Musculoskeletal, Skin, and Connective Tissue - Pathology (1) Flashcards
1
Q
Achondroplasia
A
- Failure of longitudinal bone growth (endochondral ossification) –> short limbs.
- Membranous ossification is not affected –> large head relative to limbs.
- Constitutive activation of fibroblast growth factor receptor (FGFR3) actually inhibits chondrocyte proliferation.
- > 85% of mutations occur sporadically and are associated with advanced paternal age, but the condition also demonstrates autosomal dominant inheritance.
- Common cause of dwarfism.
- Normal life span and fertility.
2
Q
Osteoporosis
- Definition
- Type I
- Type II
- Senile osteoporosis
- Prophylaxis
- Treatment
A
- Definition
- Trabecular (spongy) bone loses mass and interconnections despite normal bone mineralization and lab values (serum Ca2+ and PO43-).
- Diagnosis by a bone mineral density test (DEXA) with a T-score of ≤ -2.5.
- Can be caused by long-term exogenous steroid use.
- Can lead to vertebral crush fractures—acute back pain, loss of height, kyphosis.
- Type I
- Postmenopausal
- Increased bone resorption due to decreased estrogen levels.
- Femoral neck fracture, distal radius (Colles) fracture.
- Postmenopausal
- Type II
- Senile osteoporosis
- Affects men and women > 70 years old.
- Prophylaxis
- Regular weight-bearing exercise and adequate calcium and vitamin D intake throughout adulthood.
- Treatment
- Bisphosphonates, PTH, SERMs, rarely calcitonin
- Denosumab (monoclonal antibody against RANKL).
- Senile osteoporosis
3
Q
Osteopetrosis (marble bone disease)
- Definition
- Findings
- Treatment
A
- Definition
- Failure of normal bone resorption due to defective osteoclasts –> thickened, dense bones that are prone to fracture.
- Mutations (e.g., carbonic anhydrase II) impair ability of osteoclast to generate acidic environment necessary for bone resorption.
- Findings
- Bone fills marrow space –> pancytopenia, extramedullary hematopoiesis.
- X-rays show bone-inbone appearance [A].
- Can result in cranial nerve impingement and palsies as a result of narrowed foramina.
- Treatment
- Bone marrow transplant is potentially curative as osteoclasts are derived from monocytes.
4
Q
Osteomalacia/rickets
- Definition
- Caused by…
- Causes…
A
- Definition
- Decreased vitamin D –> decreased serum calcium –> increased PTH secretion –> decreased serum PO43-.
- Caused by…
- Vitamin D deficiency.
- Defective mineralization / calcification of osteoid –> soft bones that bow out.
- Causes…
- Osteomalacia in adults
- Rickets in children.
- Hyperactivity of osteoblasts –> increased ALP (osteoblasts require alkaline environment).
5
Q
Paget disease of bone (osteitis deformans) (420)
- Definition
- Findings
- Stages of Paget disease:
A
- Definition
- Common, localized disorder of bone remodeling caused by increases in both osteoblastic and osteoclastic activity.
- Increased blood flow from increased arteriovenous shunts may cause high-output heart failure.
- Increased risk of osteogenic sarcoma.
- Findings
- Serum Ca2+, phosphorus, and PTH levels are normal.
- Increased ALP.
- Mosaic pattern of woven and lamellar bone [A]
- Long bone chalk-stick fractures.
- Hat size can be increased [B]
- Hearing loss is common due to auditory foramen narrowing.
- Stages of Paget disease:
- Lytic—osteoclasts
- Mixed—osteoclasts + osteoblasts
- Sclerotic—osteoblasts
- Quiescent—minimal osteoclast/osteoblast activity
6
Q
Osteonecrosis (avascular necrosis)
A
- Infarction of bone and marrow, usually very painful.
- Most common site is femoral head (due to insufficiency of medial circumflex femoral artery).
- Caused by trauma, high-dose corticosteroids, alcoholism, sickle cell.
7
Q
Lab values in bone disorders
- For each (increased/decreased)
- Serum Ca2+
- PO43-
- ALP
- PTH
- Comments
- Osteoporosis
- Osteopetrosis
- Paget disease
- Osteomalacia/rickets
A
- Osteoporosis
- Serum Ca2+: —
- PO43-: —
- ALP: —
- PTH: —
- Comments: Decreased bone mass
- Osteopetrosis
- Serum Ca2+: — / decreased
- PO43-: —
- ALP: —
- PTH: —
-
Comments: Dense, brittle bones.
- Ca2+ decreased in severe, malignant disease
- Paget disease
- Serum Ca2+: —
- PO43-: —
- ALP: Increased
- PTH: —
- Comments: Abnormal “mosaic” bone architecture
- Osteomalacia/rickets
- Serum Ca2+: Decreased
- PO43-: Decreased
- ALP: Increased
- PTH: Increased
- Comments: Soft bones
8
Q
Lab values in bone disorders
- For each (increased/decreased)
- Serum Ca2+
- PO43-
- ALP
- PTH
- Comments
- Hypervitaminosis D
- Osteitis fibrosa cystica
- 1° hyperparathyroidism
- 2° hyperparathyroidism
- General comments
A
- Hypervitaminosis D
- Serum Ca2+: Increased
- PO43-: Increased
- ALP: —
- PTH: Decreased
- Comments: Caused by over-supplementation or granulomatous disease (e.g., sarcoidosis)
- Osteitis fibrosa cystica
- 1° hyperparathyroidism
- Serum Ca2+: Increased
- PO43-: Decreased
- ALP: Increased
- PTH: Increased
- Comments: Idiopathic or parathyroid hyperplasia, adenoma, carcinoma
- 2° hyperparathyroidism
- Serum Ca2+: Decreased
- PO43-: Increased
- ALP: Increased
- PTH: Increased
- Comments: Often as compensation for ESRD (decreased PO43- excretion and production of activated vitamin D)
- General comments
- “Brown tumors” due to fibrous replacement of bone, subperiosteal thinning
- 1° hyperparathyroidism
9
Q
Giant cell tumor
- Type of tumor
- Epidemiology / location
- Characteristics
A
- Type of tumor
- Benign primary bone tumor
- Epidemiology / location
- 20–40 years old.
- Epiphyseal end of long bones.
- Characteristics
- Locally aggressive benign tumor often around knee.
- “Soap bubble” appearance on x-ray [A]
- Multinucleated giant cells.
10
Q
Osteochondroma (exostosis)
- Type of tumor
- Epidemiology / location
- Characteristics
A
- Type of tumor
- Benign primary bone tumor
- Epidemiology / location
- Most common benign tumor.
- Males < 25 years old.
- Characteristics
- Mature bone with cartilaginous cap.
- Rarely transforms to chondrosarcoma.
11
Q
Osteosarcoma (osteogenic sarcoma)
- Type of tumor
- Epidemiology / location
- Characteristics
A
- Type of tumor
- Malignant primary bone tumor
- Epidemiology / location
- 2nd most common 1° malignant bone tumor (after multiple myeloma).
- Bimodal distribution: 10–20 years old (1°), > 65 (2°).
- Predisposing factors: Paget disease of bone, bone infarcts, radiation, familial retinoblastoma, Li-Fraumeni syndrome (germline P53 mutation).
- Metaphysis of long bones, often around knee [B] [C].
- Characteristics
- Codman triangle (from elevation of periosteum) or sunburst pattern on x-ray.
- Aggressive.
- Treat with surgical en bloc resection (with limb salvage) and chemotherapy.
12
Q
Ewing sarcoma
- Type of tumor
- Epidemiology / location
- Characteristics
A
- Type of tumor
- Malignant primary bone tumor
- Epidemiology / location
- Boys < 15 years old.
- Commonly appears in diaphysis of long bones, pelvis, scapula, and ribs.
- Characteristics
- Anaplastic small blue cell malignant tumor [D].
- Extremely aggressive with early metastases, but responsive to chemotherapy.
- “Onion skin” appearance in bone.
- Associated with t(11;22) translocation.
- 11 + 22 = 33 (Patrick Ewing’s jersey number).
13
Q
Chondrosarcoma (423)
- Type of tumor
- Epidemiology / location
- Characteristics
A
- Type of tumor
- Malignant primary bone tumor
- Epidemiology / location
- Rare, malignant, cartilaginous tumor.
- Men 30–60 years old.
- Usually located in pelvis, spine, scapula, humerus, tibia, or femur.
- Characteristics
- Malignant cartilaginous tumor.
- May be of 1° origin or from osteochondroma.
- Expansile glistening mass within the medullary cavity.
14
Q
Osteoarthritis
- Etiology
- Joint findings
- Predisposing factors
- Classic presentation
- Treatment
A
- Etiology
- Mechanical—joint wear and tear destroys articular cartilage.
- Joint findings
- Subchondral cysts, sclerosis [A], osteophytes (bone spurs), eburnation (polished, ivory-like appearance of bone), Heberden nodes (DIP), and Bouchard nodes (PIP).
- No MCP involvement.
- Predisposing factors
- Age, obesity, joint deformity, trauma.
- Classic presentation
- Pain in weight-bearing joints after use (e.g., at the end of the day), improving with rest.
- Knee cartilage loss begins medially (“bowlegged”).
- Noninflammatory.
- No systemic symptoms.
- Treatment
- NSAIDs, intra-articular glucocorticoids.
15
Q
Rheumatoid arthritis
- Etiology
- Joint findings
- Predisposing factors
- Classic presentation
- Treatment
A
- Etiology
- Autoimmune—inflammatory destruction of synovial joints.
- Mediated by cytokines and type III and type IV hypersensitivity reactions.
- Joint findings
- Pannus formation in joints (MCP, PIP), subcutaneous rheumatoid nodules (fibrinoid necrosis), ulnar deviation of fingers, subluxation [B], Baker cyst (in popliteal fossa).
- No DIP involvement.
- Predisposing factors
- Females > males.
- 80% have (+) rheumatoid factor (anti-IgG antibody)
- Anti–cyclic citrullinated peptide antibody is more specific.
- Strong association with HLA-DR4.
- Classic presentation
- Morning stiffness lasting > 30 minutes and improving with use, symmetric joint involvement, systemic symptoms (fever, fatigue, pleuritis, pericarditis).
- Treatment
- NSAIDs, glucocorticoids, disease-modifying agents (methotrexate, sulfasalazine, TNF-α inhibitors).