Gout

Question 1

Define

Answer 1

A disorder of uric acid metabolism causing recurrent bouts of acute arthritis caused by deposition of monosodium urate crystals in joints, and also soft tissues and kidneys

↘ Sodium urate crystals are negatively birefringent under polarised light

Soft tissues: urate deposits form tophi
Kidneys: cause renal disease (stones, interstitial nephritis)

Question 2

Causes

Answer 2

• Aetiology → deposition of monosodium urate crystals in and near joints
• Precipitated by → trauma, surgery, starvation, infection, diuretics

Associated with raised plasma urate

Cause → Hereditary, cytotoxics (tumour lysis)

1. ↑intake/production – ↑dietary purines, ↑purine turnover (e.g. leukaemia, lymphoma)
2. ↓renal excretion: idiopathic, drugs (e.g. alcohol excess, diuretics), renal dysfunction

Question 3

Risk factors

Answer 3

FHx, obesity, alcohol, ↑red meat, drugs

Drugs causing ↓renal excretion ‘CANT LEAP’:

• Cyclosporin,
• Alcohol,
• Nicotinic acid,
• Thiazides,
• Loop Diuretics
• Ethambutol
• Aspirin
• Pyrazinamide

Question 4

Epidemiology

Answer 4

10 x more common in MALES

Very rare pre-puberty

Rare in pre-menopausal women

More common in HIGHER social classes

Question 5

Symptoms

Answer 5

Typically presents with an acute monoarthropathy with severe joint inflammation

Acute attack – precipitated by the above

• Sudden excruciating monoarticular pain: >50% occur at

the metatarsophalangeal joint of the big toe (podagra)

Also ankle, foot, small joints of hand, wrist, elbow or knee

• Severe joint inflammation
• ±Cellulitis, polyarticular/periarticular involvement

Symptoms peak at 24hrs, resolve in 7-10 days
Attacks often recurrent with symptom free period in between

• Intercritical gout – asymptomatic period between acute attacks
• Chronic tophaceous gout – follows repeated acute attacks, persistent low-grade fever, polyarticular pain with painful tophi (urate deposits), best seen on tendons and the pinna of the ear

Question 6

Investigations

Answer 6

Synovial Fluid Aspirate

• Monosodium urate crystals will be seen

They are:

• Needle-shaped
• NEGATIVE birefringence under polarised light microscopy

Microscopy and culture will also be performed to exclude septic arthritis

Bloods

• FBC - raised WCC
• U&Es
• Raised urate
• Raised ESR

AXR/KUB Film

• Uric acid renal stones may be seen