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pathoma
MSK- skeletal system
| Question | Answer |
|---|---|
| impaired cartilage proliferation at the growth plates is called what? | achondroplasia |
| what characteristic genetic problem causes achondroplasia? | ***an activating mutation in the fibroblast growth factor receptor (FGFR3) AD. the overexpression of FGFR3 will inhibit growth |
| whats a risk factor for getting this mutation in FGFR3? | increased paternal age |
| what are the clinical features of achondroplasia? | short extremities with normal sized head and chest (d/t poor endochondral bone formation; IM bone formation is NOT affected) |
| what is endochondral bone formation? | formation of cartilage matrix which is replaced by bone; its the mechanism by which long bones grow. |
| what is intramembranous bone formation? | characterized by formation of bone without a pre-existing cartilage matrix; itsthe mechanism by which flat bones (skull, and rib cage-chest) develop |
| are mental function, life span or fertility affected in achondroplasia? | NOPE |
| congenital defect in bone resorption causing structurally weak bones is called what? | osteogenesis imperfecta |
| where is the defect causing osteogenesis imperfecta? | AD type 1 collagen defect |
| clinical features of osteogenesis imperfecta? | multiple fractures of the bone (can mimic child abuse- but no bruising present), blue sclera- thinning of scleral collagen exposing choroidal veins, hearing loss- when bones of the middle ear fracture |
| what is osteopetrosis? | inherited defect of bone RESORPTION = abnormally thick, heavy bone that fractures easily. d/t poor osteoCLAST function |
| explain how carbonic anhydrase 2 mutation causes osteopetrosis | carbonic anhydrase 2 mutation leads to loss of acidic environment that's required for bone resorption (CA catalyzes the reaction of H20 and CO2 to H2CO3 to get to H and HCO3 to make acid) |
| clinical features of osteopetrosis | bone fractures, anemia, thrombocytopenia, leukopenia (w extramedullar hematopoiesis d/t bone replacement of marrow) vision and hearing impairment (d/t impinging CN) hydrocephalus (narrowing foramen magnum) and RTA |
| how does osteopetrosis cause RTA? | the carbonic anhydrase 2 mutation,the lack of carbonic anhydrase results in decreased tubular reabsorption of HCO3 = metabolic acidosis. |
| what is the treatment for osteopetrosis? | bone marrow replacement- bc we need new osteoclasts which are made from monocytes which are made from hematopoietic cells |
| defective mineralization of osteoid is called what? | rickets/osteomalacia |
| what normally produces osteoid? | osteoblasts. they prod the osteoid which is then mineralized w Ca and Phosphate to form bone |
| how does low vit D cause rickets? | bc this decreases your ca and phosphate |
| how do we get vit D (2 sources) | 1. sunlight (85%) 2. diet (15%) |
| what 2 things are required by liver and kidney to activate vit d? | 25-hydroxylation by the liver followed by 1ahydroxylation by the PT of kidney |
| where does vitD act to increase body ca and phosphate? | intestine, kidney,and bone. |
| what things cause vit d deficiency? | lack of sunlight exposure, diet deficiency, malabsorption, liver or renal failure |
| rickets is d/t low vit D is who? | children <1YO |
| what are clinical findings of rickets? | pigeon breast deformity- inward bending of ribs with anterior protrusion of the sterum. frontal bossing- (enlarged forehead) d/tosteiod deposition on the skull. rachitic rosary- osteiod deposition at costochondral junction,bowing of legs |
| low vit D is in adults is called what | osteomalacia |
| lab findings of osteomalacia? | decreased serum ca, phosphate, INC PTH and alkaline phosphatase (is increased whenever theres a lot of osteoblast activity- alkaline environ is necessary to lay down ca) |
| osteoporosis is a reduction in what type of bone/ | trabecular bone (left with porous bone with increased risk for fx) |
| what is the risk of osteoporosis based off of? | peak bone mass- and the rate of bone loss that follows |
| what age do you have peak bone mass, what is it based on? | 30YO. genetics (ie-vitD rec variants) diet and exercise |
| after your PBM how much bone are you losing? | less than 1% of bone mass lost each year after. its lost quicker when you are not doing weight bearing exercise, poor diet and decreased estrogen-menopause |
| what are the most common forms of osteoporosis? | senile and postmenopausal |
| clincal features of osteoporosis? | bone pain/fx in weight bearing exercises- pain in vertebra, hip and distal radius, bone density measured by DEXA scan, serum ca, p, PTH and alkaline phosphatase are NORMAL. ** |
| treatment for osteoporosis? | exercise, vitD and ca, bisphosphonates, estrogen replacement tx, (debated), glucocorticoids are CONTRAINDICATED- induce osteoporosis |
| why do bisphosphonates help in osteoporosis/ | they induce apoptosis of osteoclasts |
| imbalance between bone loss and gain is what disease? | pagets |
| what age is pagets normally found? | >60YO, late adulthood |
| does pagets involve the whole skeleton? | NO. only involves 1 or more bones. |
| 3 stages of pagets disease? | osteoclasts, mixed osteoblast/clast, and then osteoblasts... resulting in thick,sclerotic bone that fx easily |
| what does biopsy show in pagets bone disease? | mosaic pattern of lamellar bone |
| clinical features of pagets disease? | bone pain (d/t microfx), increasing hat size, hearing loss (impinge on CN), lion like facies (thickened facial bones), isolated elevated alk phosphatase- MC cause of isolated elevated alk phos in pt >40YO. |
| treatment of paget disease? | calcitonin will inhibit osteoclast function and bisphosphonates induce apoptosis of osteoclasts |
| complications of pagets disease/ | high output cardiac failure (d/t AV shunt formation) and osteosarcoma |
| osteomyelitis is ..>? | an infection of marrow and bone that normally occurs in children |
| what are the causative agents of osteomyelitis? | bacteria mostly. s. aureus is MC. N.gonorrhea (in young sexually active), salmonella (sickle cell disease), pseudomonas (DM or IV drug abusers), pasteurella (assoc with cat/dog bites), mycobacterium tuberculosis (involves vertebrae-pott disease) |
| what is the difference of osteomyelitis in children as compared to adults? | in children transient bacteremia is in the metaphysis and in adults open would bacteremia is in epiphysis |
| clinical features of osteomyelitis? | bone pain with systemic signs of infeciton- fever and leukocytosis. lytic focus (abscess) surrounded by sclerosis of bone on xray, lytic focus is called- sequestrum and sclerosis is called involucrum |
| diagnosis of osteomyeltis is done by what? | blood culture |
| avascular (aseptic) necrosis of the bone is caused by what | trauma/fx, steroids, sickle cell anemia, and caisson disease (gas emboli into the bone) |
| what are major complications of avascular septic necrosis? | osteoarthritis and fracture |
| 3 major things we should know about an OSTEOMA | its benign tumor of the bone, MC arises on surface of FACIAL BONES, and its associated with Gardners syndrome |
| whats an osteoid osteoma characterized by? | benign tumor of osteoblasts (prod the osteoid) thats surrounded by a rim of reactive bone |
| what age does osteiod osteoma occur? | <25YO, more common in males. |
| where does osteoid osteomas occur? | cortex of long bones. |
| presentation of osteoid osteoma/ | bone pain relieved with aspirin |
| what do you see on imaging of osteoid osteoma? | bony mass (<2cm) w radiolucent core (osteoid) |
| what are the differences btw osteoblastoma and osteiod osteoma? | osteoblastoma is larger (than 2cm), arises in vertebra, and presents as bone pain UNrelieved by aspirin |
| tumor of bone w overlying cartilage cap thats the most common benign tumor of bone is called what? | osteochondroma |
| where does osteochondroma arise? | from lateral projection of growth plat,bone is continuous with the marrow space |
| malignant proliferation of osteoblasts? | osteosarcoma |
| what is the peak age incidence of osteosarcoma? | teenagers- less common in the elderly. |
| risk factors for osteosarcoma? | familial retinoblastoma, pagets disease, and radiation exposure. |
| where does osteosarcoma arise? | metaphysis of long bones- distal femur or proximal tibia |
| imaging of osteosarcoma shows what? | destructive mass with 'sunburst' appearance and lifting of periosteum- codman angle** |
| what is the only tumor that we need to know that arises in the epipysis of long bones? | giant cell tumor |
| what do you see on xray of giant cell tumor? | soap bubble appearance |
| what type of cells does ewing sarcoma derive from/ | neuroectoderm |
| where does ewing sarcoma arise? | diaphysis of long bones- usually male children <15YO |
| what do you see on xray for ewing sarcoma? | onion skinning |
| biopsy of ewing sarcoma? | small, round blue cells thatresemble lymphocytes |
| whats the genetic mutation of ewing sarcoma? | T (11;22) |
| chondroma is benign tumor of cartilage arising in | medulla of SMALL BONES- hands and feet |
| chondrosarcoma is malignant cartilage forming tumor that arises in | medulla of the pelvis or central skeleton |
| metastatic tumors result in what lesions? whats the exception? | osteolytic (punched out) lesions. exception- prostate CA- has osteoblastic lesions. |
Created by:
afrank1