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Gout: New News on an Old Disease
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Posted on: 10/22/2009
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Did you think gout was an old disease no longer prevalent in the U.S. population? Think again! The rate of this crystal-induced arthritis is on the rise -- along with obesity, metabolic syndrome, and cardiovascular disease, which are closely linked with gout. So say rheumatologists (doctors who specialize in treating arthritic conditions) in this review article on gout.
What is gout? Basically, it's a problem with the breakdown of uric acid, a compound that forms when purine is metabolized and passed out of the body through urine. Purines are found in high concentration in meat and meat products, especially internal organs such as liver and kidney as well as some fish products. The increased intake of fructose-sweetened soft drinks has also been linked with an increased risk of gout. Plant based foods such as vegetables are generally low in purines and even eating vegetables with purine content does not contribute to this problem.
Food does account for about one-third of the body's daily uric acid load. The rest comes from mechanisms within the body that produce this compound. When it is not passed out of the body through the kidneys and intestines, just the right conditions in the body result in the formation of uric acid crystals called tophus.
It's these crystals that form in the joints causing attacks of joint pain, swelling, and even oozing of crystals from the affected joint. The big toe is a common target for crystal formation in gout, but the ear and elbow are also common sites for crystal formation. Without visible formation of crystals, doctors diagnose this problem by examining fluid taken from inflamed joints. The crystals are clearly seen when the fluid is observed under a special polarized light microscope.
Examination of the synovial (joint) fluid helps differentiate gout from pseudogout. Both conditions are types of crystal-induced arthritis. But pseudogout is not caused by improper purine metabolism. The types of crystals involved differ and the joints affected are different, too. Whereas, gout attacks the big toe most often, pseudogout shows up in the knees, wrists, and ankles and rarely affects the great toe. The diagnosis must rule out the presence of infection, which can be a hidden problem along with gout or pseudogout.
X-rays are not usually helpful in diagnosing gout. But ultrasound has been shown diagnostic as the shape of the crystals form what looks like rosary beads inside the hyaline cartilage and this is seen in the ultrasound pictures. Hyaline cartilage is one of several layers of cartilage. This layer coats the ends of the bones and is separate from the articular cartilage. Articular cartilage forms the layer that meets joint-to-joint and allows the joints to slide and glide against each other. Ultrasound studies do not replace fluid removal and examination under a microscope because ultrasound does not confirm infection.
Once the problem has been diagnosed, treatment of the acute attack is with medications such as nonsteroidal antiinflammatories (NSAIDs), colchicine, corticosteroids, and biologic therapy. Chronic cases of gout are treated using a management model that involves lifestyle changes in diet, weight loss, and exercise. Control through the use of medications such as allopurinol, febuxostat, uricosuric drugs, and/or uricases is advised.
Most likely with the exception of nonsteroidal antiinflammatories (e.g., aspirin, ibuprofen), you haven't heard of these other medications. Because they are an important part of the treatment of this condition, if you are reading this because you or someone you know has gout, a brief description might be helpful.
This first set of drugs is used in the acute phase to prevent or control damaging joint inflammation. Colchicine is actually from the autumn crocus flower. It acts to prevent inflammation in the early stages of a gouty attack. There are some side effects such as nausea, vomiting, diarrhea, and stomach pain, so it's not for everyone.
Corticosteroids are used when patients can't tolerate the colchicine or nonsteroidal antiinflammatories (NSAIDs). Anyone with compromised kidney or liver function may need to use corticosteroids for control of joint symptoms instead. These steroids can be taken by pill (oral dose) but if only one or two joints are affected, injection directly into the joint(s) can be done instead.
Patients who don't respond to these first-line drug treatments might be tried on biologic therapy (also known as biotherapy). Anti-tumor necrosis factor therapy is one form of biotherapy. But it is expensive and hasn't been studied fully, so its use is fairly limited. It is used on a case-by-case basis when all else fails.
For patients with chronic gout, medications are used to lower urate levels in the body. This treatment is called serum uric acid (SUA)-lowering therapy. It is used until the crystals dissolve. For some patients, ongoing use of these medications is necessary to maintain acceptable levels of uric acid and thereby prevent the deposit of these crystals. Allopurinol is the most commonly used SUA-lowering drug. It works by inhibiting a substance called xanthine oxidase, which then reduces the production of urate. As with all drugs, there are some patients who can't tolerate allopurinol. They develop an itchy skin rash, severe diarrhea, and fever.
Those patients who are sensitive to allopurinol can try a new SUA-lowering drug called febuxostat. This medication also inhibits xanthine oxidase but does so through a different route than allopurinol. Another class of SUA-lowering drugs called uricosuric drugs includes probenecid, sulfinpyrazone, and benzbromarone. These drugs block the transportation of urate forcing them to be spilled out in the urine. Benzbromarone isn't available everywhere as concerns about liver toxicity have resulted in the drug being removed from the market in some countries (including the United States).
And a final alternative to SUA-lowering drugs is the use of uricases. Uricases transform uric acid into something else (a molecule called allantoin) that doesn't form crystals. This drug can only be given intravenously and is used for severe cases of gout because the body makes antibodies against the uricase.
The authors conclude that both gout and pseudogout have been with us for a very long time. The first report of this crystal-linked joint disease was recorded in 2640 BC. Once called the arthritis of the rich because of diet and lifestyle, its link with obesity and sugar intake today remains an important one. Even with newer medications available, the problem has not been cured or removed and an increased number of adults now have this condition because of similar lifestyle factors.
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References:
Gregory R. Emkey, MD, and Anthony M. Reginato, MD, PhD. All About Gout and Pseudogout: Meeting a Growing Challenge. In The Journal of Musculoskeletal Medicine. October 2009. Supplement. Pp. S17-23.
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*Disclaimer:*The information contained herein is compiled from a variety of sources. It may not be complete or timely. It does not cover all diseases, physical conditions, ailments or treatments. The information should NOT be used in place of visit with your healthcare provider, nor should you disregard the advice of your health care provider because of any information you read in this topic. |
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