Page 613 - Concise Pathology for Exam Preparation ( PDFDrive )

598 SECTION II Diseases of Organ Systems

Q. Write briefly on gouty arthritis.

Ans. Salient features of gouty arthritis:
• Gouty arthritis is a male dominant disease, characterized by hyperuricaemia with
plasma urate level more than 7 mg/dL (upper limit of solubility of MSU in serum at
37°C and blood pH).
• It involves the metatarsophalangeal joints followed by ankles and knees; wrists may be
affected later.
• Typical manifestations include recurrent attacks of acute arthritis and deposits of MSU
tophi (meaning porous stones) in soft tissue and renal disease affecting interstitium and
blood vessels (uric acid nephrolithiasis).

Types
• Metabolic gout (10% cases): Due to disorder in metabolism of uric acid (a product of
purine metabolism) leading to its overproduction.
• Renal gout (90% cases): Due to reduced renal excretion of uric acid secondary to dia-
betes mellitus, leukaemia, diuretic therapy, treatment of disseminated cancer and drugs
like aspirin, pyrazinamide, nicotinic acid, ethambutol and ethanol.

Pathogenesis (Flowchart 21.6)

Interaction of MSU crystals with mononuclear phagocytes and neutrophils

Stimulates the production of IL-1 MSU crystals lyse neutrophils

Neutrophils release lysosomal
enzymes and free radicals

Inflammatory reaction
FLOWCHART 21.6. Pathogenesis of gouty arthritis

X-Ray
Juxta-articular bone erosion by crystal deposits with loss of joint space.

Pathology

• Acute gout: Predominantly a disease of lower extremities, acute gout most commonly
affects the great toe. It is triggered by precipitation of needle-shaped crystals of MSU
from serum or synovial fluid, which leads to an intensely painful joint effusion contain-
ing crystals, polymorphs and macrophages, lasting for hours to week.
• Chronic gout: This is characterized by presence of tophi, which usually develop after
approximately 10 years of disease. Tophi represent deposits of MSU that occur in tissue
most commonly in and around the affected joints. Sections through a tophus exhibit an
exuberant granulomatous reaction complete with foreign body multinucleated giant
cells surrounding a central core of amorphous MSU crystals.
• Pseudogout: Characterized by deposition of calcium pyrophosphate dihydrate crystals
in the joint cavities, pseudogout can be sporadic (idiopathic), hereditary or secondary.
The knee joint is affected in more than 50% cases and the age of the patients is more
than 50 years. The crystals are rhomboid in shape and deposit in the articular cartilage
(chondrocalcinosis). It may be asymptomatic or manifest as acute, subacute or chronic
arthritis.

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