A Rare Case of Prototheca Algaemia in a Patient with Systemic Lupus Erythematosus and Recent Belimumab Infusion

Novel agents for the treatment of immune-mediated diseases such as systemic lupus erythematosus (SLE) have been increasingly used as an alternative to or in combination with conventional therapies. Belimumab, a human monoclonal antibody that inhibits B-cell activating factor (BAFF), has demonstrated efficacy in moderate-to-severe SLE with similar adverse effects when compared to other biologic agents and conventional SLE therapies. Here, we describe a woman with SLE and diabetes mellitus (DM) on immunosuppressive therapy for five years who was admitted to the hospital for pneumonia but had a complicated hospital course with multiple infections and, most notably, a nosocomial algaemia due to Prototheca wickerhamii, which was treated successfully with amphotericin B. She had recently received three belimumab infusions as an outpatient prior to admission to the hospital. To the best of our knowledge no cases of human protothecosis in patients receiving belimumab have been described in the English literature; however, unusual infections have to be considered in all patients undergoing immunosuppressive therapies who persist with fever despite conventional antimicrobials. 1. Introduction SLE is a heterogeneous disease caused by an aberrant autoimmune response that spares no organ and affects people of African, Hispanic, and Asian ancestry more than other racial or ethnic groups [1, 2]. Genetic, environmental, hormonal, and immunoregulatory factors contribute to the expression of tissue injury and clinical manifestations. Both T and B cell antigen receptor-mediated activation are altered and early signaling events are amplified [1, 3]. All B-cell subgroups contribute to the production of autoantibodies. These play an important role in the presentation of antigens and autoantigens to T cells, thus mediating tissue damage and contributing to disease expression [1]. A better understanding of the pathogenesis of immune-mediated diseases has led to the development of a new therapeutic approach to SLE, B-cell-targeted therapy. This acts through two principal mechanisms: direct killing by monoclonal antibodies specific for B-cell surface molecules CD19, CD20 (rituximab, ocrelizumab), and CD22 (epratuzumab) and attrition due to the inhibition of B-cell survival factors BLyS (belimumab) and APRIL (atacicept) [4]. Belimumab is the first targeted biological treatment that is FDA approved specifically for the treatment of SLE [5]. Previous randomized controlled trials have shown reductions in disease activity and prevention of flares [6, 7], with an acceptable safety