USMLE (Fach) / Musculoskeletal, Skin, and Connective Tissue (Lektion)
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- Systemic lupus erythematosus Systemic, remitting, and relapsing autoimmune disease. Organ damage primarily due to type III hypersensitivity reaction and, to a lesser degree, a type II hypersensitivity reaction. Associated with deficiency ...
- Drugs known for causing a lupus-like syndrome - procainamide (antirhythmic agent Ia) - quinidine (antirhythmic agent Ia) - hydralazine (muscle relaxant)
- Scleroderma (systemic sclerosis) Triad of autoimmunity, noninflammatory vasculopathy, and collagen desposition with fibrosis.- Commonly sclerosis of skin, manifesting as puffy, taut skin without wrinkles, fingertip pitting. - Can involve ...
- Osteoarthritis Degeneration of articular cartilage. Chondrocytes mediate degradation and inadequate repair. Predisposing factors: Age, female, obesity, joint trauma Presentation: Pain in weight-bearing joints after ...
- Rheumatoid arthritis Autoimmune – inflammation induces formation of pannus (proliferative granulation tissue), which erodes articular cartilage and bone. Predisposing factors: Female, HLA-DR4, smoking, (+) rheumatoid ...
- Ankylosing spondylitis Seronegative spondyloarthritis. Symmetric involvement of spine and sacroiliac joints → ankylosis (joint fusion), uveitis, aortic regurgitation.- Arthritis without rheumatoid factor. - Strongly associated ...
- Reiter's syndrome - spondyloarthropathy - characterized by the triad of1. Arthritis2. Urethritis3. Conjunctivitis - associated with HLA-B27
- Gower's sign indicates weakness of the proximal muscles, namely those of the lower limb - describes a patient that has to use their hands and arms to "walk" up their own body from a squatting position due to lack ...
- Duchenne's muscular dystrophy - 2/3 X-linked recessive; 1/3 secondary spontaneous mutation in dystrophin gene - pseudohypertrophy of the calf muscles - positive Gower's sign (proximal muscle weakness)
- Myotonic dystrophy - autosomal dominant - expansion of trinucleotide repeat sequence in region of the myotonin protein kinase gene --> amplification phenomenon - generalized muscle weakness - when patient shakes hand, ...
- Sciatica - pain distributed in the area that the sciatic nerve innervates - arises from L4-S3 - If L4-L5 disk is herniated, symptoms reflect the distribution of the L5 dermatome, because the L5 nerve root descends ...
- Gout Acute inflammatory monoarthritis caused by precipitation of monosodium urate crystals in joints.- Risk factors: male sex, hypertension, obesity, diabetes, dyslipidemia, hyperuricemia. Strongest ...
- Lesch-Nyhan syndrome - deficiency of the enzyme hypoxanthine-guanine phosphoribosyl transferase (HGPRT)--> purines are not reused but instead degraded into uric acid - X-linked recessive - central nervous system symtoms, ...
- Uric acid production - hypoglycemia increases uric acid production by reducing cellular ATP production --> increased levels of cellular adenosine --> substrate for purine catabolism - alcohol is believed to exacerbate gout ...
- Treatment of an acute gout attack 1. Colchicine- inhibits microtubule polymerization and so prevents phagocytosis of uric acid crystals by macrophages/neutrophils (phagocytosis elicits the inflammatory response)- used cautiously because ...
- Fibromyalgia Rheumatologic disorder characterized by widespread musculoskeletal pain associated with "tender points," stiffness, paresthesias, poor sleep, fatigue, cognitive disturbance.- Most common in women 20-50 ...
- Polymyositis/dermatomyositis - ↑ CK, ⊕ ANA (nonspecific), ⊕ anti-Jo-1 (histidyl-tRNA synthetase, specific), ⊕ anti-SRP (specific), ⊕ anti-Mi-2 (specific) antibodies.- Both disorders associated with interstitial lung ...
- Osteopetrosis Failure of normal bone resorption due to defective osteoclasts → thickened, dense bones that are prone to fracture. Persistence of primary spongiosa in the medullary canal.- Mutations (eg, carbonic ...
- Achondroplasia Failure of longitudinal bone growth (endochondral ossification) → short limbs. - Large head relative to limbs. - Constitutive activation of fibroblast growth factor receptor (FGFR3) actually inhibits ...
- Paget disease of bone (osteitis deformans) Common, localized disorder of bone remodeling caused by ↑ osteoclastic activity followed by ↑ osteoblastic activity that forms poor-quality bone. - Serum Ca2+, phosphorus and PTH levels are normal. - ...
- Osteogenesis imperfecta - genetic defects in type I collagen weaken bone
- Osteomalacia/rickets Defective mineralization of osteoid (osteomalacia) or cartilaginous growth plates (rickets, only in children).- Most commonly due to vitamin D deficiency. - X-rays show osteopenia and "Looser zones" (pseudofractures) ...
- Wegener's granulomatosis - vasculitis with necrotizing granulomas in the lung and necrotizing glomerulonephritis - hemoptysis (blood-tinged sputum), hematuria - c-ANCA positive - chest x-ray: bilateral nodular and cavitary ...
- Kawasaki syndrome - inflammation of middle-sized blood vessles - mucocutaneous lymph node syndrome - mostly in children < 5 years - mucosal inflammation- cutaneous maculopapular rash- lymph node enlargement- unexplained ...
- Polyarteritis nodosa - inflammation of tunica media of medium-sized muscular arteries (renal, visceral vessles) - fever, myalgia, fatigue, abdominal pain - 30% associated with hepatitis B virus (HbsAg-positive) - multiple ...
- Henoch-Schönlein purpura - IgA vasculitis - maculopapular petechial rash on buttocks/lower extremities - glomerulonephritis (--> hematuria) - abdominal pain, melena - most common systemic vasculitis in children
- Thromboangiitis obliterans = Bürger's disease - inflammatory occlusive disease of the arteries of the distal extremities - male smokers under the age of 40 - distal extremity cold intolerance Treatment: quit smoking
- Takayasu arteritis - "pulseless disease" - granulomatous thickening of aortic arch - elevated ESR - primarily affects Asian females < 40 year old - different blood pressures in the arms, weak pulses in upper extremity- femoral ...
- "Unhappy triad" 1. medial collateral ligament (MCL) 2. medial meniscus 3. anterior cruciate ligament (ACL) - positive anterior drawer sign --> tearing of the ACL- abnormal passive abduction --> torn MCL
- Osteitis fibrosa cystica - caused by hyperparathyroidism - characterized by "brown tumors" (cystic spaces lined by osteoclasts, filled with fibrous stroma) - high serum calcium, low serum phosphorus, high alkaline phosphatase
- Polymyalgia rheumatica Pain and stiffness in proximal muscles (eg, shoulders and hips), often with fever, malaise, weight loss.- Does not cause muscular weakness.- More common in women >50 years of age- Associated with temporal ...
- Sjögren syndrome Autoimmune disorder characterized by destruction of exocrine glands (especially lacrimal and salivary) by lymphocytic infiltrates.- Predominantly affects women 40-60 years old. Findings:- Inflammatory ...
- Pseudogout - deposition of calcium pyrophosphate crystals within the synovia - basophilic, rhomboid crystals that are positively birefringent (as opposed to negatively birefringent, needle-shaped crystals in gout) ...
- Sarcoidosis Immune-mediated, widespread noncaseating granulomas, elevated ACE levels, and elevated CD4/CD8 ratio in bronchoalveolar lavage fluid. - More common in African-American females - Often asymtomatic except ...
- Osteoid osteoma - Adults <25 years old.- Males > females. Location: Cortex of long bones Characteristics: - Presents as bone pain (worse at night) that is relieved by NSAIDs.- Bony mass (<2 cm) with radiolucent osteoid ...
- Osteosarcoma Most common 1° malignant tumor of bone. - Accounts for 20% of 1° bone cancers.- Peak incidence of 1° tumor in males <20 years.- Less common in elderly; usually 2° to predisposing factors, such as ...
- Temporal arteritis (giant cell arteritis) - affects medium and small arteries (usually carotid artery) - focal, granulomatous - unilateral headache, jaw claudication, impaired vision (occlusion of ophthalmic artery, which can lead to blindness) ...
- Child abuse - metaphyseal corner fractures - posterior rib fractures - abnormal bruising - retinal dislocations or hemorrhages
- Erythema nodosum Inflammation of subcutaneous fat - often accompanied by fever and malaise Occurance:- inflammatory-bowel diseases (Crohn disease, ulcerative colitis)- sarcoidosis- drugs (oral contraceptives, sulfonamides)- ...
- Colles' fracture Complete transverse fracture of the distal radius - most commonly in the elderly after forced dorsiflexion - avulsion of the styloid process from the shaft of the radius - "dinner fork" deformity
- Osteonecrosis (avascular necrosis) Infarction of bone and marrow, usually very painful.- Most common site is femoral head (due to insufficiency of medial circumflex femoral artery [posterior]). Causes:- Corticosteroids- Alcoholism- Sickle ...
- Lab values in bone disorders Osteoporosis: - Calcium, - phosphate, - ALP, - PTH - ↓ bone mass Osteopetrosis: -/↓ Calcium, - phosphate, - ALP, - PTH - Dense, brittle bones- Ca2+ ↓ in severe, malignant disease Paget disease ...
- Calcium pyrophosphate deposition disease (pseudogout) ... Deposition of calcium pyrophosphate crystals within the joint space.- Occurs in patients >50 years old- Both sexes affected equally - Usually idiopathic, sometimes associated with hemochromatosis, hyperparathyroidism, ...
- Septic arthritis S aureus, Streptococcus, and Neisseria gonorrhoeae are common causes. - Affected joint is swollen, red, and painful.- Synovial fluid purulent (WBC >50,000/mm3). Gonococcal arthritis – STI that presents ...
- Seronegative spondyloarthritis Arthritis without rheumatoid factor (no anti-IgG antibody). Strong association with HLA-B27 (MHC class I serotype). Subtypes share variable occurence of inflammatory back pain (associated with morning ...
- Myasthenia gravis Most common neuromuscular junction disease. - Autoantibodies to postsynaptic ACh receptor - Ptosis, diplopia, weakness. Worsens with muscle use. - Improvement after edrophonium (tensilon) test - Associated ...
- Lambert-Eaton myasthenic syndrome Autoantibodies to presynaptic Ca2+ channel → ↓ ACh release - Proximal muscle weakness, autonomic symptoms (dry mouth, impotence)- Improves with muscle use - Associated with small cell lung cancer
- Raynaud phenomenon ↓ blood flow to skin due to arteriolar (small vessel) vasospasm in response to cold or stress: color change from white (ischemia) to blue (hypoxia) to red (reperfusion).- Most often in the fingers ...
- Types of muscle fibers Type 1 muscle:- Slow twitch: red fibers resulting from ↑ mitochondria and myoglobin concentration (↑ oxidative phosphorylation) → sustained contraction- Proportion ↑ after endurance training. ...
- Bone formation Endochondral ossification:- Bones of axial skeleton, appendicular skeleton, and base of skull.- Cartilaginous model of bone is first made by chondrocytes. Osteoblasts and osteoclasts later replace with ...