Gout and Pseudogout: A PLAB 1 Focus
Gout and pseudogout are common inflammatory arthropathies that present with acute, painful joint effusions. Understanding their distinct etiologies, clinical presentations, diagnostic approaches, and management strategies is crucial for PLAB 1 success. This module will equip you with the advanced clinical knowledge and UK guideline insights needed to confidently manage these conditions.
Understanding Gout
Gout is a metabolic disorder characterized by the deposition of monosodium urate (MSU) crystals in joints and tissues, leading to recurrent episodes of acute inflammatory arthritis. It is caused by hyperuricemia, a condition where there is an excess of uric acid in the blood.
Clinical Presentation of Gout
Gout typically presents as a sudden, severe onset of pain, swelling, redness, and warmth in a single joint. The most common initial presentation is podagra, affecting the big toe.
| Feature | Gout |
|---|---|
| Onset | Sudden, often nocturnal |
| Affected Joints | Most commonly 1st MTP joint (podagra), ankles, knees, wrists, elbows |
| Pain Severity | Excruciating, often described as unbearable |
| Associated Symptoms | Fever, chills, malaise during acute attacks |
| Tophi | Urate crystal deposits in chronic gout, can be visible or palpable |
Diagnosis of Gout
The gold standard for diagnosing gout is the identification of MSU crystals in synovial fluid obtained from an affected joint.
Management of Gout
Management involves treating acute attacks and preventing future flares and complications.
| Phase | Treatment Options (UK Guidelines) |
|---|---|
| Acute Attack | NSAIDs (e.g., naproxen, indometacin) - first-line if no contraindications. Colchicine - effective if started within 12-24 hours of symptom onset. Corticosteroids (oral or intra-articular) - for patients intolerant to NSAIDs/colchicine or with contraindications. |
| Prophylaxis (Preventing Flares) | Allopurinol or Febuxostat (uricosuric agents if contraindications to xanthine oxidase inhibitors) - initiated after acute attack subsides, aiming for serum uric acid < 360 µmol/L (or <300 µmol/L if tophi present). Low-dose colchicine or NSAIDs may be used concurrently during initiation of urate-lowering therapy to prevent flares. |
| Chronic Management | Lifestyle modifications: weight loss, reduced alcohol intake, avoidance of purine-rich foods. Regular monitoring of serum uric acid levels. |
Remember: Urate-lowering therapy should NOT be initiated during an acute gout attack. It should be started once the inflammation has resolved to avoid prolonging the attack.
Understanding Pseudogout (Calcium Pyrophosphate Deposition Disease - CPPD)
Pseudogout, also known as calcium pyrophosphate deposition disease (CPPD), is another crystal-induced arthropathy. However, it is caused by the deposition of calcium pyrophosphate dihydrate (CPPD) crystals in joints and cartilage.
Clinical Presentation of Pseudogout
Pseudogout attacks can mimic gout, but often affect different joints and may have a less explosive onset.
| Feature | Pseudogout (CPPD) |
|---|---|
| Onset | Can be sudden or gradual |
| Affected Joints | Most commonly knees, wrists, shoulders, hips; can affect multiple joints |
| Pain Severity | Moderate to severe |
| Associated Symptoms | Swelling, redness, warmth; less commonly fever/malaise than gout |
| Radiographic Findings | Chondrocalcinosis (calcification of cartilage) is a hallmark on X-ray |
Diagnosis of Pseudogout
Similar to gout, the definitive diagnosis of pseudogout is made by identifying CPPD crystals in synovial fluid.
Management of Pseudogout
Management focuses on relieving acute inflammation and addressing any underlying causes.
| Phase | Treatment Options (UK Guidelines) |
|---|---|
| Acute Attack | NSAIDs (first-line if no contraindications). Colchicine (less effective than in gout). Corticosteroids (oral or intra-articular) - often very effective, especially for knee effusions. |
| Chronic Management | Management of underlying conditions (e.g., iron chelation for hemochromatosis, parathyroidectomy for hyperparathyroidism). No specific urate-lowering therapy equivalent for CPPD. Symptomatic relief and management of chronic arthritis. |
Key Differences and Similarities for PLAB 1
While both conditions cause inflammatory arthritis due to crystal deposition, their causative crystals, typical joint involvement, and long-term management differ significantly.
Visualizing the crystals under polarized light microscopy is key to differentiating gout and pseudogout. Gout crystals are needle-shaped and negatively birefringent, appearing yellow when parallel to the axis of the polarizer. Pseudogout crystals are rhomboid-shaped and positively birefringent, appearing blue when parallel to the axis of the polarizer. This distinction is critical for accurate diagnosis and management.
Text-based content
Library pages focus on text content
Synovial fluid analysis to identify the specific crystals (MSU for gout, CPPD for pseudogout).
The first metatarsophalangeal (MTP) joint (podagra).
Chondrocalcinosis (calcification of articular cartilage).
UK Guidelines Summary Points
NICE guidelines (and similar UK recommendations) emphasize prompt treatment of acute attacks, appropriate use of urate-lowering therapy for gout, and investigation for secondary causes of CPPD.
For gout, the target serum urate level for long-term management is typically <360 µmol/L (or <300 µmol/L if tophi are present).
Always consider and investigate for underlying conditions that may predispose to CPPD, such as hemochromatosis, hyperparathyroidism, and hypomagnesemia.
Learning Resources
Provides comprehensive guidance on the diagnosis and management of gout, including treatment options and lifestyle advice, aligned with UK clinical practice.
An in-depth overview of CPPD, covering its epidemiology, pathogenesis, and genetics, offering detailed clinical insights for advanced understanding.
A patient-friendly overview of gout from the NHS, explaining symptoms, causes, and treatment, useful for understanding the patient perspective and common advice.
Provides accessible information on pseudogout, its symptoms, causes, and management, complementing the clinical knowledge with patient-centric details.
A clear and concise video explaining the pathophysiology, clinical presentation, and management of gout, ideal for visual learners.
A blog post discussing crystal-induced arthropathies, offering a good overview and comparison of gout and pseudogout from a medical education perspective.
The official classification criteria for gout, essential for understanding the diagnostic framework used in clinical research and practice.
A detailed guide from the Arthritis Foundation covering causes, symptoms, diagnosis, and treatment of gout, offering a well-rounded perspective.
A comprehensive medical overview of CPPD, including detailed information on diagnosis, differential diagnosis, and treatment strategies.
The official NICE guideline for the management of gout in adults, providing the most current and authoritative recommendations for UK clinical practice.