117 CASE REPORTS One case of toxic epidermal necrolysis after treatment with belimumab in a patient with systemic lupus erythematosus Madalina Duna 1 , Dinu Valentin Balanescu 1 , Cristina Iosif 2 , Narcis Copca 3 , Denisa Predeteanu 1 , Ruxandra Ionescu 1 1 Department of Internal Medicine and Rheumatology, Sfanta Maria Clinical Hospital, Bucharest, Romania 2 Department of Pathology, Sfanta Maria Clinical Hospital, Bucharest, Romania 3 Department of Surgery, Sfanta Maria Clinical Hospital, Bucharest, Romania ABSTRACT Belimumab is a human immunoglobulin G1-lambda-1 (IgG1-λ) monoclonal antibody that targets the soluble BLyS human protein, also known as B-cell activating factor (BAFF) approved for the treatment of systemic lupus ery- thematosus (SLE). Serious and sometimes fatal infections have been reported in patients receiving novel immu- nosuppressive agents, including belimumab. Thus, physicians should exercise caution when considering belim- umab in patients with SLE. A 50-year-old woman with SLE presented with a severe, diffuse rash two months after initiating treatment with belimumab. A skin biopsy revealed epidermal necrolysis with keratinocyte detachment and apoptosis in the basal layer of the epidermis, suggestive for toxic epidermal necrolysis (TEN). Belimumab was discontinued and 500 mg of pulse IV methylprednisolone therapy every day for 3 days were administered, with resolution of the skin lesions in the following days. To the best of our knowledge, this is the first case of belimumab-associated TEN. Keywords: systemic lupus erythematosus, autoimmune disease, toxic epidermal necrolysis, belimumab Corresponding author: Madalina Duna, MD E-mail: madalina.duna@yahoo.com Romanian JouRnal of Rheumatology – Volume XXViii, no. 3, 2019 IntroductIon Systemic lupus erythematosus (SLE) is a chronic autoimmune disease affecting multiple organs, with a variable severity that can range from mild to life- threatening (1). People with SLE that receive proper treatment and preventive strategies for complica- tions can have a significantly improved function, disease course, and quality of life (2). The treatment of SLE consists primarily of immunosuppressive drugs, most often hydroxychloroquine and cortico- steroids. Both the European Medicines Agency (4) and the United States Food and Drug Administration (FDA) (3) approved belimumab for the treatment of SLE in 2011, thus becoming the first targeted thera- py for this disease. Before belimumab, the last drug to be approved by the FDA for the treatment of SLE was hydroxychloroquine in 1955 (5). Belimumab is a fully humanized IgG1γ monoclo- nal antibody directed against the soluble B lympho- cyte stimulator (BLyS) (6). It is the only approved biologic agent for the treatment of SLE. It is indi- cated as an add-on therapy for the treatment of adult patients with active, autoantibody-positive SLE, who have previously received standard therapy. Be- limumab is generally well-tolerated, with common adverse effects including infections, infusion reac- tions, hypersensitivity, headache, nausea, and fa- tigue. We present the case of a 50-year-old woman with SLE who experienced a severe cutaneous adverse reaction two months after initiating treatment with belimumab. Ref: Ro J Rheumatol. 2019;28(3) DOI: 10.37897/RJR.2019.3.5 Article History: Received: 16 August 2019 Accepted: 30 August 2019