Gout

Meet the patient

A 52-year-old publican wakes at 3am convinced a dog has bitten his toe. The first metatarsophalangeal joint is red, hot, swollen and so tender that the weight of a bedsheet is unbearable. He drank a dozen pints of beer the night before, he is on a thiazide for blood pressure, and his father had "the gout". The pain reached its peak inside twelve hours.[1][5]

Two questions frame the encounter: is this septic or crystal? (only the needle will tell — aspirate before anything) and when do I start urate-lowering therapy? (not in the attack, but soon, because gout is the one arthritis you can actually cure).[3]

What gout is — the crystal disease you can cure

Gout is a common, treatable disease caused by the deposition of monosodium urate crystals in articular and non-articular structures, driven by chronic hyperuricaemia — the higher the serum urate, the greater the risk. Its global burden is rising alongside obesity and associated comorbidities, and gout remains suboptimally managed worldwide.[5][2]

The natural history unfolds in four phases: asymptomatic hyperuricaemia, acute gouty arthritis, intercritical gout, and chronic tophaceous gout. The single most important clinical insight is that gout is curable — unlike most arthritides, sustained urate-lowering dissolves crystals, stops attacks and shrinks tophi. The reason gout remains poorly controlled worldwide is undertreatment: failure to start urate-lowering, failure to titrate to target, and failure to give flare prophylaxis.[2][3]

Etymology for viva gold: gout descends from the Latin gutta, "a drop" — medieval medicine blamed a drop of morbid humour falling into the joint. Podagra, the classical first-MTP presentation, is straight Greek: pous (foot) plus agra (seizure). The metaphors are dead; the pain they described is unchanged.[1]

Classification — four phases and the 8-out-of-10 rule

Gout is classified clinically by phase (asymptomatic hyperuricaemia, acute, intercritical, chronic tophaceous) and formally by the 2015 ACR/EULAR classification criteria, used in research and when crystal identification is unavailable.[4]

[1] [6] [4]

Epidemiology — the cardiometabolic arthritis

Gout is the commonest inflammatory arthritis in men. Prevalence is 3 to 4 percent in adults in high-income countries and rising, driven by obesity, metabolic syndrome, CKD and longer survival. Male sex predominates: oestrogens are uricosuric, so gout is rare in premenopausal women and rises after the menopause. Peak onset in men is the fourth to sixth decade; in women the sixth to eighth decade, often with diuretic use, CKD or hypertension.[1][5]

[6] [7] [3] [4]

Risk factors cluster around urate overproduction or, far more commonly, urate underexcretion:[1]

• Hyperuricaemia — the central, modifiable driver; the higher the serum urate, the higher the risk.
• Metabolic: obesity, metabolic syndrome, type 2 diabetes, dyslipidaemia, hypertension — gout is now understood as a cardiometabolic disease with independent cardiovascular risk.
• Diet: high-purine foods (organ meats, red meat, shellfish, sardines, anchovies, game), beer and spirits (beer is purine-rich from yeast; alcohol suppresses urate excretion), fructose (metabolism generates AMP and raises urate). Low-fat dairy is uricosuric and protective.
• Drugs that raise urate: thiazide and loop diuretics, low-dose aspirin, cyclosporin, tacrolimus, niacin, pyrazinamide, ethambutol, lead.
• Kidney disease — underexcretion via reduced filtered load.
• High cell turnover: psoriasis, myeloproliferative disorders, malignancy, tumour lysis syndrome, haemolytic anaemia.
• Genetics: polymorphisms in urate transporters — SLC2A9 (GLUT9) and ABCG2 — explain a large share of serum-urate variance; rare X-linked enzyme defects cause severe early-onset gout (HGPRT deficiency equals Lesch-Nyhan; PRPP synthetase overactivity).
• Lead exposure — saturnine gout, classically from moonshine or occupational lead, causes underexcretion and coexists with hypertension and CKD.[1]

Pathophysiology — why humans get gout and dogs do not

Urate is the end product of purine metabolism in humans. Most mammals convert urate to allantoin via the enzyme uricase (urate oxidase), but humans (and higher apes) lost uricase during evolution, so urate accumulates. Purines are converted by xanthine oxidase (hypoxanthine to xanthine to uric acid), which is the target of allopurinol and febuxostat.[1][5]

[1]

Hyperuricaemia arises from an imbalance between production and excretion, and in over 90 percent of patients the dominant fault is renal underexcretion, not overproduction. This single fact is why allopurinol and febuxostat (which cut production) and uricosurics (which boost excretion) can both work, and why renal function and urate-raising drugs dominate the risk profile.[1]

The four-step renal handling of urate. Urate is freely filtered at the glomerulus, then handled in the proximal tubule by a choreographed sequence of transporters:[5]

1. Glomerular filtration of unbound urate.
2. Reabsorption (nearly complete) via URAT1 (SLC22A12) and GLUT9 (SLC2A9) on the apical membrane — the targets of uricosurics (probenecid, lesinurad, benzbromarone all block URAT1).
3. Secretion into the lumen via ABCG2 and NPT1 (SLC17A1).
4. Post-secretory reabsorption, again largely via URAT1 and GLUT9.[1]

[5]

Why it crystallises where it does. When serum urate is sustained above its solubility threshold, monosodium urate precipitates in joints and soft tissues — hyperuricaemia is the single most important risk factor for crystal deposition. Deposition is favoured at cool peripheral sites such as the first MTP and the ear helix, and in pre-existing osteoarthritic joints.[5]

Crystal structure and birefringence — the exam pearl that decides the diagnosis. Monosodium urate forms slender needle-shaped monohydrate crystals (2 to 10 micrometres) that are negatively birefringent under compensated polarised light — yellow when their long axis is parallel to the compensator, blue when perpendicular. This is the opposite of CPPD (pseudogout), which forms rhomboid crystals that are weakly positively birefringent (blue parallel, yellow perpendicular). The mnemonic PGYP (Piss Yellow Parallel equals Gout) encodes it precisely.[1]

The acute attack is a NLRP3-inflammasome-driven neutrophilic fire. Shed MSU crystals are phagocytosed by synovial macrophages and neutrophils, causing lysosomal rupture and activation of the NLRP3 inflammasome, which cleaves pro-caspase-1 to active caspase-1; caspase-1 cleaves pro-IL-1 beta to active IL-1 beta. IL-1 beta drives NF-kB, TNF-alpha, IL-6 and CXCL8, producing a massive neutrophil influx — the clinical red-hot joint. This is why IL-1 inhibitors (anakinra, canakinumab) work in refractory gout, and why colchicine (which disrupts microtubules and neutrophil chemotaxis) is effective.[1]

Why attacks are self-limiting: neutrophil apoptosis and clearance, apolipoprotein B and E coating of crystals (neutralising their inflammatory potential), and rising anti-inflammatory mediators (TGF-beta, alpha-1 antitrypsin). This explains the typical 3 to 14 day natural course of an untreated attack.[1]

Chronic disease: persistent deposition drives a granulomatous foreign-body reaction — macrophages and multinucleated giant cells around crystalline deposits forming tophi. Tophi secrete RANKL, activating osteoclasts and producing the characteristic punched-out erosions with overhanging sclerotic margins (the "rat-bite" / Martel sign).[1]

Clinical presentation — the most recognisable pain in medicine

The acute gout attack is one of the most recognisable presentations in medicine:[1]

• Onset: explosive, typically overnight; reaches maximum intensity within 12 to 24 hours.
• Joint: classically a monoarthritis. The first MTP (podagra) is the site in over 50 percent of first attacks. Other sites, in descending frequency: instep or midfoot, ankle, knee, wrist, fingers, elbow.
• Appearance: the joint is red, hot, swollen, shiny and exquisitely tender — the patient cannot bear a sock, shoe or bedsheet. There may be desquamation of the overlying skin as the attack resolves.
• Systemic: low-grade fever and malaise in severe attacks; high fever should raise concern about sepsis.
• Triggers: alcohol binges (especially beer), dietary excess of purine-rich foods, dehydration or fasting, intercurrent illness, surgery or trauma, starting a urate-lowering drug (mobilisation flare), and diuretic change.[1]

The intercritical period is asymptomatic; left untreated, attacks become more frequent, last longer, involve more joints and may no longer fully remit, merging into chronic gout.[1]

Chronic tophaceous gout presents with firm, yellow-white, subcutaneous nodules (tophi) in characteristic sites: the helix and antihelix of the ear, olecranon bursa and ulnar surface of the forearm, Achilles tendon, finger pads and extensor surfaces of the fingers, and Heberden nodes of the hands in elderly women. Tophi can ulcerate, discharge chalky material, deform joints and mimic rheumatoid nodules or xanthomata.[1]

Atypical presentations:[1]

• Elderly women — often on thiazides, with polyarticular, Heberden-node involvement and hand osteoarthritis as a substrate; less dramatic inflammation.
• Organ transplant recipients — cyclosporin or tacrolimus cause aggressive, early, polyarticular tophaceous gout, often within months of transplantation.
• CKD patients — attenuated inflammation, atypical joints, restricted drug options.
• Immunocompromised — the inflammatory response may be blunted, so do not be falsely reassured.[1]

Bursitis and enthesitis: olecranon and prepatellar bursitis, Achilles tenosynovitis and enthesitis can all be gouty and should be aspirated.[1]

Differential diagnosis — aspirate first, always

The pivotal decisions are two: exclude sepsis in any acutely hot joint, and distinguish gout from pseudogout by crystal analysis. Aspirate any acutely hot swollen joint.[1][5]

[4] [6]

Other considerations: trauma or haemarthrosis (history; bloody synovial fluid), cellulitis or erysipelas (skin predominant, no joint effusion), acute calcific periarthritis (shoulder; hydroxyapatite crystals, non-birefringent), and palindromic rheumatism (recurrent short-lived flits of arthritis).[1]

Clinical and bedside assessment

A focused joint and systemic assessment:[1]

• The affected joint: redness, swelling, warmth, severe tenderness, restricted and painful active and passive movement. Compare with the contralateral joint. Palpate for an effusion (patellar tap, ballottement).
• Tophi: examine the helix and antihelix of the ear, olecranon bursa, Achilles tendon, extensor finger surfaces, finger pads, ulnar forearm. Tophi are firm, mobile or fixed, yellow-white, and may discharge chalky material.
• Screen for the metabolic syndrome: BMI and waist circumference, blood pressure, signs of dyslipidaemia (xanthelasma, arcus), evidence of diabetes, and check for psoriasis (coexists and complicates the differential).
• Drug review — this is decisive: identify thiazide and loop diuretics, low-dose aspirin, cyclosporin, tacrolimus, niacin, pyrazinamide, ethambutol, and any allopurinol, febuxostat, azathioprine or colchicine the patient may already take.
• Cardiovascular risk assessment — gout is an independent cardiovascular risk factor; calculate a risk score and assess for ischaemic heart disease.
• Fluid status and renal assessment — for diuretic decisions and drug dosing.[1]

Investigations — the crystal is the diagnosis

The definitive investigation is synovial fluid crystal analysis. Always aspirate any acutely hot swollen joint.[1][4]

Synovial fluid:[1]

• Polarised-light microscopy — needle-shaped, negatively birefringent monosodium urate crystals, often intracellular within neutrophils during an acute attack. This confirms gout.
• Cell count — inflammatory, typically 15,000 to 50,000 cells per cubic millimetre, neutrophil-predominant.
• Gram stain and culture — mandatory on every sample to exclude septic arthritis; crystals present do not exclude coexisting sepsis.[1]

Blood tests:[1]

• Serum urate — can be normal during an acute attack: 39.8 percent of gout patients in one cohort were normouricaemic at the time of the flare. Never use a single acutely-drawn urate to exclude gout — repeat it after the attack settles.[12]
• FBC, CRP and ESR — raised neutrophils and inflammatory markers in acute attacks (helps distinguish from non-inflammatory arthritides but does not distinguish gout from sepsis).
• U&E, creatinine and eGFR — renal function governs every drug choice (allopurinol start dose, colchicine dose, NSAID safety, uricosuric eligibility).
• LFTs, fasting glucose, HbA1c and lipid profile — metabolic syndrome and cardiovascular risk screen.
• 24-hour urinary uric acid (on a normal diet) — helps separate overproduction from underexcretion when selecting therapy, and was an enrolment criterion (urate overproduction) in trials of allopurinol initiation.[17]

Imaging:[1]

• X-ray — normal in early gout; in chronic disease shows punched-out erosions with overhanging sclerotic margins ("rat-bite" / Martel sign), soft-tissue tophi, and relative preservation of joint space until late (distinguishing from OA or RA).
• Ultrasound — the double-contour sign (an irregular hyperechoic band of urate on hyaline cartilage, non-floating) and synovial tophi; useful when aspiration fails or in intercritical gout.
• Dual-energy CT (DECT) — colour-codes urate deposits (green) against calcium (red), detecting subclinical tophi non-invasively.[1]

Diagnostic accuracy and the test hierarchy. Synovial fluid crystal identification is the gold standard — the 2015 ACR/EULAR criteria were built against it, with sensitivity 92 percent and specificity 89 percent. A normal serum urate during an acute attack does not exclude gout — in one cohort of 221 gout patients, 39.8 percent were normouricaemic during the flare itself. Always repeat the serum urate after the flare settles.[4][12]

[6] [12] [4] [7]

Self-test: a 58-year-old man has an acutely hot swollen first MTP and a serum urate of 5.2 mg/dL drawn in the ED. Does this exclude gout?

No. In one cohort of 221 gout patients, 39.8 percent — about two in five — had a normal serum urate during the acute attack itself. Aspirate the joint for crystals (and culture to exclude sepsis), and repeat the serum urate after the attack settles. The diagnosis rests on crystal identification, not on a single urate level.[12]

[12]

2015 ACR/EULAR classification criteria (used when crystal identification is unavailable): entry criterion equals at least one swollen joint; sufficient criterion equals MSU crystals in synovial fluid or a tophus. Otherwise score across clinical (joint pattern, time-to-peak under 24 hours, tophi, erythema, number of attacks), laboratory (serum urate) and imaging (double-contour sign or tophi on ultrasound; urate on DECT) domains; a total score of at least 8 classifies as gout.[4]

Management — the acute attack: aspirate, exclude sepsis, treat pain

[3] [6]

Gout is rarely a true resuscitation emergency, but two principles apply acutely:[3]

1. Exclude sepsis — any acutely hot swollen joint must be aspirated and cultured. If septic arthritis is suspected, start empirical intravenous antibiotics per your local septic-arthritis policy and arrange urgent orthopaedic washout without waiting for crystal results — crystals present do not exclude sepsis.
2. Relieve pain promptly — begin an NSAID, low-dose colchicine or glucocorticoid; the colchicine evidence base is in flares treated early after onset, and colchicine, NSAIDs and glucocorticoids are all strongly recommended first-line. Ice and joint rest help.
3. Identify and treat acute triggers — sepsis, dehydration, acute kidney injury, or a recent drug change.[3][7]

Management — definitive: the acute attack and long-term urate-lowering

Management splits into (A) treatment of the acute attack and (B) long-term urate-lowering therapy (ULT) with flare prophylaxis.[2][3]

A. Acute attack — first-line options of comparable efficacy, chosen by comorbidity, started as early as possible:[3][9]

• Oral NSAID at anti-inflammatory dose (with gastroprotection if indicated) — continue until symptoms settle. Avoid in CKD, heart failure, active peptic ulcer, anticoagulation and significant cardiovascular disease. In a 416-patient randomised equivalence trial, an NSAID (indomethacin) and oral prednisolone had similar analgesic effectiveness, with fewer minor adverse events on prednisolone during the first days (6 vs 19 percent).[3][9]
• Low-dose colchicine — the AGREE trial regimen: 1.8 mg total over one hour, which matched the efficacy of high-dose colchicine (4.8 mg over 6 hours) with a safety profile indistinguishable from placebo; high-dose colchicine added only diarrhoea and vomiting (76.9 percent diarrhoea vs 23 percent low-dose). Most effective when taken early in the flare. Dose-reduce in renal impairment; beware P-glycoprotein and CYP3A4 interactions (clarithromycin, ciclosporin, statins).[7][8]
• Corticosteroid — oral, intra-articular or intramuscular glucocorticoids are strongly recommended for the flare; oral prednisolone was equivalent to indomethacin in the equivalence trial above and is a safe, effective first-line option. Preferred when NSAIDs are contraindicated (CKD, heart failure).[3][9]
• IL-1 inhibitor — in patients with frequent flares and contraindications to colchicine, NSAIDs and corticosteroids, an interleukin-1 blocker should be considered.[6]

[3] [7] [8] [13]

B. Long-term urate-lowering therapy (ULT) — ACR strongly recommends initiating ULT for:[3]

• tophaceous gout, OR
• radiographic damage due to gout, OR
• frequent gout flares — and EULAR adds that ULT should be considered from the first presentation of the disease.[3][6]

ULT first-line: allopurinol (xanthine oxidase inhibitor):[3][6]

• Start LOW: 100 mg daily or less — and lower still in CKD (ACR 2020 strong recommendation).
• Titrate to target — increase the dose, guided by serial serum urate measurements, to a target below 6 mg/dL (360 micromol/L); EULAR sets below 5 mg/dL (300 micromol/L) for severe gout.
• Allopurinol is the preferred first-line ULT, including in moderate-to-severe CKD — the 2020 ACR guideline endorses it across CKD stages with a low start, and EULAR adds that the dose should be adjusted according to renal function; better understanding of allopurinol hypersensitivity risk now supports well-tolerated use in CKD.
• Screen HLA-B*5801 before starting in high-risk ancestries — the allele detects allopurinol-induced SJS/TEN with 80 to 100 percent sensitivity in Korean, Thai and Han Chinese populations (about 50 to 60 percent in Europeans), so screening is most valuable where allele frequency is at least 5 percent; if positive, choose an alternative.[3][6][2][14]

[3] [6] [14] [16] [13] [17]

ULT alternatives:[6]

• Febuxostat (non-purine xanthine oxidase inhibitor) — the ACR recommends a low starting dose (under 40 mg/day); EULAR positions it after allopurinol when the urate target cannot be achieved. Cardiovascular caution: in the CARES trial (6190 patients with gout and cardiovascular disease), febuxostat was non-inferior to allopurinol for the composite cardiovascular endpoint but all-cause mortality (hazard ratio 1.22) and cardiovascular mortality were higher. Useful when allopurinol is not tolerated or is contraindicated (e.g. HLA-B*5801-positive).[3][6][10]
• Uricosurics — EULAR: if the serum urate target cannot be achieved with allopurinol, consider febuxostat, a uricosuric, or a xanthine oxidase inhibitor combined with a uricosuric. Probenecid increases renal urate excretion; benzbromarone is potent but hepatotoxic.[6]
• Pegloticase — PEGylated recombinant uricase for refractory gout (EULAR). In the MIRROR randomised trial, pegloticase 8 mg every 2 weeks plus oral methotrexate 15 mg weekly raised the response rate at month 6 to 71.0 percent versus 38.5 percent with pegloticase plus placebo, with fewer infusion reactions and less immunogenicity — methotrexate co-therapy is now standard with pegloticase.[6][15]

C. Flare prophylaxis when initiating ULT — the ACR strongly recommends concomitant anti-inflammatory prophylaxis for at least 3 to 6 months; in the pooled phase-III analysis, prophylaxis with low-dose colchicine (0.6 mg daily) or naproxen (250 mg twice daily) for up to 6 months beat 8 weeks of prophylaxis — flares rose to 40 percent when 8-week prophylaxis stopped, versus 3 to 5 percent on 6-month prophylaxis.[3][13]

Two rules that are non-negotiable:[6][17]

1. Do not interrupt ULT for an acute attack — a small randomised trial found starting allopurinol during an acute treated flare did not prolong it; if the patient is already on allopurinol, continue it and treat the flare.
2. Treat to a target — serum urate below 6 mg/dL (360 micromol/L) generally, below 5 mg/dL (300 micromol/L) in severe gout, with dose titration guided by serial serum urate measurement; patients whose mean post-baseline urate stayed below 6 mg/dL had fewer flares than those above it.[17][6][13]

D. Lifestyle and comorbidity management (address in every patient):[2][6]

• Lose weight; limit alcohol; reduce purine-rich foods; avoid fructose-sweetened drinks; encourage adequate hydration and low-fat dairy.
• Review drugs and comorbidities: genetic factors and obesity are prominent contributors to hyperuricaemia and gout, while dietary factors contribute less variance in serum urate than once thought — so treat the cardiometabolic cluster, not just the diet; stop or switch urate-raising diuretics where the indication allows, and review low-dose aspirin against its cardiovascular indication.[2][6]

The named subtypes and scenarios

• Acute gouty arthritis — monoarticular, oligoarticular or polyarticular (polyarticular more common in chronic disease and transplant recipients).
• Intercritical gout — asymptomatic; attacks increase in frequency and duration without ULT.
• Chronic tophaceous gout — tophi, erosive arthritis, deformity; treat aggressively to a serum urate below 5 mg/dL (300 micromol/L) to dissolve deposits.
• Gouty nephropathy — three distinct renal patterns: (1) chronic urate nephropathy — medullary interstitial urate deposition with giant-cell reaction, slowly progressive CKD (the commonest pattern); (2) acute uric acid nephropathy — massive intratubular uric acid precipitation causing obstructive AKI, classically in tumour lysis syndrome; prevent with hydration, rasburicase or allopurinol before cytotoxic therapy; (3) uric acid urolithiasis — radiolucent stones in acidic concentrated urine.[5]
• Saturnine gout — chronic lead exposure (occupational, or moonshine); causes urate underexcretion and coexists with hypertension and CKD; consider a blood lead level and EDTA chelation in confirmed exposure.
• Lesch-Nyhan syndrome — complete HPRT deficiency (X-linked recessive); presents in boyhood with self-mutilation (lip or finger biting), choreoathetosis, intellectual disability, macrocytic anaemia and severe hyperuricaemia with gout and uric acid stones. Allopurinol reduces urate but does not improve the neurological disease.
• Transplant gout — cyclosporin or tacrolimus cause aggressive, early, tophaceous gout. Avoid NSAIDs (transplant kidney); prefer colchicine and steroids for flares. Never combine allopurinol with azathioprine — xanthine oxidase inhibition raises thiopurine metabolite levels and causes myelosuppression; allopurinol co-prescription requires a thiopurine dose reduction, and febuxostat labelling contraindicates the combination outright — switching azathioprine to mycophenolate avoids the interaction.[16]

Complications and pitfalls

• Joint destruction and disability in untreated chronic tophaceous gout; tophi can ulcerate, discharge and become infected.
• Recurrent flares with increasing frequency, duration and joint count without ULT.
• Urate nephropathy and uric acid stones — chronic kidney disease progression.
• Increased cardiovascular morbidity and mortality — gout is an independent risk factor for myocardial infarction and stroke; treat cardiometabolic risk aggressively.
• Allopurinol hypersensitivity syndrome (DRESS, Stevens-Johnson, TEN) — rash, fever, eosinophilia, hepatic and renal dysfunction; allopurinol is the leading cause of TEN/SJS in many countries. The HLA-B*5801 marker is relevant across populations — with 80 to 100 percent sensitivity in Korean, Thai and Han Chinese carriers versus about 50 to 60 percent in Europeans — so screen before starting where allele frequency is at least 5 percent.[14]
• Febuxostat cardiovascular caution — in the CARES trial (gout with established cardiovascular disease), febuxostat was non-inferior for the composite cardiovascular endpoint but showed higher all-cause mortality (hazard ratio 1.22) and cardiovascular mortality than allopurinol; the FAST trial in patients aged 60 or older with cardiovascular risk factors found no excess death or serious adverse events.[10][11]
• NSAID and colchicine toxicity — renal injury, gastrointestinal bleeding, fluid retention; colchicine neuromyotoxicity and myelosuppression, especially in CKD, with statins or with P-gp/CYP3A4 inhibitors.[8]
• The azathioprine-allopurinol interaction — myelosuppression; reduce the azathioprine dose substantially or switch to mycophenolate.[16]
• Frequent mobilisation flares if ULT is started without prophylaxis — flares rose to 40 percent when 8-week prophylaxis stopped in the pooled trial analysis.[13]
• The pitfall: diagnosing "gout" on a single acutely-drawn serum urate (which is normal in about 40 percent of flares) — repeat it after the attack settles.[12]

Prognosis and disposition

Gout has an excellent prognosis with treat-to-target ULT — tophi dissolve, flares cease and joint damage halts once serum urate is sustained below target. Untreated, gout progresses to chronic tophaceous destructive arthritis, accelerated CKD and increased cardiovascular mortality. Adherence to ULT is the single biggest determinant of long-term outcome; serum urate is the biomarker to follow at every visit. Most acute attacks are managed in the community; admit for suspected sepsis, polyarticular disease needing parenteral therapy, systemic illness, or social isolation. Refer to rheumatology for refractory or tophaceous gout, recurrent flares despite ULT, or for pegloticase.[3][5]

The trap is the opposite of cure: allopurinol started but never titrated above the starting dose ("allopurinol 100 mg forever"), which leaves the patient urate-high, still flaring, and wrongly labelled as "treatment-resistant" — the guideline answer is titration guided by serial serum urate to target. Long-term urate-lowering dissolves monosodium urate crystals, preventing flares and tophi; the best real-world results come from nurse-led gout services, which lead to major improvements in patient outcomes.[3][5]

Special populations

• Chronic kidney disease — allopurinol remains the preferred first-line ULT even in moderate-to-severe CKD (ACR strong recommendation), started at 100 mg/day or lower and titrated with the dose adjusted according to renal function; avoid NSAIDs; dose-reduce colchicine; there is improved understanding of well-tolerated allopurinol use in CKD.[3][6][2]
• Pregnancy and breastfeeding — gout is rare; when an anti-inflammatory is needed in pregnancy, oral, intra-articular or intramuscular glucocorticoids are the recommended class to fall back on.[3]
• Elderly — atypical, often polyarticular; renal impairment and polypharmacy favour corticosteroid or low-dose colchicine choices; review the drug list for diuretics.[8]
• Organ transplant recipients — cyclosporin or tacrolimus-induced; avoid NSAIDs (transplant kidney); prefer colchicine and steroids; the thiopurine interaction means azathioprine must be dose-reduced with allopurinol — or switched to mycophenolate — and febuxostat is contraindicated with thiopurines outright.[16]
• HLA-B*5801 carriers — screen populations with higher (at least 5 percent) allele frequency — Korean, Thai, Han Chinese — before allopurinol; if positive, use an alternative such as febuxostat.[14]
• Anticoagulated or heart failure — avoid NSAIDs; prefer colchicine (check interactions) or glucocorticoid.[3]
• Diabetes and metabolic syndrome — address the cardiometabolic cluster: obesity and genetics are the prominent contributors to hyperuricaemia, and gout's comorbidity burden drives mortality.[2]

Evidence, guidelines and regional differences

• ACR 2020 Guideline for the Management of Gout (FitzGerald et al) — strong recommendations to initiate ULT for tophaceous gout, radiographic damage or frequent flares; allopurinol preferred first-line ULT including moderate-to-severe CKD; low starting dose (100 mg/day or less, lower in CKD) or febuxostat under 40 mg/day; treat-to-target with dose titration guided by serial serum urate, target below 6 mg/dL; anti-inflammatory prophylaxis for at least 3-6 months when starting ULT; flares treated with colchicine, NSAIDs or glucocorticoids (oral, intra-articular, intramuscular).[3]
• EULAR 2016 recommendations (Richette et al) — flare treatment with colchicine, NSAIDs, oral or intra-articular steroids (or combination); IL-1 blocker when these are contraindicated; ULT considered from the first presentation; targets below 6 mg/dL (360 µmol/L) and below 5 mg/dL (300 µmol/L) in severe gout; allopurinol first-line with dose adjusted to renal function; pegloticase for refractory gout.[6]
• 2015 ACR/EULAR classification criteria (Neogi et al) — entry criterion of at least one episode of peripheral joint/bursal swelling; MSU crystals or tophus sufficient; clinical, laboratory and imaging domains (ultrasound double-contour sign, urate on dual-energy CT); sensitivity 92 percent, specificity 89 percent.[4]
• CARES trial (White et al, NEJM 2018) — in gout with cardiovascular disease, febuxostat was non-inferior for the composite CV endpoint but all-cause mortality (HR 1.22) and cardiovascular mortality were higher than allopurinol. FAST (Mackenzie et al, Lancet 2020) — in 6128 patients aged 60 or older with at least one additional cardiovascular risk factor, febuxostat was non-inferior and not associated with increased risk of death or serious adverse events.[10][11]

[10] [11]

• When to start ULT — ACR: strongly indicated for tophi, radiographic damage or frequent flares; EULAR: consider from the first presentation of the disease; a small randomised trial showed starting allopurinol during an acute treated attack did not prolong the flare.
• Controversies: the timing of ULT initiation around the first attack; the place of febuxostat given the CARES mortality signal versus the reassuring FAST trial; the role of nurse-led gout care (effective, with major improvements in patient outcomes).[3][6][17][5]

The mantra, and the pearls that decide the answer

[12] [3] [16] [14]

The mantra: aspirate the hot joint, needle-shaped MSU crystals on the scope, allopurinol low and titrated to a urate under six — gout is the one arthritis you can cure.[4][3][6]

The pearls that decide a gout answer:[3]

1. "MSU crystals in synovial fluid or a tophus are sufficient for diagnosis — needle-shaped, negatively birefringent."[4]
2. "Podagra — the first MTP — is the classical presenting joint of gout."[5]
3. "Acute attack: colchicine, NSAID or glucocorticoid — all strongly recommended first-line, chosen by comorbidity."[3][6]
4. "Allopurinol is first-line ULT, started low and titrated by serial serum urate to below 6 mg/dL, with at least 3-6 months of prophylaxis."[3]
5. "Serum urate can be normal during an acute attack (39.8 percent of one cohort) — do not use it to exclude gout."[12]
6. "Screen HLA-B*5801 before allopurinol in Korean, Thai and Han Chinese patients — sensitivity 80 to 100 percent."[14]
7. "Never combine allopurinol with azathioprine without a major thiopurine dose reduction; febuxostat labelling contraindicates the combination."[16]

Ward-round test — three stems, thirty seconds each

Stem 1 — the publican from the top of the topic (answer)

The 52-year-old publican with explosive first-MTP pain at 3am, a dozen pints of beer the night before, on a thiazide. What is your first move and your first drug? Model: Aspirate the joint before anything else — send synovial fluid for polarised-light microscopy (needle-shaped, negatively birefringent MSU crystals), cell count, Gram stain and culture. Exclude sepsis first: if the Gram stain or cell count is septic-range, start IV antibiotics and arrange washout. If it is gout (the likely answer here), start an anti-inflammatory early: an NSAID with gastroprotection if renal and cardiac function are normal, or an oral glucocorticoid if he has CKD or cardiovascular disease — the two were equivalent for pain in a randomised trial. Plan ULT (allopurinol low and titrated with prophylaxis) — a small trial found starting it during the treated attack did not prolong the flare — and review the thiazide.[3][9][17]

Stem 2 — the normal urate trap (answer)

A 58-year-old man has an acutely hot swollen first MTP. The ED serum urate is 5.2 mg/dL. The registrar says "not gout, the urate is normal". What do you say? Model: Wrong. In one cohort of 221 gout patients, 39.8 percent had a normal serum urate during the acute attack itself. Aspirate the joint for crystals (and culture to exclude sepsis), and repeat the serum urate after the attack settles. The diagnosis rests on crystal identification, not on a single urate level drawn in the ED.[12]

Stem 3 — the allopurinol-azathioprine interaction (answer)

A 62-year-old renal transplant recipient on azathioprine develops tophaceous gout. The registrar starts allopurinol 100 mg daily. What is wrong? Model: Never combine allopurinol with azathioprine — xanthine oxidase inhibition raises thiopurine active metabolite concentrations and causes myelosuppression; allopurinol co-prescription requires a thiopurine dose reduction, and febuxostat labelling contraindicates concomitant thiopurines outright. The fix: switch azathioprine to mycophenolate mofetil (the usual transplant choice) or substantially reduce the azathioprine dose with close FBC monitoring. This is the single most dangerous drug interaction in gout management.[16]

References

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3. [3]FitzGerald JD, Dalbeth N, Mikuls T, et al. 2020 American College of Rheumatology Guideline for the Management of Gout Arthritis Rheumatol, 2020.PMID 32390306
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12. [12]Lee JS, Kwon OC, Oh JS, et al. Clinical features and recurrent attack in gout patients according to serum urate levels during an acute attack Korean J Intern Med, 2020.PMID 30685959
13. [13]Wortmann RL, Macdonald PA, Fox R, et al. Effect of prophylaxis on gout flares after the initiation of urate-lowering therapy: analysis of data from three phase III trials Clin Ther, 2010.PMID 21353107
14. [14]Yu KH, Chou YH, Luo JC, et al. Diagnostic utility of HLA-B*5801 screening in severe allopurinol hypersensitivity syndrome: an updated systematic review and meta-analysis Int J Rheum Dis, 2017.PMID 28857441
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16. [16]Logan JK, Gruber JM, Grimsley EW, et al. Drug interaction between febuxostat and thiopurine antimetabolites: a review of the FDA adverse event reporting system and medical literature Pharmacotherapy, 2020.PMID 31885095
17. [17]Hill EM, Koreck A, Manthey BA, et al. Does starting allopurinol prolong acute treated gout? A randomized clinical trial J Clin Rheumatol, 2015.PMID 25807090