Background
Monoclonal antibodies have been used for the modulation of immune responses in several disorders, including cancer, autoimmune, and infectious diseases. 1
Rituximab (RTX) is a chimeric monoclonal antibody that specifically binds to the B-cell surface antigen CD20 which produces antibody-dependent cell- and complement-mediated cytotoxicity in these cells. 2-4 The mechanism of action of RTX including, regulating cell-cycle signaling, inducing apoptosis, improving cells’ sensitization to cytotoxic drugs, complement-mediated cytotoxicity, and antibody-dependent cellular cytotoxicity 4
RTX has been used in the treatment of previously untreated or previously treated CD20-positive chronic lymphocytic leukemia (CLL) in adults5, granulomatosis with polyangiitis6, microscopic polyangiitis 7, non-Hodgkin lymphomas 8, pemphigus vulgaris9, rheumatoid arthritis 10, and other off-label uses such as acquired thrombotic thrombocytopenic purpura 11, Waldenström macroglobulinemia12, refractory autoimmune hemolytic anemia13, etc.
As a single agent, RTX (1000 mg) is usually administered weekly for 4 weeks. When used in combination with chemotherapy, it is often administered every 3 to 4 weeks. The pharmacokinetics of RTX is like that seen with human immunoglobulin G (IgG). 14
Pemphigus is an autoimmune disease characterized by blisters and erosions of the skin and mucosal membranes. It is mediated by autoantibodies that target the transmembranous adhesion glycoproteins desmoglein 1 (Dsg1) and desmoglein 3 (Dsg3). Pemphigus Vulgaris (PV) is the major subtype of Pemphigus and is characterized as having a progressive course that leads to death if the disease is not treated.15
Several previous studies have reported adverse events such as cough, dyspnea, fever, and erythema, as well as late adverse events such as severe infection and agranulocytosis in patients treated with RTX.16
Serum sickness is a rare hypersensitivity reaction due to foreign antigens, causing fever, rash, and arthralgia. 17 RTX may produce human anti-chimeric antibodies (HACAs) and induce serum sickness. 18 Although serum sickness is relatively common among autoimmune disease patients, there are few reports in patients with PV.