Life-threatening refractory leukopenia in a patient with systemic lupus erythematosus successfully treated with rituximab.

Leukopenia can occur because of lymphopenia, neutropenia or both. Leukopenia appearing as a common hematological manifestation of systemic lupus erythematosus (SLE) is typically mild, but potentially life-threatening. However, no consensus has been reached on treatment strategies for severe leukopenia in SLE. An 18-year-old man was diagnosed with SLE based on fever, malar and discoid rash, leukopenia, hypocomplementemia, and a positive result for anti-nuclear antibodies. Despite administration of high-dose glucocorticoids combined with immunosuppressants (including intravenous cyclophosphamide, mycophenolate mofetil, tacrolimus, and azathioprine) and intravenous immunoglobulin G (IgG) treatment, leukocyte count declined to 50/μL, accompanied by positive anti-neutrophil IgG antibodies. Bone marrow biopsy revealed normocellular marrow without hemophagocytosis. The patient developed febrile dyspnea due to pulmonary infection. Administration of rituximab (375 mg/m² weekly for 4 weeks) led to rapid, sustained recovery of leukocyte count. The patient then recovered from respiratory failure with anti-microbial therapy. Prednisolone was successfully tapered to 5 mg/day. This case suggests that rituximab may provide an effective therapeutic option for severe treatment-refractory leukopenia in SLE.