MSK Random Facts Flashcards
Baker cyst
Popliteal fluid collection commonly related to chronic joint disease
Most commonly involved ligament in an ankle sprain
Anterior talofibular
What innervates the teres minor?
Ancillary nerve
Injury classically seen in cyclists
Guyon canal injury to ulnar nerve
What supplies sensation to the lateral forearm?
Musculocutaneous nerve (C5-7)
What can you get with a superficial laceration of the Palm?
Injury to the recurrent branch of the median nerve, loss of thenar muscle group, no loss of sensation
Klumpke palsy
Lower trunk damage (C8-T1), loss of the intrinsic muscles of the hand, total claw hand-lumbricals normally flex MCP joints and extend DIP and PIP joints
Thoracic outlet syndrome
Compression of lower trunk and subclavian vessels
What do the interossei do
Dorsal interossei-abduct the fingers, Palmer interossei- adduct the fingers
What can cause an inferior gluteal nerve injury?
Posterior hip dislocation, nerve is L5-S1
What’s in the anterior compartment?
Anterior tibial artery and deep peroneal nerve
What occurs during the power stroke?
Myosin releases bound ADP and PO4 causing displacement of the myosin and actin filament
What is ATP used for in the muscle contraction?
Myosin releasing actin
What is a type 1 muse fiber?
Slow twitch, red fiber, increased mitochondria and myoglobin concentration, used for sustained contraction
What is a type 2 muscle fiber?
Fast twitch fiber, white fiber, more anaerobic glycolysis, weight training results in hypertrophic of fast-twitch muscle fibers
McMurray test
External rotation and extension causing pain->medial meniscal tear; internal rotation and extension->lateral meniscal tear
How is contraction stimulated in smooth muscle?
AP opens L-type voltage gated Ca channel-> increased Ca in the cell binds to calmodulin-> Ca-calmodulin complex enhances myosin-light chain kinase, which phosphorylates myosin and leads to contraction
What do osteoblasts come from?
Differentiate from mesenchymal stem cells in the periosteum
What do osteoclasts come from and how do they work?
Differentiate from monocytes, macrophages. Multinucleated cells that dissolve bone by secreting acid and collagenases
Estrogens effects on bone
Estrogen inhibits apoptosis in bone-forming osteoblasts and induces apoptosis in bone-resorbing osteoclasts
Genetics of achondroplasia
Autosomal dominant (but >85% are sporadic), constitutive activation of fibroblast growth factor receptor (FGFR3) inhibits chondrocyte proliferation
Osteoporosis histo and labs
Trabecular (spongy) bone loses mass and interconnections despite NORMAL mineralization and lab values
What is denosumab?
Monoclonal antibody against RANK-L
MOA of osteopetrosis
Mutations (eg, carbonic anhydrase II) impair ability of osteoclast to generate acidic environment necessary for bone resorption. Leads to thickened, dense bones that are prone to fracture. Pancytopenia and extramedullary hematopoeisis
What’s wrong in rickets/osteomalacia?
Defective mineralization/calcification of osteoid
Lab values in rickets
Low vit D, low Ca, high PTH, low phos
Lab values in Pagets
Normal Ca, phos, and PTH. Elevated ALP.
Histo of pagets
Mosaic pattern of woven and lamellar bone
What are rheumatoid nodules
Fibrinous necrosis
“Soap bubble appearance”
Giant cell tumor. Epiphyseal end of long bones. Locally aggressive benign tumor
Osteochondroma
Mature bone with a cartilagenous cap
Codman triangle
Osteosarcoma
Sunburst pattern
Osteosarcoma
Predisposing factors for osteosarcoma
Paget disease, bone infarcts, radiation, familial retinoblastoma, Li-Fraumenti syndrome (germline p53 mutation)
Where does an osteosarcoma most commonly occur?
Metaphysis of long bones, often around the knee
Onion skin periosteal reaction
Ewing sarcoma
Genetics of Ewing srcoma
t(11;22) translocation causing fusion protein EWS-FLI 1
Where does Ewing sarcoma occur?
Diaphysis of long bones
Histology of Ewing sarcoma?
Anapestic small blue cell malignant tumor
What do you see with osteoid osteomas?
Nighttime pain, central nidus, in the diaphysis
Antibodies in Sjogrens
SS-A (anti-Ro) and/or SS-B (anti-La)
Complications of Sjogrens
Dental caries, mucosa-associated lymphoid tissue (MALT) lymphoma (may present as parotid enlargement)
What drugs can precipitate a gout attack
Niacin, hydrochlorothiazide, cyclosporine, and pyrazinamide
What are the crystals in pseudo gout?
Calcium pyrophosphate
How do you monitor disease progression in anklyosing spondylitis?
Chest expansion
What do you see with ankylosing spondylitis?
Ankylosis, uveitis, aortic regurgitation
Triad of reactive arthritis
Conjunctivits, arthritis, urethritis (post-GI: shigella, salmonella, yersinia, campylobacter or chlamydia infections)
What dermal findings might you see in reactive arthritis?
Keratoderma blennorrhagicum (hyperkeratotic vesicles on the palms and soles) or circinate balanitis (serpiginous annular dermatitis of the glans penis)
What causes lupus nephritis?
Type III hypersensitivity reaction (nephritic: diffuse proliferative glomerulonephritis; nephrotic: membranous glomerulonephritis)
What causes the cytopenia in lupus?
Type II hypersensitivity reaction
Drugs indicated for drug-induced lupus
Procainamide, hydralazine, isoniazid, minocycline, TNF-alpha inhibitors
Which patients may be more likely to get drug-induced lupus?
Slow acetylators
What would you see in labs in sarcoid
Elevated ACE levels, elevated CD4/CD8 ratio
What causes the hypercalcemia in sarcoid
Increased 1-alpha-hydroxylase-mediated vitamin D activation in macrophages
What might you see in acute sarcoid?
Fever, parotid enlargement, anterior uveitis, and facial nerve palsy (Heerfordt-Waldenstrom syndrome)
Antibodies in polymyositis/dermatomyositis
anti-Jo-1 (anti-histidyl-tRNA synthetase), anti-SRP, anti-Mi-2 antibodies
What causes the inflammation in polymyositis and dermatomyositis?
Poly- endomysial inflammation with CD8 cells. Dermato-perimysial inflammation with CD4 cells
What is myositis ossificans?
Metaplasia of skeletal muscle into bone following muscular trauma
Zonula occludens
Tight junction, composed of claudins and occludins
Zonula adherens
Adherents junction, forms belt connecting actin cytoskeletons of adjacent cells with CADherins (Ca dependent adhesion proteins). Loss of E-cadherin promotes metastasis
Macula adherins
Desmosome- structural support via keratin interactions
What is spongiosis
Epidermal accumulation of edematous fluid in intercellular spaces, seen in eczematous dermatitis
What is acantholysis?
Separation of epidermal cells, seen in pemphigus vulgaris
What causes lack of pigment in albinism vs vitiligo?
Albinism- normal melanocyte number with decreased melanin production due to decreased tyrosinase activity or defective tyrosine transport. Can also be caused by failure of neural crest cell migration during development. Vitiligo is due to autoimmune destruction of melanocytes
Merocrine glands
Cells secrete via exocytosis. Ex. salivary, eccrine sweat, apocrine sweat
Apocrine glands
Cells secrete via membrane-bound vesicles. Ex. mammary glands
Holocrine glands
Cell lysis releases entire contents of the cytoplasm and cell membrane. Ex. sebaceous glands, meibomian glands
What is rhinopehyma?
Bulbous deformation of the nose from chronic inflammatory changes in rosacea
Difference between cellulitis and erysipelas?
Cellulitis is an infection of the deeper dermis and subcutaneous tissues (usually s. pyogenes or s. aureus), erysipelas is an infection involving upper dermis and superficial lymphatics (usually s. pyogenes)
Staphylococcal scaled skin syndrome
Exotoxin destroys keratinocyte attachements in stratum granulosum only (vs TEN which destroys dermal-epidermal junction)
Erythema migrans vs. multiforme vs. nodosum
Migrans- lyme; multiforme- dusky circles (often HSV but can be others); nodosum- subcutaneous nodules (sarcoid, coccidioidomycosis, hystoplasmosis, TB, strep, leprosy, Crohn)
Sawtooth infiltrate of lymphocytes at dermal-epidermal junction
Lichen planus
What is lichen planus associated with?
Hep C
Which UV light is dominant in sunburn
UVB (UVA dominant in tanning and photoaging)
What is melanoma often driven by?
Activation mutation in BRAF kinase. Patients with BRAF V600E mutation may benefit from vemurafenib, a BRAF kinase inhibitor)
Which COX is platelet function dependent on?
COX-1 (produces TXA2)
MOA of bisphosphonates
Pyrophosphate analogs; binds hyroxyapatite in bone, inhibiting osteoclast activity
SE of bisphosphonates
Corrosive esophagitis (patients are advised to take with water and remain upright for 30 min); osteonecrosis of the jaw
MOA of teriparatide
Recombinant PTH analog given subcutaneously daily. Increases osteoblastic activity. Causes increased bone growth compared to antiresorptive therapies
What are topical vitamin D analogs used for?
Psoriasis (bind to and activate the vit D receptor, a nuclear transcription factor that causes inhibition of keratinocyte proliferation and stimulation of keratinocyte differentiation
What drugs have their concentrations increased if administered with allopurinol?
Azathioprine and 6-MP
MOA of Febuxostat
Inhibits xanthine oxidase
MOA of Pegloticase
Recombinant uricase that catalyze metabolism of uric acid to allantoin (a more water soluble product)
MOA of probenecid
Inhibits reabsorption of uric acid in proximal convoluted tubule (also inhibits secretion of penicillin)
What should you not give in an acute gout attack?
Salicylates. All but the highest doses depress uric acid clearance
Wickham striae (reticular white lines)
Mucosal involvement of lichen planus
