Bone, Joint & Muscle Pathology Flashcards
What is Achondroplasia?
- Failure of longitudinal bone growth (endochonrdal ossification)→ short limbs
- Membranous ossification is not affected→ large head & chest relative to limbs
- Common cause of dwarfism
- Normal life span & fertility
**Growth Factor involved in Achondroplaisa **
Constitutive activation of fibroblast GF receptor (FGFR3) acutally inhibits chondrocyte proliferation
Pattern of Inheritance of Achondroplaisa
- AD inheritance
- 85% occur sporadically & assoc w/ advanced paternal age
What is Osteoporosis?
Trabecular (spongy) bone loses mass & interconnections despite normal bone mineralization & lab values ( serum Ca2+ & PO43-)
What is Type I Osteoporosis?
- Postmenopausal: inc bone resportion d/t dec estrogen levels
- Femoral neck fracture, distal radius (Colles’) fractures
What is Type II Osteoporosis?
- Senile osteoporosis
- Affects men & women >70 years of age
Prophylaxis for Type II Osteoporosis
- Regular wt bearing exercise
- Sdequate Ca & Vit D intake throughout adulthood
Tx for Osteoporosis Type II
- Estrogen (SERMs) &/or calcitonin
- Bisphosphonates (induce osteoclast apoptosis)
- Pulsatile PTH for severe cases
- Glucocorticoids are contraindicated
What is Osteopetrosis?
Failure of normal bone resorption d/t defective osteoclasts→ thickened, dense bones that are prone to fracture
What does Osteopetrosis look like?
Bone fills marrow space, causing pancytopenia, extramedullary hematopoiesis
What mutations are involved w/ Osteopetrosis?
Carbonic anyhydrase II→ loss of the acidic microenvironment required for bone resorption
Look of Osteopetrosis on X-ray
Bone-in-bone appearance
What are the clinical features of Osteopetrosis?
- Bone fractures
- Anemia, thrombocytopenia & leukopenia w/ extramedullar hematopoiesis
- Hydrocephalus d/t narrowing of foramen magneum
- Renal tubular acidosis
- Cranial nerve impingement→ vision & hearing impairment
Tx for Osteopetrosis
BM transplant is potentialy curative as osteoclasts are derived from monocytes
What can Vit D deficiency cause?
- Rickets in children
- Osteomalacia in adults
Pathway of Vit D Deficiency
- dec Vit D→ dec serum Ca→ Inc PTH secretion → dec serum phosphate
- Hyperactivity of osteoclasts→ inc alk phos
- Defective mineralization/ calcification of osteoid→ soft bones that bow out
What is Paget dz of bone (Osteitis deformans)?
Common, localized disorder of bone remodeling caused by an imbalance in osteoblastic & osteoclastic activity
Lab Values of Osteitis deformans
Normal serum Ca, P & PTH levels w/ inc ALP
What does osteitis deformans look like?
- Mosaic (“woven”) bone pattern
- Long bone chalk-stick fractures
What can Osteitis deformans cause?
- Inc blood flow from inc arteriovenous shunts may cause high-output HF
- Inc risk of osteosarcoma
- Hat size can be Inc
- Hearing loss is common d/t auditory foramen narrowing
- Bone pain
- Lion-like face
What is osteitis fibrosa cystica?
- “Brown tumors” of hyperparathyroidism
- Inc serum Ca, ALP, PTH & dec P
What is Polyostotic fibrous dysplasia?
Bone replaced by fibroblasts, collagen & irregular bony trabeculae
What is McCune-Albright Syndrome?
Form of polycystic fibrous dysplasia char by mulitple unilateral bone lesions assoc w/ endocrine ABN (precocious puberty) & café-au-lait spots
What are the 1º benign bone tumors?
- Giant cell tumor (osteoclastoma)
- Osteochondroma (exostosis)
What age group osteoclastoma occur?
20-40yo
What is Giant Cell tumor?
Locally aggressive benign tumor that arises in the epiphysis of long bones, us. the distal femur or proximal tibial region (knee)
What is the appearance of Giant Cell tumor on X-ray?
“Double bubble” or “soap bubble”
Histo of Giant cell tumor
Spindle-shaped cells w/ multinucleated giant cells & stromal cells
Who does Osteochonroma occur in?
Males <25yo
What is Osteochondroma?
- Most common benign tumor
- Mature bone w/ cartilagenous cap
Where does Osteochondroma commonly originate?
Arise from a lateral projection of the growth plate (metaphysis); bone is continous w/ marrow space
What does Osteochondroma transform to?
Rare transformation to chondrosarcoma
What are the 1° malignant bone tumors?
- Osteosarcoma (osteogenic sarcoma)
- Ewing’s sacroma
- Chondrosarcoma
Who gets Osteosacroma?
- Males> females
- 10-20 yo
What are the predisposing factors to Osteosarcoma?
- Paget’s dz of bone
- Bone infarcts
- Radiation
- Familial retinoblastoma
Characteristics of Osteosarcoma
- Metaphysis of long bones, often around distal femur, proximal tibial region (knee)
- Codman’s triangle (from elevation of periosteum or ‘sunburst pattern’ on X-ray
Tx of Osteosarcoma
Aggressive, tx w/ surgical en bloc resection (w/ limb salvage) & chemotherapy
Who gets Ewing’s Sarcoma?
Boys <15yo
Where does Ewing’s Sarcoma occur?
Commonly appears in diaphysis of long bones, pelvis, scapula & ribs
Histo of Ewing’s Sarcoma
- Anaplastic small blue cells that resemble lymphocytes
- “Onion skin” appearance on X-ray
Prognosis of Ewing’s Sarcoma
Extremely aggressive w/ early mets but responsive to chemo
What translocation is Ewing’s Sacroma assoc w/?
t(11;22) translocation
(11+22=33 Patrick Ewing’s jersey #)
Who gets Chonrosarcoma?
Men 30-60yo
Where is Chondrosarcoma located?
Pelvis, spine, scapula, humerus, tibia or femur
What is Chondrosarcoma?
- Malignant cartilaginous tumor
- May be of 1° origin or from osteochondroma
- Expansile glistening mass w/in the medullary cavity
Cause of Osteoarthritis
Mechanical- joint wear & tear destroys articular cartilage
Joint findings of Osteoarthritis
- Subchondral cysts
- Sclerosis
- Osteophytes (bone spurs)
- Eburnation (polished ivory-like appearance of bone)
- Bouchard’s nodes (PIP)
- Heberden nodes (DIP)
- No MCP involvement
Predisposing factors of Osteoarthritis
- Age (>60yo) major RF
- Obesity
- Joint deformity
- Trauma
Clinical Presentation of Osteoarthritis
- Joint stiffness in the morning that worsens during the day & improves w/ rest
- Knee CT loss begins medially (“bowlegged”)
- Noninflammatory
- No systemic sx
Tx of Osteoarthritis
NSAIDs & Intra-articular glucocorticoids
Cause of Rheumatoid arthritis
- Autoimmune- inflammatory destruction of synovial joints
- Type III hypersensitivity
- IgM auto-Ab against Fc portion of IgG (rheumatoid factor)
Joint findings in RA
- Synovitius→ Pannus (inflam granulation tissue)
- Rheumatoid nodules: central zone of necrosis surrounded by epi histiocytes
- Radial deviation of wrists
- Ulnar deviation of fingers
- Boutonniere deformity of thumb
- Baker’s cysts (in politeal fossa)
- No DIP involvement*
- Swan-neck deformity of fingers
Predisposing Factors of RA
- Classically women of childbearing age
- 80% have + Rheumatoid factors (anti-IgG Ab)
- Anti-cyclic citrullinated peptide Ab is more specific
- Strong assoc w/ HLA-DR4**
Clinical Presentation of RA
- Morning stiffness lasting >30 min & improving w/ use
- Symmetric joint involvement
- Systemic sx- fever, fatigue, pleuritis, pericarditis, vasculitis, lymphadenopathy, interstitial lung fibrosis
Tx of RA
- NSAIDs
- Glucocorticoids
- Dz-modifying agents (methotrexate, sulfasalazine, TNF-alpha inhibitors)
What is Sjögren’s Syndrome?
Lymphocytic infiltration of exocrine glands, especially lacrimal & salivary
Classic Triad of Sjögren’s Syndrome
- Xerophthalamia- dry eyes, conjuctivitis, “sand in my eyes”
- Xerostomia- dry mouth, dysphagia
- Arthritis
Characteristics of Sjögren’s Syndrome
- Parotid enlargement
- inc risk of B-cell lymphoma
- Dental Caries
- Auto-Ab to ribonucleoprotein Ag: SS-A (Ro), SS-B (La)
- Assoc w/ rehumatoid arthritis
What is Gout?
Precipitation of monosodium urate crystals into joints d/t hyperuricemia from overy production or dec excretion of uric acid
What does Gout look like?
Crystals are needle shaped & negatively birefringemant= yellow crystals under parallel light
Sx of Gout
- Asymmetric joint distribution
- Joint is swollen, red & painful
- Classic manifestation is painful MTP joint of the big toe (podagra)
- Tophus formation (often on external ear, olecranon bursa or Achilles tendon)
- Acute attack tends to occur after a large meal or alcohol consumption (alcohol metabolites compete for same excretion sites in kindney as uric acid, causing dec uric acid sec & subsequent bulidup in blood)
Tx of Gout
- Acute: NSAIDs (indomethacin), glucocorticoids
- Chronic: xanthine oxidase inhibitors (allopurinol, febuxostat)
Cause of Pseudogout
- Depostions of Ca pyrophosphate dihydrate (CPPD) crystals w/in the joint space
- Usuallly affects large joints (classically the knee)
What does Pseudogout look like?
- Forms basophilic, rhomoid crystals that are weakly + birefringement
- Crystals are blue when parallel to the light