Gout and hyperuricaemia

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What is Gout and hyperuricaemia?

Gout is a condition in which there are deposits of a chemical (sodium urate) in joints, causing arthritis, as well as in soft tissues and the urinary tract.

Urate or uric acid is a chemical formed from the breakdown of purines - DNA building blocks derived from protein. Hyperuricaemia means that a person has too much uric acid in the blood - which is associated with gout. When uric acid precipitates in a joint (often the big toe) it causes an acute arthritis.

Uric acid can also be deposited in:

soft tissue, causing tophi (white chalky deposits) and tenosynovitis - tendon inflammation.
urinary tract, causing stones and potentially renal failure (since 2/3 of uric acid is excreted by the kidney)

Who gets Gout and hyperuricaemia?

Gout is a condition mainly seen in developed countries. It affects approximately 0.25% of Europeans. It is 10 times more common in men. It rarely occurs before puberty and more prevalent in the upper social classes.

Hyperuricaemia affects approximately 5% of the population - hence not everybody with hyperuricaemia develops gout - other factors must be important.

Predisposing Factors

One third of patients with gout have a positive family history.

Uric acid levels increase with obesity, a high protein diet, high alcohol consumption, diabetes mellitus, cholesterol, ischaemic heart disease, and hypertension.

Secondary causes of hyperuricaemia can be caused by

Impaired excretion of uric acid: chronic renal failure, thiazide diuretics, hypertension;

Increased production of uric acid: polycythaemia, leukaemia, cytotoxics, psoriasis;

An acute attack of gout may be precipitated by - surgical operation, dietary or alcoholic excess, starvation, infection or drugs (especially thiazide diuretics).

Progression

There are four clinical syndromes:

Acute urate arthritis (gout): this is the classical presentation with an acutely painful, inflamed joint (often the big toe) which resolves within a week.

Chronic polyarticular gout: involving numerous joints and gradually causing joint damage and potentially loss of function.

Chronic tophaceous gout: smooth white deposits of urate in the soft tissues.

Urate renal stone formation: urinary stones may present with acute urinary colic, and chronically can lead to kidney failure.

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