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Gout and Pseudogout

Gout is formed of Uric acid crystals. Pseudogout is formed of Calcium pyrophosphate crystals. Both present with a hot, swollen, stiff, painful joint, but a key differential of septic arthritis needs to be ruled out first!

Investigations

Joint aspiration is needed for a definitive diagnosis. A polarised light microscopy is done subsequently to differentiate between the 2 types:

  • Uric acid crystals - Needle-shaped, Negative birefringent (NN)

  • Calcium pyrophosphate crystals - Rhomboid-shaped, Positive birefringent

  • To differentiate it from septic arthritis, MC&S will show:

    • No bacteria (presence of bacteria → septic arthritis)

    • Raised WCC (a much higher value → septic arthritis)


XR may show Chondrocalcinosis as a thin white line in the joint space.


Bloods:

  • Uric acid – Lowering the levels of this (e.g. w/allopurinol), will reduce the risk of further attacks

  • U&E – Renal impairment is a risk factor for gout


N.B. Thiazide and loop diurectics, Low-dose aspirin, and Chemotherapy can cause hyperuricaemia, therefore increasing the risk of gout.


Management

Acute attack:

  • Supportive as symptoms usually resolve over several weeks

  • NSAIDs

  • Colchicine is an alternative if NSAIDs contraindicated e.g. CKD, but it carries a high risk of GI disturbance, esp. diarrhoea

  • Steroids if stage 5 CKD


Prophylactic - Allopurinol (1st line)


N.B. Co-prescribe a PPI for those at high risk of GI complications.




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