Gout and Pseudogout
Gout is a disorder where uric acid crystals form inside joints, and this irrirates the joint, causing inflammation.
Uric acid is a natural chemical in the body that is a product of the breakdown of something called purine (which partly makes up DNA). Uric acid levels can be raised for a number of reasons. If uric acid levels are high, then the uric acid can crystalise as urate crystals – and urate crystals in a joint are irritant and cause inflammation.
The old image of a fat, port-drinking, cigar-smoking man being the typical gout sufferer really isn’t true – anyone can get gout.
The most commonly affected joint is the joint at the base of the big toe (the first metatarsophalageal joint). However, gout frequently affects knees. With an acute attack of gout the knee will become red, hot, swollen and very painful. It can be very painful to move the joint or walk.
If someone has a clear history of having previously been diagnosed with gout (either in the knee or in some other joint) then an acute attack of gout may be fairly obvious to diagnose. However, in someone with no past history of gout or in situations where any potential doubt exists, then it is important to investigate the knee properly – even if just to exclude other potential causes of a hot, painful, swollen joint, such as infection (septic arthritis).
The only definite way to confirm gout is to aspirate a sample of joint fluid from the knee. The sample is sent to the lab and is examined under polarized light microscopy. Gout crystals show up as tiny birefringent crystals.
In an acute attack of gout, blood tests normally show elevated levels of the inflammatory markers (ESR and CRP), although these can also be elevated in other conditions such as infection.
We also tend to test patients’ uric acid levels in their blood too. A raised uric acid level implies that you might have gout, but it is possible to have high uric acid levels without gout.
It is also often very useful to get proper imaging of an affected joint as well, with X-rays and also potentially an MRI scan.
Treatment of an acute attack of gout relies on the use of anti-inflammatories.
Treatment of milder cases of gout may just need simple anti-inflammatories such as Ibuprofen/Nurofen or possibly slightly stronger anti-inflammatories such as Diclofenac/Voltarol. In people who can’t take anti-inflammatories (because of stomach ulcer problems or kidney issues), Colchicine is a slightly old-fashioned drug that can be taken instead, but which is still pretty effective.
If a knee is severely swollen and painful then it can help enormously to aspirate some of the fluid off the knee (draw it off with a needle) and then some steroid/cortisone can be injected into the joint – this acts just locally in the joint as a very powerful anti-inflammatory.
If a patient has had a confirmed diagnosis of gout and if they have got over an acute attack, then Allopurinol is a drug that can be taken long-term prophylactically, to help reduce the risk of further recurrent attacks.
In the long-term, severe/repeated attacks of gout in a joint can cause damage to the articular cartilage, leading to secondary osteoarthritis – which sometimes ends up leading to the need for knee replacement surgery.
Pseudogout is in some ways similar to gout. However, it is caused by deposition in the joints of a different type of crystal – Calcium Pyrophosphate Crystals. The end result is similar to gout, in that it causes painful, hot, swollen joints which, with time, can become damaged and arthritic.
There is a partial genetic element to pseudogout, but in tends to be very common indeed in older people, and so it might just be a ‘normal’ part of wear and tear / degeneration – Pseudogout can affect about 3% of people over the age of 60, but as much as 50% of people in their 90s!
Investigation and treatment of pseudogout is similar to that for gout. The most accurate way to confirm the diagnosis is to aspirate the joint and look for crystals (but these are Calcium Pyrophosphate Crystals, rather than uric acid crystals). Treatment is based around anti-inflammatory medications. Unfortunately, unlike gout, there is no kind of preventative/prophylactic treatment for pseudo gout.