Gout (also known as podagra when it involves the big toe) is a medical condition usually characterized by recurrent attacks of acute inflammatory arthritis—a red, tender, hot, swollen joint. The metatarsal-phalangeal joint at the base of the big toe is the most commonly affected (approximately 50% of cases). However, it may also present as tophi, kidney stones, or urate nephropathy. It is caused by elevated levels of uric acid in the blood. The uric acid crystallizes, and the crystals deposit in joints, tendons, and surrounding tissues.
Clinical diagnosis may be confirmed by seeing the characteristic crystals in joint fluid. Treatment with nonsteroidal anti-inflammatory drugs (NSAIDs), steroids, or colchicine improves symptoms. Once the acute attack subsides, levels of uric acid are usually lowered via lifestyle changes, and in those with frequent attacks, allopurinol or probenecid provide long-term prevention.
Gout has become more common in recent decades, affecting about 1–2% of the Western population at some point in their lives. The increase is believed due to increasing risk factors in the population, such as metabolic syndrome, longer life expectancy and changes in diet. Gout was historically known as “the disease of kings” or “rich man’s disease”.
High levels of uric acid in the blood (hyperuricemia) is the underlying cause of gout. This can occur for a number of reasons, including diet, genetic predisposition, or underexcretion of urate, the salts of uric acid. Renal underexcretion of uric acid is the primary cause of hyperuricemia in about 90% of cases, while overproduction is the cause in less than 10%. About 10% of people with hyperuricemia develop gout at some point in their lifetimes. The risk, however, varies depending on the degree of hyperuricemia. When levels are between 415 and 530 μmol/l (7 and 8.9 mg/dl), the risk is 0.5% per year, while in those with a level greater than 535 μmol/l (9 mg/dL), the risk is 4.5% per year.
Signs and symptoms
Both lifestyle changes and medications can decrease uric acid levels. Dietary and lifestyle choices that are effective include reducing intake of food such as meat and seafood, consuming adequate vitamin C, limiting alcohol and fructose consumption, and avoiding obesity. A low-calorie diet in obese men decreased uric acid levels by 100 µmol/l (1.7 mg/dl). Vitamin C intake of 1,500 mg per day decreases the risk of gout by 45%. Coffee, but not tea, consumption is associated with a lower risk of gout. Gout may be secondary to sleep apnea via the release of purines from oxygen-starved cells. Treatment of apnea can lessen the occurrence of attacks.
The initial aim of treatment is to settle the symptoms of an acute attack. Repeated attacks can be prevented by different drugs used to reduce the serum uric acid levels. Ice applied for 20 to 30 minutes several times a day decreases pain. Options for acute treatment include nonsteroidal anti-inflammatory drugs (NSAIDs), colchicine and steroids, while options for prevention include allopurinol, febuxostat and probenecid. Lowering uric acid levels can cure the disease. Treatment of comorbidities is also important.