Gout

Definition

A joint disease caused by high levels of uric acid in the blood.

Epidemiology

Pathophysiology

It is a disease of purine metabolism resulting in high uric acid levels. Uric acid is the final metabolite of this process.

When it is deposited in joints in high levels it forms crystals causing a localised inflammatory response.

Risk Factors

There are a variety of risk factors@

• Lifestyle - foods such as meat, alcohol, sweetened drinks (with fructose) and seafood. Coffee, vitamin C and physical fitness decrease risk.
• Genetics - there appears to be some genetic variability in uric acid production. There are a whole bunch of hereditary disorders too (you don't need to know them - they're really rare.)
• Medical - metabolic syndrome involves gout in 75% of cases. Renal failure, polycythaemia, haemolytic anaemia, psoriasis can all cause it. (Lead poisoning and organ transplants can too.)

Clinical Features

The exam question will say:

SWOLLEN BIG TOE - you will think GOUT! It is involved in 50% of cases. However, any joint can be affected.

• 2-4 hour onset
• begins at night (as body temperature is lower)
• tophi - deposits of monosodium urate usually found on the elbow (another med school classic)
• fatigue
• high fever

Investigations

Bloods

• Uric acid
• FBC - rule out polycythaemia
• U+Es - rule out renal failure (NB: renal failure can cause gout due to impaired uric acid excretion but can also result from gout due to crystal deposition in the kidney.)

Imaging

• X-ray of affected joint to rule out other pathology

Management

Acute

1. NSAIDSs - whack them on some ibuprofen
2. Colchicine - if they can't have NSAIDs (upper GI bleed, gastritis etc.). Side-effects - GI upset
3. Steroids - if all else fails

Prophylactic

Allopurinol is the treatment of choice. Don't use it in acute attacks but it will stave off further ones.