Congential Acquired Dz Flashcards
What is the composition of bone?
65% inorganic - Ca hydroxyapatite – strength/hardness
35% - organic - Collagen = structure
What is osteoid?
nonmineralized bone, takes 12-15 days to mineralize
What are the various bone cell types?
- osteoprogenitor cells- become osteoblasts w/ CFBA1
- osteoblast - mononuclear
- Osteoclast - multinucleated
- osteocytes - mechanical stress, regulate serum Ca and phosphorous
What do osteoblasts do?
make osteoid; they are eventually surrounded by matrix, have PTH receptors (squamous cell carcinoma), feedback mechanisms for osteoclasts
Where are osteocytes found/
encased in bone, communicate via canaliculi
What do osteoclasts do?
- remodel, require cytokines for differentiation
2. resides in resorption pits
What cytokines do osteoclasts need for differentiation?
IL 1, 3, 6, 11, GMCSF, and MCSF
Interplay btw osteoblasts and clasts?
- osteoblasts and stromal cells have RANKL which binds to clasts RANKL-receptor w/ MCSF and makes functional osteoclasts.
- stromal cells also secrete OPG
What is OPG
decoy receptor for RANKL = prevents bone resorption, inhibits clast differentation
What happens in mature bone?
- epiphyseal plate ceased to grow
- metaphyseal vessels penetrate cartilage plate
- transverse bars of bone separate plate from metaphysis
What is osteogenesis Imperfecta?
- brittle bone dz, type 1 collagen mutations, teeth deformed, mostly AD
- different types exists - know that type 2 and 3 are fatal to kids
What are the 4 major clincal criteria for OI?
- osteoporosis
- blue sclera ( due to thinning of scerla allows underlying choroid to become visible)
- dentingenesis imperfecta
- premature otosclerosis
What is achondroplasia?
impaired formation of long bone, locus = FGF3 receptor, most are due to new mutations that are AD. Features = large forehead, prominent supraoribtal ridges, deep set root of nose
What is osteopetrosis?
- marble bone dz; osteoclast dysfunction = CA II deficiency??
- long bones w/ out medullary cavity, bullous ends, irregular trabeculae, woven bond = more prone to fractures
- most severe form = ARO
- Rx w/ osteoclast precursor via BMT
- pts are neutropenic and anemia
What is the pathogensis for osteopetrosis?
osteoclasts can’t resorb bone so bone marrow is occulded by weak, woven bone. the number of osteoclasts are normal. You can have a LOF mutation of RANKL.
What is osteoporosis?
systemic dz w/ low bone mass and microarchitectural deterioration of bone tissue (tin trabuclae w/ microfractures)
How is the peak bone mass affected in osteoporosis?
- Menopause - decreases in estrogen, increases in RANKL, and increases in IL1/6/TNF
- Aging - decrease in osteoprogenitor replication, decrease in osteoblasts, decreased biologic activity of matrix bound GFs, decreased physical activity
What is Paget’s dz of bone?
- unbalance and excessive osteoclast/blast function = increased bone turnover
- northern europeans
- paramyoviruses or measles
- mosaic pattern of lamellar bone
- predisposed to sarcoma
- irregular thick coarse cortex of bone
What features are present in pagets dz?
- thick skull
- deafness
- kyphosis
- pain
- bowed legs
What is osteomalacia?
- bone doesn’t mineralize due to not enough Vit D and/or Ca
- rickets in kids
- surface of bony trabeculae covered by thicker than normal layer of osteoid
What are some causes of osteomalacia?
- Renal osteodystrophy - can’t make 1,25(OH) vit d due to tubular injury = hypocalcemia.
- HyperPTHism - increased PTH, Ca and increased Ca release fro bone, phosphate retention. Brown Tumor!!!
- decreased total bone mass
- increased bone formation in spine/long bones
What is osteitis fibrosa cystica
increased bone activity and peritrabeular fibrosis and cystic brown tumors
What are brown tumors caused by
Macs react to microfracturees and hemorrhage - hemosiderin deposits and fibrosis ensues
