Type II hypersensitivity and trimethoprim-sulfamethoxazole

Abstract

Trimethoprim-sulfamethoxazole (Septra) is a widely used antibiotic world-wide.The clinical use has been increasing in the pediatric population[1]. Septra has been associated with a broad array of drug associated reactions including gastrointestinal complaints, cutaneous reactions including Stevens-Johnson syndrome and toxic epidermal necrolysisand cytopenias including immune mediated thrombocytopenia[2]. Adverse reactions occur in 6-8% of patients. In the pediatric patient hospitalized for an adverse drug reaction priorexposure to Septra is found in 75% of patients [3].In the case presented we describe a cutaneous reaction to Septra clinically consistent with a Type2 hypersensitivity reaction with associated pancytopenia. Idiosyncratic reactions such as Type 2 hypersensitivity have rarely been reported with Septra exposure.These adverse drug reactions have infrequently been reported to be fatal [4].With the increasing use of Septra for the management of community acquired methicillin resistant Staphylococcus aureus of skin and soft tissue infections [5] clinicians will need to recognize this clinical complication.