Page 610 - Concise Pathology for Exam Preparation ( PDFDrive )

21 Musculoskeletal System 595

Genetic and biochemical factors Chondrocyte injury

IL-1, TNF

Catabolic metalloproteinases (collagenase and stromelysin)

Destroy articular cartilage matrix
(fibrillation and erosion of cartilage surface)
Release of proteoglycan and collagen
fragments into the synovial fluid
Exposed subchondral bone becomes new articular surface

Bone surface resembles ivory
FLOWCHART 21.4. Pathogenesis of osteoarthritis

Pathogenesis (Flowchart 21.4)
Genetic and biochemical factors lead to chondrocytes injury. In early OA, chondrocytes
proliferate and release inflammatory mediators which result in injury to the synovium and
subchondral bone. In late OA, repeated/persistent inflammation leads to chondrocytes
drop out, loss of cartilage and subchondral bone alterations.

Diagnosis
There is no specific laboratory test for osteoarthritis, no means of preventing primary
osteoarthritis and no definite methods for arresting its progression.

Q. Outline the aetiopathogenesis and clinicopathological features
of rheumatoid arthritis (RA).
Ans. RA is a chronic, nonsuppurative, autoimmune disease.

Clinical Features

• It is a multisystem disease which involves three or more joints and has an insidious
onset.
• Occurs between 40 and 70 years of age and shows female preponderance.
• Commonly affected joints include metacarpophalangeal and proximal interphalangeal
joints of hands along with larger joints like wrists, elbows, ankles and knees.
• Morning stiffness lasting longer than 1 h before improvement is a classic feature (unlike
osteoarthritis in which the pain and stiffness gets worse with progressive use of the joint
during the day).
• Advanced disease in the hands and wrists produces ulnar deviation of the fingers (Swan
neck deformity) and may lead to laxity of the soft tissues.
• Carpal tunnel syndrome (compression of median nerve) is a common manifestation.
• Also seen are general malaise, weakness, fever of unknown origin, weight loss, myalgias
and inflammation of tendons and bursae.

Extra-Articular Manifestations of RA

• Subcutaneous (rheumatoid) nodules, which occur on extensor surface of limbs, occiput
and sacrum
• Cardiac involvement (carditis) and medium-to-small vessel vasculitis
• Skin ulceration, gangrene and obliterative endarteritis (associated with high titres of RA)

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