralization of osteoid leads to weak bones and fractures due to vitamin D deficiency leading to soft, bowing bones
How do osteomalacia/rickets present in labs?
-decreased vitD, serum Ca2+ and phosphate (PO4)
-increased PTH and alkaline phosphate (due to increased osteoblast activity which need an alkaline environment)
What stain can be sued to ID osteomalacia/rickets?
von Kossa stain: calcified tissue is black and they are covered by a layer of unmineralized osteoid (dark pink)
T or F. There is abundant osteoid in Osteomalacia/rickets but it is not mineralized
T. Causing the bone to be weak and increase risk of fracture
What causes primary hyperparathyroidism?
hyperplasia or tumor (adenoma) of the parathyroid gland
What causes secondary hyperparathyroidism?
prolonged states of hypocalcemia due to chronic renal failure with resulting hyper secretion of PTH
What does increased PTH cause?
it is detected by osteoBLasts which stimulate osteoclasts leading to unabated bone resorption causing cyst-like brown tumors within the bone
What do the cyst-like brown tumors consist of?
fibrous tissue and woven bone without matrix
Why do the tumors of hyperparathyroidism take on a brown appearance?
there is cyst formation within the bone making it prone to hemorrhage which then turns brown from residual hemosiderin
Labs with hyperparathryoidism?
increased PTH and
x-ray changed consistent with osteopenia
secondayr will show decreased GFR
What is osteitis fibrosa cystica (von Recklinghausen disease of bone)?
rare progressive disease of hyperparathyroidism with triad of:
-increase bone cell activity
-cystic brown tumors
not seen often
What is renal osteodystrophy?
collectively describes skeletal changes associated with chronic renal disease when the kidney cannot convert vitamin D to active form
What does renal osteodystrophy encompass?
-increased osteoclastic bone respiration mimicking osteitis fibrosis cystica
-delayed matrix mineralization (osteomalacia)