Gout is the major clinical feature of a high blood uric acid level. Traditionally it is associated with portly upper class, port swilling men. In truth gout can affect anybody although men are much more likely to suffer from it than women and overweight is one of a number of predisposing factors.
Clinical Features of Gout
Gout can take two forms, the most well-known being acute gout. This is characterised by the affected joint becoming hot, red swollen and painful. The classical joint is the big toe joint (first metatarso-phalangeal joint) but other joints including wrists, other foot joints and hands may be affected. The patient usually feels unwell and has a temperature. The arthritis usually resolves within a few days or sometimes weeks but some may go on to develop the chronic form and have repeated attacks.
Chronic gout is characterised by high blood uric acid and sometimes associated with kidney stones and the formation of tophi – pockets of uric acid deposits in joint cartilage and the ears.
Pathology of Gout
Acute gout is a classic example of the inflammatory response. When the uric acid comes out of solution it forms crystals in one or several joints. This attracts large numbers of phagocytic white blood cells to the area in order to clear away the crystals. In doing so the white cells release a package of inflammatory mediator substances which, in addition to destroying the crystals, also damage the surrounding tissues - hence the pain, swelling and redness.
High Blood Uric Acid
Uric acid is a waste product. It is formed from the breakdown of cells: the cells of all tissues are constantly being replaced. Specifically it is the nuclear component (the DNA bit) of cells that ends up as uric acid which is soluble (just) and is excreted by the kidneys.
Some uric acid comes directly from the diet. Foods rich in protein such as red meat, kidney and liver contain a high proportion of nucleic material (purines) that is broken down to uric acid. Some wines, beers and port (so the traditional view is to some extent correct) are also high in purines.
Having a high blood uric acid level doesn't mean that you will necessarily develop gout. Neither are you bound to if you eat lots of red meat and drink port – hereditary disposition plays a part.
Many people with high blood uric acid levels never experience gout but certain conditions will make it more likely. With the uric acid just about in solution anything that further increases the concentration of uric can make it come out of solution and form crystals
Risk Factors for Gout
- Family history: inherited deficiencies in any of the components involved in the metabolism of uric acid.
- Diet: high purine intake in the diet in those predisposed.
- Drugs: some diuretics and aspirin can affect the way the kidneys deal with uric acid.
- Dehydration: excessive physical activity, alcohol consumption (which dehydrates) can increase uric acid concentration.
- Trauma including surgery: can affect fluid balance and kidney function.
- Disease: any illness that increases tissue turnover can raise uric acid levels. Cancer is an example. Thyroid disease and hypertension and kidney disease are all implicated.
Treatment of Gout
Acute gout is treated with non-steroidal anti-inflammatory drugs such as naproxen or indomethacin. Where these are contraindicated colchicine is used. Low purine diet will lessen the risk of further attacks.
In chronic gout the goal is to lower blood uric acid and keep it low. Alloprinol is commonly used as it interferes with uric acid metabolism causing less to be produced. This drug is contraindicated in acute gout since it can initially increase uric acid concentration. Other drugs such as probenecid promote the excretion of uric acid by the kidney.
Pseudogout
This is a crystal-induced arthritis like gout but the crystals are made of calcium pyrophosphate. These are shed from the cartilage that forms joints, however the reasons are not well understood. The disease presents as an inflammation of the joints, commonly the knees, wrists or shoulders. Attacks are not normally as painful as true gout.
This article is for information only. If you have any health concerns you should consult your doctor.
Resource
ABC of Rheumatology Ed. M. Snaith Pub. BMJ Publishing 2004
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