Gout describes a type of arthritis that is characterized by the formation of sodium urate crystals in and around joints. The condition is the most common form of inflammatory arthritis, affecting around 1.5 percent of people in the UK.
Gout is intensely painful and gout attacks often have a sudden onset and occur during the night. People with gout develop painful, hot and swollen joints and the skin across the affected area often turns shiny and starts to peel. The joint becomes extremely sensitive and even the weight of bed sheets or bedclothes can cause pain.
Gout usually affects the big toe, but the condition can also involve the wrists, fingers, knees, elbows, ankles or joints in the midfoot. When several joints are affected at the same time, the condition is referred to as polyarticular gout. Joints towards the centre of the body such as the shoulders or hips are rarely affected by gout.
The urate crsytals that form around joints can also form elsewhere in the body and may even develop underneath the skin and give rise to small, white lumps that are referred to as tophi. At this stage, the condition is often referred to as tophaceous gout. These lumps do not usually cause pain but they can rupture and released pus that contains the white, gritty urate crystals.
Gout occurs when urate builds up in the blood. Urate is a breakdown product of purines. Around two thirds of the urate comes from the purines inside the cells in our bodies and around one third comes form the foods we consume. It is healthy to have some purines in the blood and when they start to accumulate, the kidneys usually excrete any excess, which is passed out of the body via the urine.
However, in cases where the body is producing an excess of urate or the kidneys are failing to remove this substance effectively, the urate level can start to rise and eventually cause urate crystals to form in the joints. These crystals accumulate in the cartilage and eventually spill over into the joint cavity. This is referred to as crystal shedding. As the crystals make contact with the joint lining (synovium), they cause it to become inflamed. This inflammation causes the crystals to break down and depending on how many crystals have spilled into the joint, symptoms are alleviated over the next few days or weeks.
Several factors increase the likelihood of the blood uric acid level rising and gout developing. These include the following
- Male gender – Gout is more common among men than among women.
- Family history – Gout often runs in families and there may be a genetic predisposition to developing hyperuricemia and gout.
- Older age – Gout rarely occurs in children and is more common among middle-aged adults and the elderly.
- Overweight – The larger a person is, the more urate they produce each day meaning overweight or obesity can mean too much urate is produced for the kidneys to process effectively.
- Purine-rich foods – Eating foods that are rich in purines can lead to hyperuricemia and trigger gout.
- Alcohol – A high alcohol intake can increase the risk of hyperuricemia, since alcohol can interfere with urate excretion.
- Medical disorders that affect kidney function and therefore the elimination of uric acid can cause gout. Examples of conditions that can cause gout include high blood pressure, kidney disease, diabetes, underactive thyroid gland, hemolytic anemia, psoriasis, hyperlipidemia and some cancers.
- Some medications may also raise the risk of developing gout. Examples include diuretics, aspirin, niacin, cyclosporine and levodopa.
In cases where a doctor can identify what is causing the gout such as diuretic use or kidney disease, the condition is referred to as secondary gout. However, most gout occurs as a primary condition and usually arises as the result of a combination of factors such as an inherited condition that affects the kidneys along with overweight or obesity.
If a person is prone to gout, some of the factors that can trigger a gout attack include the following:
- Excess alcohol intake
- Knocking or injuring the joint