Gout and Pseudogout

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | References

Definition

Gout: Gout is a type of inflammatory arthritis characterised by sudden, severe episodes of pain, redness, and swelling in the joints, most commonly the big toe. It is caused by the deposition of monosodium urate crystals in the joint.

Pseudogout: Pseudogout, also known as calcium pyrophosphate deposition (CPPD) disease, is a form of arthritis similar to gout but caused by the deposition of calcium pyrophosphate crystals in the joints, leading to pain, swelling, and stiffness.

Aetiology

Gout:

• Hyperuricaemia, where elevated levels of uric acid in the blood lead to the formation of urate crystals.
• Factors contributing to hyperuricaemia include genetics, diet (high in purines, such as red meat and seafood), alcohol consumption, obesity, and certain medications (e.g., diuretics).
• Renal impairment, leading to decreased uric acid excretion.

Pseudogout:

• Deposition of calcium pyrophosphate dihydrate (CPPD) crystals in the joint cartilage, which may be associated with aging.
• Secondary causes include joint trauma, genetic predisposition, metabolic disorders (e.g., hyperparathyroidism, haemochromatosis), and electrolyte imbalances.

Pathophysiology

Gout:

• Hyperuricaemia leads to the supersaturation of uric acid in the blood, resulting in the formation of monosodium urate crystals.
• These crystals deposit in the synovial fluid of joints, initiating an intense inflammatory response by activating the immune system.
• The inflammation results in the characteristic pain, redness, and swelling seen in acute gout attacks.

Pseudogout:

• Calcium pyrophosphate crystals form in the cartilage, leading to chondrocalcinosis (visible on X-rays).
• These crystals shed into the joint space, triggering an inflammatory response similar to that seen in gout.
• The resulting inflammation causes joint pain, swelling, and stiffness, typically in larger joints such as the knee.

Risk Factors

Gout:

• Male gender, especially middle-aged men
• Family history of gout
• Diet high in purines (e.g., red meat, seafood), alcohol consumption, particularly beer, and sugary drinks
• Obesity
• Renal impairment or chronic kidney disease
• Use of certain medications, such as diuretics and low-dose aspirin

Pseudogout:

• Older age, as the risk increases with age
• Joint trauma or surgery
• Family history of pseudogout or chondrocalcinosis
• Metabolic disorders such as hyperparathyroidism, haemochromatosis, or hypothyroidism
• Electrolyte imbalances, particularly low magnesium or high calcium levels

Signs and Symptoms

Gout:

• Sudden onset of severe pain, redness, and swelling in a joint, most commonly the big toe (podagra)
• Warmth and tenderness in the affected joint
• Possible fever during acute attacks
• Tophi, which are deposits of urate crystals, may develop in chronic cases, particularly in the ears, elbows, or Achilles tendons

Pseudogout:

• Acute pain, swelling, and stiffness in larger joints, commonly the knee or wrist
• Similar symptoms to gout but typically affects different joints
• Chronic joint pain and damage may develop over time if left untreated

Investigations

Gout:

• Serum uric acid levels: May be elevated during an attack, but normal levels do not exclude gout.
• Joint aspiration: Analysis of synovial fluid under polarised light microscopy to identify monosodium urate crystals, which appear needle-shaped and negatively birefringent.
• X-rays: Generally not required for diagnosis but may show advanced joint damage or tophi in chronic gout.

Pseudogout:

• Joint aspiration: Synovial fluid analysis to identify calcium pyrophosphate crystals, which are rhomboid-shaped and positively birefringent under polarised light microscopy.
• X-rays: To detect chondrocalcinosis (calcification of cartilage) and to assess joint damage.
• Blood tests: To rule out other conditions and check for associated metabolic disorders, such as hypercalcaemia or hypomagnesaemia.

Management

Primary Care Management

Gout:

• Acute attack management: NSAIDs (e.g., ibuprofen) or colchicine for pain relief. Corticosteroids may be considered if NSAIDs are contraindicated.
• Long-term management: Allopurinol or febuxostat to lower serum uric acid levels. Lifestyle modifications, including dietary changes, weight loss, and reduced alcohol intake.

Pseudogout:

• Acute attack management: NSAIDs or colchicine to manage pain and inflammation. Corticosteroids may be used if NSAIDs are contraindicated.
• Chronic management: Address underlying metabolic disorders and consider regular use of colchicine for recurrent attacks.

Specialist Management

Gout:

• Referral to rheumatology: For complex or refractory cases requiring specialist input.
• Management of tophi: Surgical removal may be considered in severe cases, though medical management is preferred.

Pseudogout:

• Joint aspiration and injection: Repeated joint aspirations and corticosteroid injections may be necessary for recurrent episodes, especially in patients with significant symptoms that do not respond to initial treatments.
• Management of underlying conditions: Addressing associated metabolic disorders such as hyperparathyroidism, haemochromatosis, or hypothyroidism, which can help prevent further pseudogout attacks.
• Physical therapy: In some cases, physiotherapy may be recommended to help maintain joint function and mobility, especially in patients with chronic pseudogout.

References

1. NHS (2024) Gout. Available at: https://www.nhs.uk/conditions/gout/ (Accessed: 24 June 2024).
2. National Institute for Health and Care Excellence (2024) Gout and Pseudogout. Available at: https://cks.nice.org.uk/topics/gout/ (Accessed: 24 June 2024).
3. British Medical Journal (2024) Gout and Pseudogout: Clinical Features, Diagnosis, and Management. Available at: https://www.bmj.com/content/350/bmj.h2963 (Accessed: 24 June 2024).
4. American College of Rheumatology (2024) Gout and Pseudogout. Available at: https://www.rheumatology.org/I-Am-A/Patient-Caregiver/Diseases-Conditions/Gout (Accessed: 24 June 2024).

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