What does the pathergy test diagnose?

The pathergy test is a specific diagnostic tool used primarily for Behçet's disease. This condition is an autoimmune disorder characterized by recurrent oral and genital ulcers, skin lesions, and ocular inflammation. The test involves pricking the skin with a needle and observing for an exaggerated inflammatory response, typically a sterile papule or pustule forming at the site within 24 to 48 hours.

A positive pathergy test is not definitive for Behçet's disease on its own but is one of the criteria used to support the diagnosis. This test highlights the hyperreactivity of the immune system, which is a hallmark of Behçet's disease. The test is less relevant or not performed in the diagnosis of rheumatoid arthritis, systemic lupus erythematosus, or multiple sclerosis, as these conditions have different underlying pathophysiologies and do not present with the same type of exaggerated skin reactivity observed in Behçet's disease.