Gout
Gout was first described in the 4th century by Hippocrates. Gout affects approximately 1% of the British population, mostly men over 40.
There is an excess of a normal body chemical, called “urate” in the blood and tissues. After a time, crystals of urate form in and around joints. When urate crystals enter the joint, they cause inflammation.
Most patients have increased urate because the chemical is not passed into the urine efficiently enough. Gout can also be precipitated by high levels of uric acid in the diet (the classic red wine link), or by drugs eg. Diuretics (“water tablets”) or chemotherapy.
Primary gout is most likely to occur in men between 40 and 60. Acute attacks are common, and this proceeds to chronic gout if untreated.
Secondary gout is usually related to diuretic drugs, and is correspondingly seen in an older age-group, in both men and women. Acute attacks are less frequently seen.
A single joint is most commonly affected in an acute attack. The joint at the base of the big toe is affected in half of first attacks. Other common sites are the small joints of the hand, wrist, elbow, foot, ankle and knee. The pain develops over a few hours, often overnight. There may be a fever. There is intense pain in the affected joint, with redness, swelling and extreme tenderness; even bedclothes touching cannot be tolerated.
Tophi are large crystal deposits, frequently seen in the cartilage of the ear, and extensor surfaces of the fingers, elbows and feet. They are seen in chronic gout.
Investigations include a blood urate level, however this may actually be lowered during an acute attack, and should be measured between attacks.
Definitive diagnosis rests upon finding urate crystals within a sample of joint fluid.
An XRay of the affected joint is initially normal, but may show erosions after repeated attacks. As destruction proceeds, there may be secondary osteoarthritis.
Treatment
Treatment of the acute attack involves pain relief with anti-inflammatories. Attempting to lower the urate level may actually prolong the attack, and is avoided. Colchicine is sometimes useful for patients who cannot take anti-inflammatories.
Reduction of risk factors (weight loss, alcohol avoidance and stopping diuretic therapy) are important in reducing further attacks.
Allopurinol is used for patients with recurrent attacks, or joint damage
Pseudogout
Pseudogout affects the elderly, both men and women.
The main differential diagnosis of acute gout is pseudogout, and they may co-exist. Pseudogout is more likely to affect the knee, wrist, shoulder or ankle. It is the most common cause of acute arthritis in the elderly. There is usually no provoking cause, but it may occur after general illness or minor trauma. The crystals in the joint fluid are of calcium pyrophosphate.
The XRay in pseudogout may show osteoarthritis, and calcium within the cartilages, especially of the knee, the wrist, or the pelvis.