Flare up reaction during provocation test to glatiramer acetate in a patient with allergy to interferon beta1a.

Glatiramer acetate (GA) is a synthetic amino acid polymer, used for relapsing-remitting multiple sclerosis. The most common adverse effect of GA is a skin reaction at the injection site with a probable IgE-mediated mechanism. We report a case of a 45-year-old woman with multiple sclerosis and urticaria to interferon-β1a, who underwent a challenge test to GA. She presented itching wheals at the intradermal sites. A month later the patient repeated the test and presented the same reactions of the first test. The next day she continued the test with subcutaneous injections. One hour later she presented a flare up of the reactions appeared during the previous 2 tests. No reactions appeared at the subcutaneous injection sites. The patient also presented dyspnea. Flare-up reactions are characterized by the reactivation of previously positive reactions to intradermal or skin tests triggered by patch testing and after systemic provocation with an allergen. The phenomenon is not common to drugs. The mechanisms involved in this reaction seem to be heterogeneous and are not completely understood. To our knowledge this is the first case of allergic reaction to GA manifested as a flare-up reaction during challenge test.