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.