Gout

Gout is a form of inflammatory arthritis caused by the deposition of monosodium urate crystals in joints and soft tissues when serum uric acid levels are elevated. It typically presents with sudden, severe joint pain and swelling, most commonly affecting the big toe, although any joint can be involved. Recurrent attacks can lead to chronic gout and the formation of tophi, or subcutaneous urate deposits.

Causes and risk factors: Hyperuricemia results from overproduction of uric acid, underexcretion by the kidneys, or both. Contributing factors include obesity, high-purine diets, alcohol use (especially beer), kidney disease, certain medications such as diuretics and low-dose aspirin, and genetic predisposition.

Pathophysiology and diagnosis: Urate crystals trigger an acute inflammatory response in the joint. Diagnosis is typically confirmed by joint aspiration showing needle-shaped, negatively birefringent monosodium urate crystals under polarized light. Serum uric acid levels can be elevated but may be normal during an attack. Imaging may show tophi in advanced disease or a double contour sign on ultrasound.

Management: Acute attacks are treated with NSAIDs (e.g., indomethacin), colchicine, or corticosteroids. After the acute episode, long-term urate-lowering therapy may be started to prevent future attacks, with medications such as allopurinol or febuxostat. During initiation of urate-lowering therapy, low-dose colchicine or NSAIDs may be used for flare prophylaxis. Target serum urate level is generally below 6 mg/dL (and below 5 mg/dL for those with tophi). Lifestyle modifications include reducing purine intake, limiting alcohol, maintaining hydration, and achieving a healthy weight; management of comorbid conditions is important.

Prognosis and epidemiology: With appropriate treatment, symptoms can be controlled and attacks reduced; untreated gout can cause joint damage and tophi. It is most common in middle-aged men and postmenopausal women, with risk factors including obesity, hypertension, chronic kidney disease (CKD), and certain medications.