Cephalexin-Induced Autoimmune Hemolytic Anemia: A Case Report.

Autoimmune hemolytic anemia (AIHA) is an acquired form of hemolytic anemia with several serological subtypes, including drug-induced immune hemolytic anemia (DIIHA). Due to the complex nature of diagnosis, many of the published reports rely on establishing a temporal relationship between drug exposure and symptom onset. To date, only four case reports have suggested a possible association between cephalexin and DIIHA. Here, we present a case of AIHA that occurred following exposure to cephalexin. An 85-year-old female presented with fatigue, dyspnea, and orange urine following initiation of cephalexin three days prior. The patient presented with a positive direct antibody test and a hemoglobin level of 4.7 g/dL, following 15.1 g/dL three days prior. A direct antiglobulin test was initially positive for immunoglobulin G and complement component 3, which eventually tested negative five months later. The patient required blood transfusions, intravenous immunoglobulin, and prednisone with eventual recovery and discharge. The onset of AIHA three days after starting cephalexin and its subsequent resolution following discontinuation of the drug is strongly suggestive of a diagnosis of DIIHA secondary to cephalexin. The patient tolerated other cephalosporins in the past without an immediate immune response. DIIHA is rare, and cephalexin is a seldom-implicated agent. Cephalexin can result in profound DIIHA, requiring transfusions and prolonged hospitalization when used at a typical dose. The case draws awareness to the importance of recognizing signs and symptoms of DIIHA early on so that the offending agent can be discontinued and the appropriate testing and treatment can be performed.