What is reactive arthritis?

Reactive arthritis is a kind of arthritis that comes on after particular infections – usually within 2-4 weeks of the infection. The infections that commonly cause it are:

• causes of gastro-enteritis (food-poisoning)
  i.e. Salmonella, Campylobacter, Yersinia and Shigella
• the sexually transmitted infection, Chlamydia trachomatis

Other infections can be followed by arthritis, e.g. viruses (German measles, parvovirus (the cause of slapped cheek disease in children), or other bacteria e.g. streptococci (sore throats and skin infection). However, it is best to distinguish these cases from the true reactive arthritis which follows the listed infections because they don’t cause quite the same kind of arthritis and don’t have any associated features (see below).

The joint is not infected in reactive arthritis. However, recent research suggests that the bacteria can get to the joint but don’t multiply there and can’t be cultured when fluid from the joint is tested. This has been an active area of interest and research in Cambridge.

Diagnosis.

Reactive arthritis tends to affect a small number of joints which are very inflamed (hot, swollen, painful to use) and some others to a lesser extent. Knees and ankles are favourite sites, together with stiff backs and painful heels or soles.

Along with the arthritis, and a useful way of showing the diagnosis, sites other than joints can be involved:

• eyes – conjunctivitis, usually mild and short lasting
• skin – a rash on the soles of the feet which is a kind of psoriasis, or in men a rash on the penis (this can happen even though their arthritis isn’t due to a sexually acquired infection)
• mouth – ulcers on the palate, usually not painful

These features, along with symptoms from the triggering infection, can make the diagnosis easy. However, some patients get very mild gastro-enteritis, and infection with chlamydia can be completely free of symptoms. In these cases, and in those with no eye or skin involvement, diagnosis can be difficult. Reactive arthritis should always be considered when someone develops a hot swollen joint, whilst taking care to make sure the joint itself isn’t infected or isn’t inflamed due to a disease like gout.

It’s helpful to look for evidence of an infection known to trigger reactive arthritis by culturing stool or looking for chlamydia in urine or genital swabs. The last is important not to forget because undiagnosed chlamydia is a cause of infertility and pelvic inflammatory disease in later life. In these cases the arthritis may even draw attention to an infection which could have caused considerable trouble if left untreated. So don’t be shocked if a doctor asks about your sex life when you’ve got painful joints. There is a connection!

What’s the outlook?

Reactive arthritis varies a lot in severity. The worst cases may well need to come to hospital or even be admitted, so that doctors can be sure that it is reactive arthritis and not an infected joint. Removing fluid from the joint is essential for diagnosis, and fortunately also gives the patient a lot of relief.

Reactive arthritis is usually at its worst in the first few days or weeks, and gradually improves, though some relapses are not uncommon. The speed of improvement is often frustrating to the patients who tend to be young and otherwise fit. Symptoms usually have improved a lot by 3-4 months but often take a year or more to completely get better. The good news is that about 90% of patients get completely better and then have normal undamaged joints. An unlucky 5-10% has a continuing, chronic arthritis, although this can usually be greatly helped by additional treatment.

Treatment.

When the joints are inflamed treatment with anti-inflammatory drugs (drugs like ibuprofen and more powerful alternatives) are very helpful, and once infection of the joint has been ruled out, steroids injected into the joint can make a big difference. Careful exercise to maintain movement and build up muscle will also be needed. If the arthritis is slow to settle or becomes chronic many of the drugs used for rheumatoid arthritis can be tried, with good results using sulphasalazine and methotrexate. However most people don’t need these drugs.

What about antibiotics? This seems logical since the arthritis is being triggered by infection, but unfortunately antibiotics haven’t been shown to have any benefit in speeding up the resolution of the arthritis. If a patient has chlamydia infection this definitely needs to be treated anyway, but with a short course of antibiotics (sometimes one dose). Gastro-enteritis doesn’t always need antibiotics.

Will I get it again?

Not everyone is equally likely to get reactive arthritis after one of the typical infections – in fact when lots of people are affected is an outbreak of food-poisoning only a minority get arthritis. People who have the tissue type, HLA-B27, are more susceptible to getting reactive arthritis, and are more likely to have severe symptoms or develop the chronic form. The link with B27 is interesting, because the same tissue type is very strongly associated with ankylosing spondylitis, and we believe that reactive arthritis is a kind of “cousin” of ankylosing spondylitis, along with psoriatic arthritis and the arthritis that patients with inflammatory bowel disease sometimes get. This is one of the reasons we do research on the condition even though it’s not very common.

However, even HLA-B27+ people don’t necessarily get a second bout of reactive arthritis if they’re unlucky enough to get food poisoning a second time – though it seems sensible to try to avoid food-poisoning when visiting countries where there’s a higher risk.

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