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Gout

life science Maturity 11-13 Next article →

Gout is a specific form of inflammatory arthritis. It is characterized by sudden, recurrent attacks of intense pain. These attacks cause joints to become red, tender, hot, and swollen.

Gout2010
Gout2010

This condition is a disorder of purine metabolism. It occurs when the body's final metabolite, uric acid, crystallizes into monosodium urate. These crystals then deposit in joints, tendons, and surrounding tissues. Gout affects approximately 1% to 2% of adults in the developed world. It has become more common in recent decades due to changes in diet and longer life expectancy.

The underlying cause of gout is hyperuricemia. This term describes persistently elevated levels of uric acid in the blood. In about 90% of cases, hyperuricemia is caused by the underexcretion of urate by the kidneys. In less than 10% of cases, the condition results from the overproduction of uric acid.

Harnsäure Ketoform
Harnsäure Ketoform

When uric acid levels reach a certain threshold, the substance begins to crystallize. These needle-shaped crystals precipitate into the body's tissues. This process is often triggered by factors like cool temperatures or rapid changes in uric acid levels. For example, lower body temperatures at night may explain why joint pain often begins during the night.

Once the crystals deposit, they trigger a complex biological mechanism. If the crystals are part of a walled-off deposit, they may not cause immediate trouble. However, if naked crystals break out due to physical trauma or surgery, they trigger an immune response. This reaction involves macrophages, which are specialized cells in the immune system. The process is initiated by a protein complex called the NLRP3 inflammasome. This complex activates the enzyme caspase 1. This enzyme then converts pro-interleukin 1β into active interleukin 1β. This protein is a key part of the inflammatory cascade that causes the painful swelling.

Gout can manifest in several distinct ways and locations. The most common presentation is an acute attack of inflammatory arthritis. About half of all cases involve the metatarsophalangeal joint at the base of the big toe. This specific condition is known as podagra.

Gout2010
Gout2010

Gout can also affect midfoot structures like the cuneiform bones. Other joints, including the heels, knees, wrists, and fingers, may be involved. Long-standing hyperuricemia can lead to the formation of tophi. Tophi are hard, often painless deposits of uric acid crystals.

Tophaceous gout affecting the arms and hands Wellcome L0062959
Tophaceous gout affecting the arms and hands Wellcome L0062959

Extensive tophi can eventually lead to chronic arthritis and bone erosion.

Beyond the joints, high uric acid levels can impact other systems. Crystals may precipitate in the kidneys, leading to the formation of kidney stones. This can result in acute uric acid nephropathy, which is kidney damage. The history of gout is quite long, dating back to at least the time of the ancient Egyptians. Because it was often linked to the consumption of expensive foods, it was historically called "the disease of kings" or "rich man's disease."

Many factors influence the risk of developing gout. Dietary choices account for about 12% of cases. Foods high in purines, such as liver, shellfish, anchovies, and dried mushrooms, increase risk. Alcohol consumption, especially beer and spirits, is also strongly associated with the condition. Genetics play a massive role, contributing to about 60% of the variability in uric acid levels. Specific genes like SLC2A9, SLC22A12, and ABCG2 are commonly associated with the disorder. Additionally, metabolic syndrome occurs in nearly 75% of gout cases. This syndrome includes abdominal obesity, hypertension, and insulin resistance.

Doctors use several methods to diagnose gout and manage its symptoms. A definitive diagnosis is made by identifying monosodium urate crystals in synovial fluid. This fluid is collected through a process called arthrocentesis. Under polarized light microscopy, these crystals show a needle-like shape. While blood tests can show hyperuricemia, they are not always reliable during an active attack. Treatment focuses on reducing inflammation and lowering uric acid levels. Nonsteroidal anti-inflammatory drugs (NSAIDs), glucocorticoids, or colchicine are used to improve acute symptoms. For long-term prevention, medications like allopurinol or probenecid may be prescribed.

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Tophaceous gout affecting the arms and...
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