Gout Flashcards
How common is it?
Prevalence of 1.4%
Who does it affect?
Gout is more common in men 3.6:1 (30-60 years if age) and in older people. Only 3-6% of people with gout have onset of the disease before 25 years of age. May be more common in black and Maori ethnicities vs Caucasian.
What causes it?
Uric acid is the end-product of the breakdown of purines (adenine and guanine), and exists as sodium urate in extracellular fluid. Two-thirds of urate is excreted by the kidneys and a third by the GI tract.
Hyperuricaemia is the single most important risk factor for developing gout.
However, gout can occur in people with normal plasma urate levels.
Hyperuricaemia is usually due to impaired renal excretion of urate. About 90% of people with hyperuricaemia are under excretors of urate, about 10% are over-producers, and some can be both.
Gout tends to attack joints in the extremities because temperatures in the feet and hands can be low enough to precipitate urate from plasma. Thus tophi typically form in the helix of the ear, finger tips, olecranon bursae, and other cool anatomical sites.
What risk factors are there?
In many people with hyperuricaemia, the cause is multifactorial, suggested risk factors include cardiovascular disease, renal disease, diabetes mellitus, obesity, metabolic syndrome, dyslipidaemia, severe psoriasis, alcoholism, lead toxicity, and use of certain drugs (e.g. diuretics).
How does it present?
Joint swelling, redness, warmth, and pain on passive movement.
Tophi
Signs on examination?
Arthritis (swelling, redness, warmth, and pain on passive movement). The big toe is most commonly affected by gout. Other affected areas include the mid foot (‘boot lace area’), heel, ankle, knee, finger, wrist, and elbow (listed in order of decreasing frequency). Lower limb joints are affected more frequently than upper limb joints.
Tophi (firm, white, translucent nodules): It usually takes at least 10 years after the first attack of acute gout for tophi to develop. Tophi are most commonly found on fingers, toes, ulnar sides of forearms, olecranon bursae, prepatellar bursae, Schilles tendons, and the helix of the ears, but they can occur anywhere (for example the spinal cord and vocal cords), especially in older people. The pattern of tophi and joint involvement is characteristically asymmetric.
Investigations
Limited in use initially because serum uric acid level can be normal during an acute attack, especially if the person is taking urate-lowering drugs, high dose aspirin, or corticosteroids.
Treatment
NSAIDs for pain.
Allopurinol for prevention.
Febuxostat seconds line.
Urate-lowering medication is normally lifelong.
Lots of lifestyle advice. Aim for ideal bodyweight, eat sensibly, drink sensibly, avoid dehydration, consume low fat dairy products, limit consumption of sugary drinks, take regular exercise, stop smoking, vit C supplements.
Conditions that would present similarly
Septic arthritis Non-urate crystal-induced arthropathy (e.g. pseudogout). Osteoarthritis. Psoriatic arthritis reactive arthritis rheumatoid arthritis seronegative spondyloarthropathy haemochromatosis.
