Methods: A 76 years old female patient came to our allergy outpatient department for drug allergy evaluation. The patient mentioned an allergic reaction after taking a b-lactam antibiotic 20 years ago. Due to fact that the patient suffered from psychosis she could not provide us any further details considering the episode. The patient had taken other antibiotics (clarithromycin, erythromycin and metronidazole) without any problem after the incidence but never again b lactams. Initially in-vitro tests were done for the detection of specific IgE CAP-FEIA c1, c2, c5, c6, c7 and k82 which were all negative (<0.1 kU A/L) as well as measurement of total IgE (10,8 KU/l). According to the patient’s medical history, she was under haloperidol and biperiden for psychosis and she also mentioned NSAIDS allergy for which she was also been evaluated to our department. She was skin prick tested on the volar surface of her forearm to various b-lactamic antibiotics (all together PPL1:1, MDM 1:1, amoxicillin: 20mg/ml, ampicillin: 20mg/ml, cefuroxime: 2mg/ml, negative and positive control) and also had IDs to the same antibiotics.
Results: Both tests (readings in 20 min) were all negative. In 48h the patient came back because the IDs to ampicillin, amoxicillin and amoxicilin-clavulanic acid were strongly positive in all the concentrations performed (0.2, 2 and 20 mg/ml). Two days later the erythema and oedema became worse and blisters formed. Treatment with methylprednisolone per os started with gradual tapering and topical mometasone furoate cream. Fifteen days after stopping methylprednisolone atopy patch test were performed to cefuroxime, imipenem/cilastatin, meronem and aztreonam which were negative whereas the test to penicillin G (10% in petrolatum) was positive.Afterwards the patient was challenged to cefuroxime, following the protocol for delayed hypersensitivity reactions to b-lactams, without any reaction.
Conclusions: Delayed hypersensitivity to b- lactam may be a long lasting condition in contrast to immediate type which tends to disappear with time and an accurate patient’s history is very helpful.