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How is Behçet’s syndrome diagnosed?

Diagnosing Behçet's can take some time. There's no test to confirm the diagnosis, and the symptoms can be confused with those of other, more common illnesses. Your doctor will need to rule out other possible causes of your symptoms.

What tests are there for Behçet's syndrome?

Pathergy test

You may need to take a pathergy test. This measures the increased sensitivity of the skin that occurs in Behçet's syndrome. Your doctor will give you a small pin-prick or injection – if a characteristic red spot appears on the skin around the pin-prick, then the result is positive. This doesn't mean you definitely have Behçet's, but your doctor will take this result into account, along with your symptoms, when making the diagnosis.

A definite diagnosis isn't always possible, but you might have Behçet's if you have recurrent mouth ulcers (more than three in a 12-month period) plus any two of the following:

  • genital ulcers
  • skin problems
  • eye inflammation
  • a positive pathergy test.

Blood tests

Blood tests won't confirm a diagnosis of Behçet's, but they may be taken in order to:

  • rule out other diseases
  • measure the degree of inflammation, for example:
    • erythrocyte sedimentation rate (ESR)
    • C-reactive protein (CRP)
  • monitor the effect of drug treatments and to check they're not causing side-effects, for example:
    • full blood count
    • kidney function tests
    • liver function tests
  • test for a genetic marker (HLA-B51) – it's thought that people with this genetic marker are more likely to develop Behçet's. Its presence supports a diagnosis (although it may be found in people without Behçet's.

Parents with Behçet's syndrome sometimes ask if their children should have the HLA-B51 test to see whether they might develop the disease in the future. This isn't recommended because there's no way of knowing whether a child will develop Behçet's syndrome even if they do have this gene. If you think your child or another relative might have Behçet's syndrome, they should see their doctor and mention that there's a history of Behçet's syndrome in the family.

Additional symptoms (for example arthritis, thrombosis) may increase the likelihood that the diagnosis is correct.

Other tests

Different people may need different tests, for example:

  • You may have a chest x-ray to check there's no infection in your lungs, particularly if your doctor suggests treatment that might affect your immune system.
  • If you have bowel problems you may need a telescopic examination of the bowel or stomach (endoscopy). In some specialist centres, examination of the small bowel can be carried out using a small, pill-sized camera which is swallowed (wireless capsule endoscopy).
  • Computerised tomographic (CT) and magnetic resonance imaging (MRI) scans can give more detailed images than x-rays. These scans may be needed to look further into specific symptoms.


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