Case report
A 56-year-old man with a history of Biermer anemia treated by vitamin B12 since one year.
He has asthma and no other illnesses, allergic diseases or reactions, especially to drugs, consulted a private gastroenterologist because of abdominal discomfort. He had no fever, and the physical examination revealed no abnormality. The patient was prescribed 40 mg of omeprazole daily. Four hours after the first dose of omeprazole, the patient developed urticarial lesions with annular erythematous wheals localized on the trunk and upper limbs. There was neither angioedema nor respiratory and hemodynamic symptoms. The patient consulted urgently his gastroenterologist who considered the condition as acute generalized urticaria to omeprazole and prescribed cetirizine and dexamethasone, commenced immediately. The urticaria has disappeared entirely after an hour. Four weeks later the patient consulted in our department for investigating this episode of urticaria. Skin prick test (20mg/mL) than intradermal tests (IDT) (0.2 and 2 mg/mL) to omeprazole were performed on the patient’s forearm according to the European Network of Drug Allergy recommendations. Histamine 10 mg/mL and 0.9% normal saline were used as positive and negative skin prick test controls, respectively. About ten minutes later, the patient had a strong reaction to omeprazole IDT 0.2 and 2 mg/mL. An IDT to omeprazole (0.2mg/ml) performed on two healthy controls according to the same procedure applied on the patient was negative. To assess cross-reactivity to other PPIs in our patient, we subsequently performed prick test to lansoprazole and IDT to esomeprazole (0.8mg/mL), and pantoprazole (0.4mg/mL) that were negative at 20-min reading. Moreover, graded oral provocation test with these drugs were carried out with negative result. OPTs with the alternative PPIs which had displayed negative results in the skin tests, were performed after his informed consent. During these tests, a lansoprazole capsule (15 mg), a pantoprazole tablet (20 mg), and an esomeprazole tablet (20 mg) were administered each on different days at 30-min intervals at increasing doses till reaching the full dose or the symptoms of a drug reaction occurred. These tests results were negative in all cases.