Rheumatology - Gout

Question 1

What is gout?

Answer 1

-Inflammatory arthritis associated with hyperuricaemia and intra-articular Na+ urate crystals

Question 2

What is the pathogenesis of gout

Answer 2

• Many patients there is no obvious cause
• Impaired excretion of uric acid: CKD, drugs (thiazidess, low dose aspirin, HTN, hypothyroidism, G6PD deficiency, increased lactic acid production)
• Increased production of uric acid: very weird diseases due to de novo mutations
• Acute gout precipitation: ingestion of polymorpholeucocytes of Na-Urate crystals causing the release of pro-inflammatory cytokines from phagosomes and complement activation.

Question 3

What are clinical features of gout?

Answer 3

• Typically middle-aged male with sudden onset of agonising pain, swelling and redness of the first MTP joint
• Attacks can occur any time but may be precipitated by too much food/alcohol/dehydration/new diuretic rx
• Attacks last approx 7 days, in 25% there is another joint affected as well.
• Severe attacks: difficult to distinguish clinically from infective cellulitis

Question 4

Ix for gout

Answer 4

• Clinical picture often diagnostic + rapid response to NSAIDs or colchicine
• Joint fluid microscopy: most specific test - will show needle-shaped monosodium urate crystals displaying negative birefringence under polarised light
• Serum uric acid: usually raised (>600 micro-mol/L) - if not recheck after few weeks b/c level falls immediately after acute attack.
• Serum urea and creatinine: monitored for signs of renal impairment

Question 5

Rx: basic rx (not allopurinol) for gout

Answer 5

• NSAIDs/coxibs at high doses rapidly reduce pain/swelling
• analgesia: Naproxen and diclofenac
• Dietary advice: advice pts to reduce alcohol intake (esp beer), total calorie and cholesterol intake and avoid purine rich food (shellfish/spinach)

Question 6

What is allopurinol MOA?

Answer 6

◦ Allopurinol MOA: blocks enzyme xanthine oxidase, which converts xanthine into uric acid.

Question 7

What are the S/E of allopurinol

Answer 7

Most common: skin rashes and grastro-intestinal intolerance

Most serious: bone marrow suppression or hypersensitivity reaction (with rash, fever, eosinophilia, hepatitis)

Question 8

What is the protocol for taking allopurinol?

Answer 8

◦ Can only use Allopurinol when attacks are frequent and severe or have renal impairment/tophi or when pt can’t tolerate NSAIDs or colchicine.
◦ Cannot start within 1 month of acute attack
◦ Need NSAIDs/Colchicine cover 2-4 weeks before starting Allopurinol and can stop them 4 weeks after.
◦ Start at 100mg/24h and titration increasing every 4 weeks until plasma urate levels are <300 micromol/L
*once people start allopurinol they will normally take it lifelong and cannot stop it during attacks

Question 9

What are the three types of calcium pyrophosphate deposition (CPPD)?

Answer 9

• Acute CPP crystal arthritis: like gout, causes acute monoarthropathy of typically larger joints in elderly patients (knee and wrist)
◦ Usually spontaneous and self limiting
◦ Can be provoked by illness, surgery or trauma
• Chronic CPPD: inflammatory RA like (symmetrical) polyarthritis and synovitis
• Osteoarthritis with CPPD: chronic poly articular osteoarthritis with superimposed acute CPP attacks

Question 10

What are the risk factors for CPPD?

Answer 10

• Old age
• Hyperparathyroidism
• Haemochromatosis
• Hypophosphataaemia

Question 11

What Ix do you do for CPPD?

Answer 11

• Polarised light microscopy of synovial fluid shows weakly birefringent crystals.
• X-ray: soft tissue calcium deposition
*Must exclude septic arthritis and send joint fluid for culture

Question 12

What is the Mx for CPPD?

Answer 12

• Cool packs
• Rest
• Aspiration: greatly reduces pain
• Intra-articular steroids

Question 13

What is the Rx for CPPD?

Answer 13

• Intra-articular steroids
• NSAIDs
• Colchicine (used with caution)
• Chronic CPPD: methotrexate and hydroxychloroquine can be used