Gout (old name: podagra) is a form of arthritis caused by the accumulation of uric acid crystals (due to hyperuricemia) in joints. It is an immensely painful disease, which in most cases affects only one joint, most commonly the big toe. The patient usually suffers from two sources of pain. The crystals inside the joint cause immense pain whenever the affected area is moved. The inflammation of the tissues around the joint also causes the skin to be swollen, tender and sore even if it is slightly touched. For example, a blanket draping over the affected area would cause extreme pain.
The classical picture is of excruciating pain of sudden onset in only one joint, usually the big toe (75% of first attacks affect the first metatarsal-phalangeal joint), associated with swelling and redness.
Patients with longstanding hyperuricemia (see below) can have tophi (uric acid crystal deposits) in other tissues e.g. the helix of the ear. Uric acid stones can form as one kind of kidney stones in some occasions.
The diagnosis is generally made on a clinical basis, although tests are required to confirm the disease.
Hyperuricemia is a required feature; it is defined as a plasma urate (uric acid) level greater than 420 μmol/L (7.0 mg/dL); despite the above, high uric acid level does not necessarily mean a person will develop gout.
Other blood tests commonly performed are full blood count, electrolytes, renal function and erythrocyte sedimentation rate (ESR). This serves mainly to exclude other causes of arthritis, most notably septic arthritis.
A definitive diagnosis of gout is from light microscopy of joint fluid aspirated from the joint (this test may be difficult to perform) to demonstrate intracellular monosodium urate crystals in synovial fluid polymorphonuclear leukocytes.
Pseudogout (calcium pyrophosphate deposition disease) is very similar disease, but the crystals look differently on light microscopy and the accumulated substance is different.
Common Musculoskeletal Disorders
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