What causes a gout flare?

A flare is triggered when monosodium urate crystals in or around a joint provoke an acute inflammatory response, mediated largely by the NLRP3 inflammasome and interleukin-1, producing sudden severe pain, swelling and redness.

How is gout diagnosed definitively?

The most definitive diagnosis is made by identifying monosodium urate crystals in synovial fluid under polarised-light microscopy; clinical, biochemical and imaging features support the diagnosis but crystal demonstration is the reference standard.

Is a high serum urate the same as having gout?

No. Hyperuricaemia is a necessary precondition but many people with elevated urate never develop gout; gout requires actual crystal deposition with clinical disease, which is why asymptomatic hyperuricaemia is treated as a separate question.

Gout

Gout is the most common inflammatory arthritis and results from the deposition of monosodium urate crystals in and around joints in the setting of long-standing elevated serum urate. It classically presents as recurrent, intensely painful flares — often first in the big-toe joint — and, if the urate burden is not controlled, can progress to chronic arthritis with tophi and joint damage.

Definition

Gout is a crystal arthropathy in which monosodium urate crystals deposit in joints and soft tissues as a consequence of persistent hyperuricaemia, producing recurrent acute inflammatory arthritis and, when untreated, chronic arthritis and tophus formation.

Scope

This entry covers gout as a clinical entity: its pathophysiology rooted in hyperuricaemia and urate crystal deposition, its characteristic clinical course from acute flares to chronic tophaceous disease, how it is diagnosed and classified, and its epidemiology and comorbidity associations. It summarises the structure of the evidence and guidelines around gout without giving individualised treatment instructions.

Key concepts

Hyperuricaemia and serum urate saturation threshold
Monosodium urate crystal deposition
Acute gout flare
Tophus and chronic tophaceous gout
Renal underexcretion versus urate overproduction
NLRP3 inflammasome and IL-1 mediated inflammation
Metabolic syndrome and cardiovascular comorbidity
Synovial fluid crystal identification

Mechanisms

Gout begins with sustained hyperuricaemia, most often from reduced renal (and gut) excretion of urate and, less commonly, from overproduction. When serum urate exceeds its saturation point, monosodium urate crystals form and deposit in joints, cartilage and soft tissue. These crystals are sensed by resident macrophages and activate the NLRP3 inflammasome, driving interleukin-1-mediated inflammation that produces the abrupt, self-limiting flares typical of the disease. With continued deposition, aggregates of crystals form tophi and sustain a chronic inflammatory arthritis that can erode bone and damage joints. Diagnosis is most secure when monosodium urate crystals are demonstrated in synovial fluid, classically as needle-shaped, strongly negatively birefringent crystals under polarised light.

Clinical relevance

Gout is a frequent cause of acute monoarthritis and an important differential to distinguish from septic arthritis; it is also closely linked to metabolic syndrome, chronic kidney disease and cardiovascular disease, so it sits at the intersection of rheumatology and general internal medicine. This entry describes how gout is understood, diagnosed and studied; it is educational reference material and not a source of individual diagnostic or treatment advice.

Epidemiology

Gout is the most prevalent inflammatory arthritis worldwide, and its prevalence and incidence have risen over recent decades in many regions. Risk increases with male sex, older age, higher serum urate, obesity, dietary factors, diuretic use, chronic kidney disease and genetic variation in urate transporters. Its strong associations with metabolic and cardiovascular disease are a recurring theme in its epidemiology.

History

Gout has been recognised since antiquity and was long associated with diet and affluence, but its modern understanding rests on the identification of monosodium urate crystals as the cause of the acute attack and on the elucidation of urate metabolism and renal handling. The development of polarised-light microscopy to confirm urate crystals, and later the clarification of crystal-driven inflammasome activation, placed gout on a firm pathophysiological footing, and international bodies have since issued recommendations standardising its diagnosis and management.

Debates

How should asymptomatic hyperuricaemia be regarded?: Whether and when elevated serum urate without clinical gout warrants intervention is debated, balancing the risk of progression to gout and possible comorbidity associations against the burden of treating a biochemical finding; major guidelines differ in emphasis.
What is the target-driven approach to long-term control?: There is discussion over how aggressively to pursue a defined serum-urate target through urate-lowering therapy versus a symptom-led strategy, with guideline bodies weighing the evidence differently.

Seminal works

dalbeth-2016
neogi-2011
dalbeth-2021

Frequently asked questions

What causes a gout flare?: A flare is triggered when monosodium urate crystals in or around a joint provoke an acute inflammatory response, mediated largely by the NLRP3 inflammasome and interleukin-1, producing sudden severe pain, swelling and redness.
How is gout diagnosed definitively?: The most definitive diagnosis is made by identifying monosodium urate crystals in synovial fluid under polarised-light microscopy; clinical, biochemical and imaging features support the diagnosis but crystal demonstration is the reference standard.
Is a high serum urate the same as having gout?: No. Hyperuricaemia is a necessary precondition but many people with elevated urate never develop gout; gout requires actual crystal deposition with clinical disease, which is why asymptomatic hyperuricaemia is treated as a separate question.