12. USMLE MSK III
Terms in this set (65)
what type of crystals precipitate into joints in gout? what causes it?
monosodium urate crystals; hyperuricemia
what percentage of hyperuricemia is d/t underexcretion? overproduction?
what are some diseases that can cause hyperuricemia?
Lesch Nyhan Syndrome (decreased HGPRT); thiazide diuretics (decreased excretion of uric acids); psoriasis (increased cell turnover like leukemia); von Gierkes disease; lead poisoning (excretion competes with uric acid)
what acidotic state can precipitate gout? why?
alcoholic lactic acidosis because the lactic acid competes with the uric acid
what happens to the crystals once they have been deposited in the joints?
neutrophils phagocytose the crystals
what shapes are monosodium urate crystals? in parallel light are they negatively or postively biferingent? yellow or blue?
needle shaped; negatively; yellow
what is the presentation of gout?
usually men; asymmetric joint distribution; joint is swollen, red, and painful- usually MTP joint of big toe (podagra)
where does tophus formation usually occur in gout? where does it usually occur?
external ear, olecranon bursa, or Achilles tendon; usually seen in chronic gout- its a uric acid crystals that have not only accumulated in the joint but also in the periarticular tissue and causes multinuc giant cells
what can precipitate an acute attack of gout?
large meal or alcohol consumption
what can urate crystals do to the kidney?
urate nephropathy and renal stones
is gout progressive? when do you treat?
no; only treat if tophaceous deposits exist
what is the acute treatment of gout? mech of action?
usually just NSAIDs (indomethacin) and colchicine (M phase- microtubular polymerization inhibitor)
what is the chronic treatment of gout?
allopurinol and uricosurics (probenecid)
when should uricosurics be avoided?
in patients who excreted excrete large amounts of uric acid
what kind of crystals deposit in pseudogout?what shape are they? are they positive or negative bifirengent in parallel light?
calcium pyrophosphate crystals; rhomboid basophillic- positively biferengent; blue
what is the classic presentation of pseudogout? what is the cause? how do you treat? what do you see on radiograph?
both men and women equally affected in large joints (knee); whenever calcium or phosphate increased which causes deposition in synovial fluid; no treatment; chondrocalcinosis on radiograph- linear deposits of calcium pyrophosphate in articular cartilage
what are three main causes of septic infectious arthritis?
S. aureus, Streptococcus, Neisseria gonnorrhoeae
how does gonococcal arthritis present?
monoarticular, migratory, asymmetric often in the knee, hand (tenosynovitis) and with dermatitis (pustules on the wrists and ankles)
what are two causes of chronic infectious arthritis?
what is seen on exam and xray in a male patient with psoriases coming in with joint pain and stiffness? what type of arthritis is its/
extensive nail pittin, dactylitis "sausage" fingers and "pencil in cup" deformity on x ray; HLA 27 seronegative spondyloarthropathy
what type of disease is ankylosing spondylitis? how does it usually present?
seronegative spondyloarthropathies (HLA B27- MHC I encoder); sacroiliac joints fuse (ankylosis) causing bamboo spine on radiography, uveitis, and aortic regurg
what are the extra-MSK symptoms in ankylosing spondylitis?
uveitis, aortic regurg
what does the ankylosing in ankylosing spondylitis cause other than bamboo spine with forward curvature?
kyphosis (cause nonpulmonary restrictive lung disease)
an arthropathy with blood diarrhea is usually what?
IBD with seronegative spondyloarthropathy
what if a patient with shigellosis presents with conjunctivitis and arthritis as well what type of disease is it? what other bug can cause this? where does the arthritis usually occur?
reiters; chlyamydia (with NGU as well); achilles tendon peritonitis
what does a lupus patient present with constitutionally? CV? pulm? renal?
fever, fatigue, weight loss; nonbacterial verrucous endocarditis or pericarditis and Raynauds; hilar adenopathy, pleuritis; nephritic wire loop lesions
what lab tests show false syphilis infection in systemic Lupus erythematous?
false positives with RPR/VDRL d/t antiphospholipid bodies which cross react with cardiolipin
what lab tests are used for screening SLE? diagnosis? drug induced lupus? which cross the placenta?
ANA (antinuclear antibodies); Anti dsDNA (poor prognosis) and Anti Smith antibodies (anti-Sm); anti-histone Abs; Anti SSA (Ro) Abs; serum complement usually low (d/t type III complement activation)
what are smith proteins?
acidic nonhistone proteins bound to RNA
what are the dermatologic manifestations of SLE? MSK?
photosensitivity, malar rash, discoid rash (d/t immunocomplex deposition along basement membrane causing liquefactive degeneration), mucositis (oropharyngeal ulcers); arthritis (small joints- absence of joint deformation- not RA)
what are the hematologic disorders of SLE?
antibodies to leukocytes and RBCs causes: AIHA, thrombocytopenia, leukopenia, Anti PL syndrome (which predisposes to placental complications)
other than placental complications what else do Anti PL antibodies in SLE predispose to?
what are three main drug inducers of drug induced SLE? what are the main Abs? what are
other drugs? what do all these drugs have in common>
procainamide, hydralazine, isoniazid; anti histone Abs; methyldooa, minocycline, penicillamine, dilitazem, chlorporazine; they induce SLE in slow metabolizers of
what is the primary organ of target in sarcoidosis? what are the main elevated serum levels? what is the main histology? what is the mc patient it effects?
lung; ACE levels; multisystem immune mediated noncaseating granulomas (CD4 Th cells interact with unknown agent which then releases cytokines and causes granulomatous formation); young AA female
what is the mcc of noninfectious granulomas in the liver? lung?
what is the lung presentation of sarcoid? dermatologic? what is the histology of the dermatologic lesions?
restrictive lung disease, bilateral hilar lymphadenoapathy, mulitple parenchymal infiltrates( ;
erythema nodosum (painful, usually on lower extremities and usually inflammation of subcutaneous fat),
epithelial granulomas that create nodular lesions that contain microscope Schaumann and asteroid bodies
what is the MSK presentation of sarcoid? what are the lab values in sarcoidosis?
RA; ace levels increased and hypercalcemia
what are schaumann and asteroid bodies? and where are they seen?
laminated calcium concretions and stellate inclusions; in epithelial granulomas in sarcoid
what causes the hypercalcemia in sarcoid? what other disease (think cancer) have the same mechanism?
1 alpha hydroxylase activation in epitheliod macrophages by IFN gamma in granulomatous diseases; hodgkins lymphoma
what is the treatment of sarcoid?
steroids- TNF alpha inhibitors!
what would cause increased levels of amylase in a patient with dypnea and vision problems? what else can cause this and is also see in in this same disease?
sarcoid- uveoparotitis; gammaglobulinemia
what is the main presentation of polymyalgia rheumatica? what is it associated with? what is the typical patient?
pain and stiffness in shoulders and hips with fever, malaise, weight loss; temporal (giant cell) arteritis; >50 y/o
T/F polymyalgia rheumatica can present as muscle weakness and increased CK
what are the lab values in polymyalgia rheumatica? how do you treat it?
increased ESR; prednisone
what diseases should you think about with proximal muscle weakness but normal reflexes?
what are two common myositis'? what is the pathogenesis of each?
polymyositis and dermatomyositis; CD8 T cell induced injury of myofibers, Ab mediated
what do you see on histology of the myositises?
perifascicular inflammation and endomysial inflammation
what are the lab findings in the myositis? and the treatment?
increases CK, increased aldolase, positive ANA, and Anti Jo-1; steroids
T/F myositis have positive Anti DsDNA
false- positive ANA
what is the dermatic presentation of dermatomyositis ? what does it predispose to that polymyositis does not?
malar rash, heliotrope rash, "shawl and face" rash, Gottron's papules, "mechanics" hands; malignancy (lung cancer)
what is a heliotrope rash and what do you see
it in? Gottrons papules?
purple eyelid discoloration (racoons eyes)-dermatomyositis; purple papules on knuckles- dermatomyositis
what two diseases present similarly and are both d/t decreased signal transmission at the NM jxn? how do you distinguish them clinically? diagnosis distinction?
Myasthenia Gravis and Lambert Eaton syndrome; MG usually affects extraocular muscles first and LE usually
proximal muscles first and MG gets worse with use while LE gets better with use; MG symptoms reverse with edrophonium (AchE inhibitor) while LE does not- Tensilon test and nerve stimulation tests causes decremental response in MG and incremental response in LE
what is the pathophysiology of MG? LE? which is more common?
Autoantibodies to postsynaptic AchR; Autoantibodies to presynaptic Ca2+ channels results in decreased Ach release; MG
what is MG associated with? LE?
risk of thymoma ; previous malignacy and this is presenting as paraneoplastic disease (small cell lung cancer)
other than diagnosis , what else is the Tensilon test used for?
distinguishing between exacerbation of MG disease or pharmacologic overdose
what are the extraocular weakness presentations in MG?
diplopia, ptosis (also general weakness)
what is the pathogenesis of scleroderma?
either T cell cytokine stimulation of collagen production of Ab mediated PDGF activation
what is the pathophysiology of scleroderma or progressive systemic sclerosis?
excessive interstitial and perivascular fibrosis and collagen deposition throughout the body as a result of chronic inflammation d/t autoimmunity of small bv
what organ is the mc affected in Scleroderma?how does this present?
skin; puffy and taut skin with absence of wrinkles and tightened facial features (pursed lips also causes skin atrophy (dystrophic calcification) and parchment like skin- also digital vasculitis
what is the mcc of death in scleroderma? what other organs are involved?
respiratory failure d/t interstitial fibrosis and pulmonary Hypertension; renal (hyperplastic arteriosclerosis), heart, muscles, GI
what is the typical patient in Scleroderma? what are the two types? what are the distinguishing serum Abs between the two?
female (75%!); diffuse scleroderma and CREST syndrome; anti Scl-70 -DNA topoisomerase I antibody; anti Centromere antibody
what are the features of diffuse scleroderma that are not in CREST?
widespread skin involvement, rapid progression and early visceral involvement
what does CREST stand for? what is the skin inolvement?
S- Sclerodactyly (tapered claw like fingers)
limited skin involvement (often to just face and fingers)
what does the GI involvement of scleroderma involve?
LES displaced by collage (dysphagia and reflux) and SB
malabsorption d/t loss of villi- also causes wide mouthed diverticuli
what is the treatment of Scerloderma?