Author: Dr Amanda Oakley, Dermatologist, Hamilton, New Zealand, 2011.
What is pathergy?
Pathergy is an exaggerated skin injury occurring after minor trauma such as bump, bruise, needle stick injury. A more severe injury, such as a surgical procedure, can result in persistentulceration in a patient with pathergy. It typically occurs in patients with Behcet disease.
Pathergy at the site of blood tests in patients with Behcet disease
In the skin pathergy test, multiple pricks are made into the forearm, using a sterile needle. The pricked area is observed over the next few days. Positive pathergy tests are present if any of the following are observed at the site of the needle prick.
Red bump (papule)
The pathergy test can also be undertaken in the oral mucosa, when a needle prick can induce a mouth ulcer.
What is the significance of the pathergy test?
The test is nonspecific and insensitive but can be useful in helping make a diagnosis of the following important skin conditions in which it is often positive.