Summary

Pseudogout is an acute crystal arthropathy caused by deposition of calcium pyrophosphate dihydrate (CPPD) crystals in articular cartilage and subsequent release into joint fluid. Unlike gout (monosodium urate crystals), pseudogout primarily affects older patients and classically involves the knee or wrist. The condition is clinically indistinguishable from septic arthritis and gout, making joint aspiration essential for diagnosis. Radiographic chondrocalcinosis (cartilage calcification) is highly supportive but not diagnostic.

Key Facts

• Definition: Acute inflammatory arthritis caused by CPPD crystal deposition
• Prevalence: Increases with age; 15-30% of elderly have radiographic chondrocalcinosis
• Key Joints: Knee (50%), wrist (30%), shoulders, ankles, elbows
• Crystal Features: Weakly positively birefringent rhomboid crystals (vs gout: negative needle)
• Radiographic Sign: Chondrocalcinosis — linear calcification in fibrocartilage and hyaline cartilage
• "3 H's": Associated with Hyperparathyroidism, Haemochromatosis, Hypomagnesaemia

Clinical Pearls

Blue = Positive = Pseudogout: Under polarised microscopy, CPPD crystals are rhomboid and weakly POSITIVELY birefringent (blue when parallel to compensator). Gout = negative needle (yellow when parallel).

Always Aspirate: Acute monoarthritis in an elderly patient is septic arthritis until proven otherwise. You CANNOT distinguish pseudogout from septic arthritis clinically — aspiration is mandatory.

Young Pseudogout = Metabolic Screen: CPPD disease in patients <55 years should prompt investigation for underlying metabolic causes: calcium, magnesium, ferritin, and parathyroid hormone.

Why This Matters Clinically

Pseudogout is a common cause of acute joint pain in elderly patients and is frequently encountered in hospital medicine. The critical clinical issue is distinguishing it from septic arthritis, which requires joint aspiration. Missing septic arthritis can lead to joint destruction, sepsis, and death.

Structured Approach

General:

• Assess for systemic illness (fever, tachycardia)
• Look for features of metabolic causes (skin bronzing = haemochromatosis)
• Check other joints (polyarticular involvement)

Joint Examination:

• Inspect for swelling, erythema
• Palpate for warmth, effusion, tenderness
• Assess active and passive range of motion
• Check for instability or crepitus

Special Tests

Natural History

Acute attacks are self-limiting, typically resolving over 1-3 weeks even without treatment. Recurrence is common. Chronic CPPD deposition contributes to joint degeneration over time. Unlike gout, there is no curative treatment — management is symptomatic.

Outcomes with Treatment

Prognostic Factors

Good Prognosis:

• Single joint involvement
• Responsive to treatment
• No underlying metabolic cause
• Infrequent attacks

Poor Prognosis:

• Recurrent attacks
• Polyarticular disease
• Underlying metabolic disorder (if untreated)
• Severe joint damage at presentation

Key Guidelines

1. EULAR (2011) — Recommendations for diagnosis and management of CPPD. Emphasise aspiration for diagnosis; intra-articular steroid as first-line for acute attacks.

2. ACR/EULAR (2015 Updates) — Support colchicine for prophylaxis in recurrent disease; recommend metabolic screening in young patients.

Landmark Studies

McCarty & Hollander (1961) — Original description of CPPD crystals

• First identified CPPD as distinct from urate crystals
• Clinical Impact: Established pseudogout as separate entity from gout

Zhang et al. (2011) — EULAR systematic review

• Comprehensive review of CPPD diagnosis and management
• Key finding: Intra-articular corticosteroids effective; no disease-modifying therapy
• Clinical Impact: Established evidence-based management recommendations

Rosenthal & Ryan (2016) — Pathogenesis review

• Elucidated role of NLRP3 inflammasome in CPPD inflammation
• Clinical Impact: Explains why IL-1 inhibitors may work in refractory cases

Evidence Strength

What is Pseudogout?

Pseudogout is a condition where crystals build up in your joint cartilage and then suddenly cause intense pain and swelling. These crystals are made of calcium pyrophosphate (different from the uric acid crystals in regular gout). It's called "pseudo" (meaning false) gout because it causes very similar symptoms to gout but needs different treatment.

Why does it matter?

Pseudogout attacks can be extremely painful and make it hard to walk or use the affected joint. The main concern is that it looks exactly like a joint infection (septic arthritis), which is very serious. That's why doctors usually need to take a small sample of fluid from your joint to check for crystals and infection.

How is it treated?

1. Draining the joint: Taking fluid out provides immediate relief and allows testing to confirm the diagnosis.

2. Steroid injection: An injection into the joint is often the best treatment for a single swollen joint.

3. Anti-inflammatory tablets: NSAIDs (like ibuprofen or naproxen) or colchicine can reduce inflammation.

4. Steroids tablets: If the injection isn't suitable, steroid tablets work well.

5. No cure: Unlike gout, there's no treatment that removes the crystals permanently. Treatment focuses on managing attacks when they happen.

What to expect

• Attacks usually settle within 1-2 weeks with treatment
• You may have future attacks — this is normal
• If attacks are frequent, a daily low-dose medication can reduce them

When to seek help

See a doctor urgently if:

• You have sudden severe joint pain with swelling
• You have a fever with joint pain
• You recently had a joint injection or surgery
• The joint becomes red and hot