Gout
Also known as gouty arthritis, gout is a metabolic disease marked by urate deposits in the joints, which cause painfully arthritic joints. It can strike any joint but favors those in the feet and legs. Primary gout usually occurs in men older than age 30 and in postmenopausal women. Secondary gout occurs in older people.
Gout follows an intermittent course and commonly leaves patients free from symptoms for years between attacks. Gout can lead to chronic disability or incapacitation and, rarely, severe hypertension and progressive renal disease. The prognosis is good with treatment.
Causes
Although the exact cause of primary gout remains unknown, it seems linked to a genetic defect in purine metabolism, which causes overproduction of uric acid (hyperuricemia), retention of uric acid, or both.
In secondary gout, which develops during the course of another disease (such as obesity, diabetes mellitus, hypertension, sickle cell anemia, and renal disease), hyperuricemia results from the breakdown of nucleic acid.
Secondary gout can also follow drug therapy, especially the use of hydrochlorothiazide or pyrazinamide, which interferes with urate excretion. An increased concentration of uric acid leads to urate deposits, called tophi, in joints or tissues, causing local necrosis or fibrosis.
Pseudogout
Another condition—pseudogout—results when calcium pyrophosphate crystals collect in the periarticular joint structures. (See Pseudogout, page 348.)
Signs and symptoms
Gout develops in four stages: asymptomatic, acute, intercritical, and chronic.
Asymptomatic stage
In asymptomatic gout, serum urate levels rise but produce no symptoms.
Acute stage
As the disease progresses, it may cause hypertension or nephrolithiasis, with severe back pain. The first acute attack strikes suddenly and peaks quickly. Although it generally involves only one or a few joints, this initial attack is extremely painful. Affected joints appear hot, tender, inflamed, dusky red, or cyanotic.
The metatarsophalangeal joint of the great toe usually becomes inflamed first (podagra), followed by the instep, ankle, heel, knee, or wrist joints. A low-grade fever is sometimes present. Mild acute attacks commonly subside quickly but recur at irregular intervals. Severe attacks may persist for days or weeks.
Pseudogout
Also called calcium pyrophosphate disease, pseudogout results when calcium pyrophosphate crystals collect in periarticular joint structures. Without treatment, it leads to permanent joint damage in about one-half of the patients it affects, most of whom are elderly.
