Musculoskeletal Pathology:Most know area

Musculoskeletal Pathology:Most know area




Hereditary Disorders



Osteogenesis imperfecta

· Many types

· Mutations of collagen type 1

· Multiple fractures

· Dentinogenesis imperfecta



Achondroplasia

· 20% autosomal dominant; 80% random mutations

· Most common form of inherited dwarfism

· Epiphyseal plates close prematurely

· Cor pulmonale



Osteopetrosis

· Autosomal dominant or recessive

· Osteoclast hypofunction causes very dense bone

· AR: severe, with anemia, nerve entrapment, hydrocephalus, infections, fractures

· AD: milder



Non-Neoplastic Disorders



Fracture

· Inflammatory phase (first week; clot and callus formation)

· Reparative phase (months; callus bridge)

· Remodeling phase (weeks-years; remodeling of callus)



Osteonecrosis

· Ischemic death of bone without infection

· Physical event: trauma, embolism, radiation

· Systemic disease: sickle cell, lupus, gout

· Toxic effect: corticosteroids, alcoholism



Myositis Ossificans

· Reactive bone formation within muscle

· Caused by trauma

· Looks like a neoplasm

· Lower limbs



Osteomyelitis

· Bone inflammation caused by infection

· Staph, Strep, E. coli, N. gonorrhea, H. influenzae, Salmonella

· Results from direct penetration or hematogenous spread

· Sequestrum (necrotic bone fragment) eventually covered by involucrum (new periosteal bone)



Osteoporosis

· Decreased bone mass per unit volume

· Normal ratio of mineral to matrix

· Primary occurs in elderly women (decreased estrogen, less exercise)

· Secondary occurs with corticosteroid use, alcoholism



Paget Disease

· Disorder of bone remodeling

· Three phases (hot, mixed, cold)

· Bones of skull: cotton wool appearance, hypercementosis of jaws

· Tests: alkaline phosphatase, urine hydroxyproline



Fibrous Dysplasia

· Monostotic

· Ground glass appearance on xray

· McCune Albright syndrome

· Jaffe syndrome



Osteoarthritis

· Most common joint disease

· Primary (cartilage defect), secondary (to trauma, crystal deposits, infection)

· Weight-bearing joints (knees, hips, spine) and hands

· Eburnated (very dense, ivory-like) bone, Haberden nodes



Rheumatoid Arthritis

· Chronic, systemic, autoimmune, inflammatory disease

· Symmetrical small-joint involvement

· Starts as synovial disease (hyperplastic synovium, pannus)

· Rice bodies, rheumatoid nodules



Gout

· Increased serum urate leads to urate crystals in joints, kidneys

· Primary or secondary (malignancy, alcoholism)

· Acute gout (podagra), tophaceous gout (tophi in ear, Achilles tendon)

· Histology: Granulomas with needle-shaped crystals





Muscle Disorders



Duchenne Muscular Dystrophy

· X-linked

· Deletion of dystrophin gene

· Degeneration of muscles

· Wheelchair-bound by age 10-15; death from respiratory insufficiency or arrhythmia



Myotonic Dystrophy

· Autosomal dominant

· Atrophy of type I fibers, hypertrophy of type II fibers

· Muscle weakness and sustained muscular contractions

· Gets worse from one generation to next