Abacavir-induced agranulocytosis in two Taiwanese patients tested HLA-B5701-negative

Abacavir, a nucleoside reverse transcriptase inhibitor, is associated with hypersensitivity reactions (ABC HSR) in 5--8% of white patients infected with HIV-1 [1,2]. Such reactions usually occur within the first 6 weeks of abacavir treatment and are characterized by multisystem involvement [2]. Discontinuing abacavir usually promptly reverses HSR, whereas subsequent rechallenge can cause rapid, severe, and even life-threatening hypotension, renal failure, and/or death [2-4]. A strong association between human leukocyte antigen (HLA) types and occurrence of ABC HSR has been demonstrated in populations mainly consisting of whites [5,6]. In addition, recent studies have shown that routine screening for HLA-B*5701 significantly reduces the incidence of ABC HSR [7--9], and the Prospective Randomized Evaluation of DNA Screening in a Clinical Trial (PREDICT-1) assessment demonstrated a 100% negative predictive value (NPV) for HLA-B*5701 with skin patch-test-confirmed ABC HSR and a 96% NPV with clinically suspected ABC HSR [10]. Here we describe two Taiwanese patients tested negative for HLA-B*5701 who developed febrile agranulocytosis after receiving abacavir.