Gout

Inflammatory arthritis from monosodium urate crystal deposition secondary to chronic hyperuricemia, overproduction (rare) or underexcretion (far more common, renal, worsened by diuretics, renal impairment, alcohol).

• Acute flare: sudden severe monoarticular pain, classically first MTP (podagra, >50% of first attacks), also ankle/knee/wrist ; erythema, warmth, exquisite tenderness, peaks 12-24h, self-limits over 1-2 weeks untreated

• Intercritical gout: asymptomatic between flares

• Chronic tophaceous gout: tophi (ears, olecranon, fingers), chronic joint damage

• Triggers: alcohol (especially beer), purine-rich foods, dehydration, trauma/surgery, starting/stopping urate-lowering therapy

• Joint aspiration (gold standard): negatively birefringent needle-shaped urate crystals; excludes septic arthritis (critical: can coexist)

• Serum urate: often elevated but can be normal during acute flare; recheck when settled

• FBC, CRP/ESR: elevated during flare, non-specific

• X-ray: normal early; chronic disease; "punched-out" erosions with overhanging edges

Differentials: septic arthritis (must exclude, aspirate if any doubt), pseudogout/CPPD (positively birefringent rhomboid crystals), reactive arthritis, cellulitis, trauma, RA (tophaceous gout can mimic).

Acute flare:

• NSAIDs first-line (naproxen 500mg bd, indomethacin 50mg tds) until resolved + 48h

• Colchicine: low-dose (500mcg bd-tds), most effective within 24-36h of onset; caution with statins/macrolides (CYP3A4 interaction toxicity)

• Corticosteroids: prednisolone 30-35mg od × 3-5 days, or intra-articular injection; alternative if NSAID/colchicine contraindicated

• Do NOT start/stop ULT during a flare if already established; continue unchanged

Urate-lowering therapy; indications: ≥2 flares/year, tophi, urate arthropathy, CKD stage ≥2 with gout, urolithiasis with gout:

• Allopurinol; first-line: start LOW (100mg od, lower in renal impairment), titrate slowly (+100mg every 2-4 weeks) to target urate <6mg/dL (<5mg/dL if tophi) ; HLA-B*5801 screening in high-risk populations (Southeast Asian ancestry) before starting given severe hypersensitivity risk

• Febuxostat: alternative if allopurinol intolerant ; caution with CV disease history

• Flare prophylaxis during ULT initiation: low-dose colchicine or NSAID for 3-6 months (urate mobilization paradoxically increases flare risk)

• Lifestyle: weight loss, reduce alcohol/purine intake, hydration, switch diuretic if feasible

Referral: rheumatology for diagnostic uncertainty, refractory/tophaceous disease, frequent flares despite ULT.