gout
Meaning of gout: An arthritis caused by crystals rather than by wear, which is why it arrives overnight and can leave the joint untouched between attacks.
Definition of gout
Gout is a form of arthritis in which needle-shaped uric acid crystals form inside a joint and its surrounding tissue, provoking sudden inflammation. Attacks bring intense pain, swelling, warmth and discoloration over the joint, most classically at the base of the big toe. Crystals form when uric acid in the blood stays high enough, for long enough, to come out of solution.
Where does the uric acid come from?
Uric acid is the end product of breaking down purines, chemical units found in the body's own cells and in food. The body handles this constantly, and the kidneys clear most of what is produced. Levels rise when production outpaces clearance or, far more commonly, when the kidneys excrete too little. Kidney impairment, certain medicines including some diuretics, heavy alcohol intake, drinks sweetened with fructose, a diet rich in red meat and shellfish, and rapid cell turnover from illness or its treatment all push the balance in that direction. Inherited differences in the kidney transporters that handle urate explain much of why gout runs in families.
What happens during an attack?
Once crystals form in a joint, immune cells treat them as foreign material and mount an aggressive response. The resulting inflammation builds over hours, often starting at night, and reaches a point where the weight of a bedsheet is unbearable. An untreated attack settles over days to weeks by itself. Between attacks a person can be entirely free of symptoms, which is one reason the underlying problem is easy to ignore. Repeated attacks over years can damage cartilage and bone, and crystals can accumulate into visible lumps called tophi in tissue around joints, in the ear and in tendons. Uric acid can also crystallize in the kidney and form stones.
How is it distinguished from similar problems?
| Gout | Pseudogout | Joint infection | |
|---|---|---|---|
| Crystal involved | Uric acid | Calcium pyrophosphate | None |
| Typical site | Base of the big toe, ankle, knee | Knee, wrist | Any joint |
| Fever | Sometimes | Sometimes | Common |
Because these overlap, fluid drawn from the joint and examined for crystals and for bacteria is what settles the question. A blood uric acid level is not the deciding test, since it can be normal during an attack and raised in people who never develop gout at all.
Also known as
Used in a sentence
The patient presented with sudden pain and swelling in the big toe consistent with an acute gout flare.
Good to know
A raised blood uric acid level is not by itself a diagnosis of gout, since many people with high levels never develop attacks and the level can read normal during one, which is why joint fluid examined for crystals is the definitive test.
Word origin
Where “gout” comes from
From Old French goutte, from Latin gutta, meaning a drop, reflecting an old belief that the disease came from a harmful substance dripping into a joint.