[A RARE COMBINATION OF DELAYED TYPE HYPERSENSITIVITY REACTIONS TO BETA-LACTAMS IN A PATIENT WITH MSSA BACTEREMIA].

INTRODUCTION: A male patient aged 81, with a history of atrial fibrillation, pacemaker implantation and hip replacement was admitted due to pneumonia. Subsequent Methicillin Sensitive Staphylococcus Aureus (MSSA) bacteremia and septic arthritis of his prosthetic joint was diagnosed, and treated with Oxacillin. Two weeks later, an exanthematous rash appeared, involving most of his body surface, evolving to blisters that dried up and led to extensive exfoliation of the skin, consistent with a delayed type hypersensitivity drug reaction. Other possible etiologies for this rash were ruled out. Antibiotic treatment was changed to Cefalexin, assuming that there is no cross reactivity between penicillins and cephalosporins, regarding late drug reactions. Thereafter, the rash subsided, but his renal function deteriorated and interstitial nephritis due to a hypersensitivity reaction to cephalosporin was diagnosed. Hypersensitivity to penicillins and other beta-lactam antibiotics is reported by 10% of the population, only 1/10 of them are verified using standardized allergic testing (1-3). Delayed type hypersensitivity to beta-lactams is more common than immediate type allergy. It evolves days and weeks following exposure to the offending drug. Late responses are classified as type II- IV hypersensitivities, type IV being the most prevalent (4-7). We present a patient who developed two distinct delayed type phenomena to two different beta lactam antibiotics during the same hospitalization. The possibility of a hypersensitivity reaction should rise in the differential diagnosis of the deteriorating patient most notably as such might be life threatening on the one hand, and reversible, after drug withdrawal, on the other hand.