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M08.027.004 Arthritis related to crystal deposition
Gout and pseudogout are two distinct crystal deposition diseases that can cause acute arthritis and present with similar symptoms. However, their underlying causes, clinical presentations, and treatment approaches differ. This guide provides a comprehensive overview of both conditions, aiding medical students in accurate diagnosis and management.
Gout
Description:
Gout is a chronic inflammatory arthritis caused by the deposition of monosodium urate (MSU) crystals in joints and periarticular tissues. It is characterized by recurrent episodes of acute arthritis, often involving the first metatarsophalangeal joint (big toe). Hyperuricemia, or elevated serum uric acid levels, is a prerequisite for gout development.
Types of Gout:
- Primary Gout (90%): Idiopathic in origin, affecting males more commonly and typically presenting in older adults.
- Secondary Gout (10%): Triggered by underlying medical conditions or medications that increase uric acid production or decrease its excretion.
Clinical Features:
- Acute Gout Attacks: Characterized by sudden onset of severe pain, swelling, redness, and warmth in the affected joint, most commonly the first metatarsophalangeal joint (podagra). Other joints like the ankle, knee, wrist, and elbow can also be involved.
- Tophi: Deposits of MSU crystals surrounded by inflammatory tissue, which can form over joints, bursae, and tendons.
- Joint Destruction and Deformity: Chronic gout can lead to progressive joint damage and deformity in affected joints.
- Uric Acid Nephropathy: Elevated uric acid levels can contribute to kidney stones and renal insufficiency.
Diagnosis:
- Clinical Presentation: The characteristic sudden onset of severe joint pain, particularly in the great toe, is suggestive of gout.
- Joint Aspiration and Crystal Analysis: Microscopic examination of joint fluid aspirate to identify needle-shaped, negatively birefringent MSU crystals is the gold standard for diagnosis.
- Serum Uric Acid Levels: While elevated uric acid levels are often present, they can also be normal during acute attacks.
Treatment:
- Acute Gout Attacks: Focuses on rapid pain relief and inflammation control using nonsteroidal anti-inflammatory drugs (NSAIDs), colchicine, or corticosteroids.
- Uric Acid Lowering Therapy: Aims to prevent future gout attacks by lowering serum uric acid levels with medications like allopurinol (xanthine oxidase inhibitor) or probenecid (increases uric acid excretion).
Table 1. Summary of Gout Characteristics
| Feature | Description |
|---|---|
| Type | Primary (idiopathic) or Secondary (due to other conditions) |
| Clinical Features | Sudden joint pain, swelling, redness, warmth (often big toe) |
| Diagnosis | Joint aspiration with MSU crystal identification |
| Treatment | NSAIDs, colchicine, allopurinol, probenecid |
Points to Remember:
- Early diagnosis and treatment of gout are crucial to prevent joint damage and complications.
- Lifestyle modifications, including weight management and dietary adjustments, can help manage gout.
Pseudogout
Description:
Pseudogout, also known as chondrocalcinosis, is an inflammatory arthritis caused by the deposition of calcium pyrophosphate dihydrate (CPPD) crystals in joints and periarticular tissues. It can mimic gout but has distinct characteristics.
Clinical Features:
- Acute Pseudogout Attacks: Similar to gout, with sudden onset of joint pain, swelling, redness, and warmth. The knee joint is most commonly affected, unlike gout’s predilection for the big toe.
- Chronic Pseudogout: May present with a more gradual onset of joint pain and stiffness, mimicking osteoarthritis.
- Association with Underlying Conditions: Pseudogout is often associated with metabolic disorders like diabetes mellitus, hypothyroidism, and ochronosis.
Diagnosis:
- Clinical Presentation: While presentation can overlap with gout, knee joint involvement is more suggestive of pseudogout.
- Joint Aspiration and Crystal Analysis: Microscopic examination of joint fluid aspirate to identify rhomboid-shaped, weakly birefringent CPPD crystals is essential for diagnosis.
- Serum Uric Acid Levels: Unlike gout, serum uric acid levels are usually normal in pseudogout.
Treatment:
- Acute Pseudogout Attacks: Similar to gout, focuses on rapid pain relief and inflammation control using NSAIDs or corticosteroids.
- Long-Term Management: This may involve treating underlying medical conditions and using prophylactic medications like low-dose colchicine to prevent future attacks.