Musculoskeletal Pathology Flashcards
Achondroplasia
sporatic activating mutation in <b>FGFR3</b> causes impaired cartilage proliferation in growth plate leading to short limbs
Two mechanisms by which bone can form:
- <b>intramembranous</b> (CT matrix)
2. <b>endochondral</b> (cartilage calcifies/dies and bone grows)
Osteogenesis Imperfecta
AD <b>defect in collagen type I synthesis </b> affecting bone formation causing fractures, blue sclera and hearing loss
*<b>blue sclera</b> is due to exposure of choroidal veins from lack of collagen in eye
Osteopetrosis (cause, symptoms, treatment)
<b>carbonic anhydrase II mutation</b>–> lack of acidic environment–> poor osteoclast function (resorption)–> causing abnormally thick bones–> prone to fracturing
- <b>fractures, anemia, thrombocytopenia, leukopenia, vision/hearing impairment (CN compression), hydrocephalus, renal tubular acidosis</b>
- Treatment: <b>bone marrow transplant</b> to enhance ability ot make monocytes/osteoclasts
Rickets/Osteomalacia
defective osteoid mineralization due to vitamin D deficiency
<b>Rickets</b>: in children leading to pigeon breast deformity, frontal bossing, rachitic rosary (joint knobs), bowing of legs
<b>Osteomalacia</b>: in adults leading to fractures (<b>decreased serum Ca2+ and P; increased PTH and alkaline phosphatase</b>)
Osteoporosis (definition, risks, forms, treatment)
loss of <b>trabecular</b> bone mass causing porous bones, pain and fractures (i.e. compression fractures) but serum Ca2+, P, PTH and alkaline phosphatase are normal
- <b>Risks</b>: peak bone mass and rate of bone loss thereafter
- Forms: senile and postmenopausal
*Treatment: <b>bisphosphonates (osteoclast apoptosis)</b>
Paget Disease of Bone/Osteitis Deformans) (definition, features, treatment, complications)
<b>localized</b> osteoclast and osteoblast imbalance (possibly due to paramyxovirus infection of osteoclasts) causing the formation of thick sclerotic bone that fractures easily
- Features: pain, increased hat size, hearing loss, <b>lion like facies, increased alkaline phosphatase</b>
- Treatment: bisphosphonates and calcitonin
- Complications: <b>high output cardiac failure and osteosarcoma</b>
Osteomyelitis (types)
bacterial infection of bone and marrow space that spreads through blood causing by sepsis
- metaphysis in kids; epiphysis in adults
- <b>lytic focus (necrosis) surrounded by sclerosis on xray</b>
- In sickle cell: dysfunctional spleen cannot remove Salmonella from blood
- Tuberculous: targets vertebral column
- Pseudomonas aeruginosa- when foot is punctured
Avascular (Aseptic) Necrosis
ischemic necrosis of bone and marrow due to decreased blood supply from <b>trauma/fracture, steroids, sickle cell (vasoocclusive), or Caisson Disease (fat embolism which occludes microcirculation in bone)</b>
*common site: femoral head and condyle
Osteoma
benign tumor on surface of facial bones
*associated with Gardner Syndrome (polyps in colon)
Osteoid Osteoma
benign tumors of osteoblasts surrounded by <b>rim of reactive bone in cortex of long bones in which pain resolves with aspirin</b>
Osteoid Osteoma vs. Osteoblastoma
<b>Osteoid Osteoma</b>: small tumor, arises in cortex of long bones, pain responds to aspirin
<b>Osteoblastoma</b>: large tumor, arises in vertebrae, does not respond to aspirin
Osteochondroma
lateral projection of growth plate (bone tumor) with cartilage cap
*<b>overlying cartilage can transform to chondrosarcoma</b>
Osteosarcoma (definition and risk factors)
malignant proliferation of osteoblasts that takes off bone periosteum (CT that surrounds bone and helps it form new layers) in <b>metaphysis of distal femur or proximal tibia</b>
*Risk factosr: <b>familial Rb, Paget disease, radiation exposure</b>
Giant Cell Tumor
the only <b>epiphysis bone tumor</b> occurring in distal femur or proximal tibia composed of <b>multinucleated giant cells and stromal cells</b>
*<b>“soap-bubble” appearance on xray</b></b>
Ewing Sarcoma
malignant proliferation of poorly-differentiated cells <b>derived from neuroectoderm in diaphysis of long bones in male children</b>
- <b>“onion skin”</b> appearance on xray
- 11.22 translocation
Cartilage tumors
benign–> <b>Chondroma</b> affecting medulla of small bones in hands and feet
malignant–> <b>Chondrosarcoma</b> affecting medulla in central pelvis and skeleton
Dermatomyositis (definition, labs, treatment)
inflammatory disorder of skin and skeletal muscle causing: weakness <b>heliotrope and malar rashes and red papules on joints</b>
- (<b>derimysial inflammation with CD4+ T-cells and perifasicular atrophy</b>)
- <b>Labs</b>: increased creatinine kinase, + ANA and anti-Jo1 Ab
- Treatment: corticosteroids
Polymyositis
inflammatory disorder of skeletal muscle (<b>endomysial inflammation with CD8+ T-cells and necrotic muscle fibers)</b>
X-Linked Muscular Dystrophy
deletion of dystrophin causes muscle wasting and replacement to fat (often involves myocardium)
*<b>calf pseudohypertrophy and increased creatinine kinase</b>
Adipose tissue tumors
<b>Lipoma</b>: benign
<b>Liposarcoma</b>: malignant; characteristic cell is <b>lipoblast</b>
Skeletal muscle tumors
<b>Rhabdomyoma</b>: benign; cardiac rhabdomyoma is associated with tuberous sclerosis
<b>Rhabdomyosarcoma</b> malignant, desmin + and commonly found in head, neck and vagina; characteristic cell is rhabomyoblast
Solid vs. Synovial Joints
<b>solid</b>- tightly connected for structural strength
<b>synovial</b>- space to allow for motion and contains synovia/hyaluronic acid
Degenerative Joint Disease (definition, what it affects, risk factors)
progressive articular cartilage degeneration affecting <b>hip, lower lumbar spine, knees, DIP and PIP (in fingers)</b> associated with <b>morning stiffness that gets worse</b>
- Risk factors: age, obesity, trauma
- <b>eburnation of subchondral bone and osteophyte formation</b>
What disorders affect the DIP?
<b>Degenerative Joint Disease</b> and <b>Psoriatic Arthritis</b>
Rheumatoid Arthritis (definition, symptoms, joints involve, complications, pannus)
joint space narrowing causing loss of cartilage (PIP, wrists, elbows, knees, ankles) that is chronic, systemic, autoimmune, involves <b>HLA-DR4</b>, and is characterized by <b>morning stiffness that gets worse</b>
- nodules, vasculitis, pleural effusions, LAD, interstitial lung fibrosis, Baker cyst, Swan neck deformity, Boutonniere deformity
- <b>Complications: secondary amyloidosis</b>
<i>pannus forms- granulation tissue within synovial tissue to release cytokines that destroy the articular cartilage </i>
Baker Cyst
swelling of semimembranous or other synovial bursa behind knee joint and occurs in Rheumatoid Arthritis
Seronegative Spondyloarthropathies
<b>lack of rheumatoid factor, HLA-B27 association and involves the axial skeleton</b>
Ankylosing Spondyloarthritis
involves sacroiliac joints and involves vertebral spine eventually leading to its fusion
- occurs primarily in <b>young males</b>
- uveitis (blurry vision) and aortitis (weak wall, aortic regurgitation
Reiter Syndrome (definition, when most likely to occur)
“can’t see, can’t pee, can’t climb a tree”
<b>conjunctivitis, urethritis, arthritis</b>
*in young male adult weeks after GI or C. trachomatis infection
Psoriatic Arthritis
affects axial and peripheral joints (including DIP of hands and feet)
Infectious Arthritis
bacterial infection caused by<b>S. aureus (young adults) or N. gonorrhoeae (older children and adults)</b> leading to a warm, erythematous joint with limited range of motion
*fever, increased WBC, increased ESR (measures inflammation)
Gout (definition, types)
MSU crystal deposition in tissues from hyperuricemia causing <b>yellow needle shaped crystals with negative birefringence</b>
Types:
- <b>Primary</b>: HGPRT deficiency
- <b>Secondary</b>: underexcretion or overproduction of uric acid due to leukemia, Lesch-Nyhan Syndrome, renal insufficiency
- <b>Acute</b>:podagra (painful great toe), triggered by alcohol and red meat consumption
- <b>Chronic</b>: tophi (uric acid crystals in soft tissue of joints), renal failure
HGPRT
salvages HX and guanine to decrease xantine and urinc acid (UA)
Pseudogout
Ca2+ pyrophosphate deposition causing <b>blue rhomboid-shaped crystals with weak positive birefringence</b>
Role of estrogen in maintaining bone mass
it enhances osteoblastic activity and inhibits osteoclastic activity by <b>inhibiting the secretion of cytokines</b> that help in osteoclastogenesis
Osteochondrosis ( & a variant of it)
avascular necrosis of ossification centers (epiphyses) in children
*variant= osteochondritis dissecans (limited to articular epiphysis- commonly the knee)
Osgood-Schlatter disease
swelling of tibial tuberosity that has no effect on bone growth
Fibrous Dysplasia
replacement of medullary bone by fibrous tissue due to defect in osteoblastic differentiation/maturation
Osteoarthritis
progressive degeneration of articular cartilage due to the activation of metalloproteinases by cytokines which degrades its components: proteoglycans (elasticity) and type II collagen (tensile strength)
- reactive bone formation and subchondral cysts
- Heberden nodes (DIP enlargements) and Bouchard nodes (PIP enlargement)
Neuropathic Arthropathy (Charcot Joint)
noninflammatory joint disease that is secondary to a neurologic disease (DM, syringomyelia, tabes dorsalis)
*<b>loss of proprioception and deep pain sensation leading to recurrent trauma</b>
Rheumatoid Factor (RF) ( & what it binds to)
IgM autoantibody that has specificity for the Fc portion of IgG
*RF binds IgG forming immunocomplexes that activate the complement system to produce C5a for neutrophils and leukocytes to enter space
Caplan syndrome
rheumatoid nodules in lung plus pneumoconiosis
Sjogren syndrome
autoimmune destruction of salivary glands and lacrimal glands
*can be seen in Rheumatoid arthritis
L. Septic Arthritis
due to: S. aureus, N. gonorrhoeae or Lyme disease
causes: localized infection, fever/flu-like symptoms, (2/3 proceed to:) early disseminated disease, chronic disease (disabling arthritis)
Type I vs. Type II muscle fibers:
<b>Type I</b>: red, slow twitch, do not fatigue easily, rich in mitochondria, poor in ATPase enzymes
<b>Type II</b>: white, fast twitch, fatigues easily, poor in mitochondria, rich in ATPase enzymes
Trichinella spiralis infection (definition, complications)
causes muscle pain from eating undercooked pork
*complications: myocarditis, encephalitis
