Pathology of MSK non-tumor diseases Flashcards
1
Q
Osteogenesis imperfecta
A
- Pts have long arms relative to legs, multiple fractures in the legs from early life that healed improperly
- They have thin, weak tibias w/ little calcification (abnormal osteoid matrix)
- Usually is dominant (less severe) form
- Pts do not produce normal amount of osteoid so the bones (especially weight-bering ones) are susceptible to fractures
- Can also see blue sclera syndrome
2
Q
Osteomyelitis 1
A
- Irregular lesion w/ sclerosis (encapsulation), suggests benign process
- Histologically see inflammatory cells (PMNs) eroding the bone
- Were recruited there due to an abscess from bacteria (usually staph aureus)
3
Q
Osteomyelitis 2
A
- The bone is not viable, and is called sequestrum: necrotic bone detached from blood supply (looks dark)
- The new bone being formed around the lesion is the involucrum: body’s attempt to make new bone around abscess (is the sclerotic region)
- Looks irregular and w/ pockets of bone formation
- Common complication: chronic suppurative osteomyelitis (draining sinuses btwn infected bone and skin), squamous cell CA and secondary amyloidosis
4
Q
Pagets disease 1
A
- Pts (often men) usually over 40 have pain at site of lesion, w/ markedly elevated serum alk phos levels (w/o having other liver nzs or PTH elevated)
- Bone is thickened and deformed, a mix of sclerosis and lysis
- Can see cement (mosaic) lines: lines btwn resorbed and newly formed bone
5
Q
Pagets disease 2
A
- There is normal calcification but abnormal resorption and production
- Variability in thickness of tabeculae
- Abnormal activity of both osteoclasts and osteoblasts, but osteoblast activity eventually is higher (phase 3), leading to thick bones and increases alk phos
- Phase 1: increased osteoclast activity
- Phase 2: mixed osteoclast and osteoblast activity both increased
- Complications: hemodynamic derrangement (due to hypervascular bone) and secondary osteosarcoma
6
Q
Pott disease (TB infection of vertebrae)
A
- Pts have soft tissue lesions usually in the lower back, and are PPD positive (due to TB), often immunocompromised
- The mass is of lymph nodes and other soft tissue, there are granulomas of cartilaginous disks and collapsed vertebras
- Histologically, the masses contain lymphocytes and plasma cells, zones of degeneration (necrosis), some giant and epithelioid cells
- Positive for acid fast stain (TB), can culture and PCR for Dx
7
Q
RA 1
A
- Chronic process of symmetrical joint destruction, 25% show rheumatoid nodules (subQ nodules on extensor surfaces)
- Joints are warm, tender, edematous, stiff
- There is pannus (fibrous outgrowth/thickening of synovium)
- The rheumatoid nodules show granulomas of chronic inflammation
8
Q
RA 2
A
- Synovial fluid has high abundance of PMNs, which are drawn to the joint by chemokines/complement
- Chemokines released by plasma cells and lymphocytes, which are found in the joint tissue
- These are drawn to the joint due to the immune complexes formed from the RF-IgG complexes that are deposited in the joints (autoimmune) and phagocytosed by synoviocytes
9
Q
Osteoarthritis
A
- Leads to gradually progressive pain and limited range of motion in the affected joints (due to aging), NOT due to inflammation
- There can be deformities of subchondral bones (osteophytes indicating new bone formation), loss of articular cartilage and sclerosis
- The loss/fragmented articular cartilage also can lead to bone resorption
- Fibrocartilage shows uneven distribution of chondrocytes
- There is clefting/fraying and then loss of articular cartilage
- Some areas of thick bone, other areas of weak bone
10
Q
Fibrous dysplasia 1
A
- Circumscribed uneven thinning of bone (ground glass appearance), progressive replacement of a localized area of bone by abnormal proliferation of fibrous tissue
- Middle of lesion is jelly-like substance (fibrous tissue + hemorrhage)
- Histologically there is osteoid getting calcified around edges, bone haphazardly formed but not at the stress lines (not lined by osteoblasts
11
Q
Fibrous dysplasia 2
A
- Non-linear formation of bone, randomly organized into circles and semicircles (woven, not lamellar bone)
- Two types: monostotic (usually on ribs, causing deformities and pain/fracture) and polyostotic (usually affects face, also causing deformity and pain/fractures)
- The Rx is bone grafts
- Not a malignant process
12
Q
Osteoporosis 1
A
- Decrease in total mass of bone with micro-architectural deterioration
- Ratio of mineralized:non-mineralized (osteoid) bone is normal
- Bone loss produces pain and increases chance of fracture
- Due to dysregulation of osteoclast formation/function via RANK pathway
- Very common, especially primary osteoporosis in elderly (resorption outpaces formation)
13
Q
Osteoporosis 2
A
- Secondary osteoporosis: due to immobilization, drugs, malnutrition/absorption, or endocrine d/o
- Affects all bones in body, but pain primarily in weight bearing bones
- Ca, PO, alk phos values generally normal
- Histology: thinned cortical and trabecular bone (changes may be subtle, or very apparent)
14
Q
Osteomalacia
A
- AKA rickets (when in children), structural abnormality of bone caused by defective mineralization of osteoid (osteoid is present in normal or increased amounts but not calcified)
- Due to lack of vit D (deficiency), which is required for mineralization of osteoid
- Rickets can cause deformities of bone and osteopenia, but osteomalacia only causes osteopenia (no deformities)
- Lab values: increased alk phos, decreased Ca, PO
- Histology: trabecular are characterized by peripheral “seams” of uncalcified osteoid
15
Q
Gout 1
A
- Urate crystals are deposited in connective tissue, associated w/ increased uric acid in serum
- Primary: mainly elderly men w/ increased uric acid production, decreased uric acid excretion or both
- Secondary: rapid cell destruction releases uric acid (chemo), and decreased excretion (renal failure)
- Acute gouty arthritis: deposition of sodium urate crystals in synovial membrane
