Early-Onset Neutropenia Induced by Rituximab in a Patient With Pemphigus Vulgaris: A Case Report and Literature Review.

Rituximab (RTX), a chimeric anti-CD20 monoclonal antibody, is increasingly used in autoimmune diseases. Although generally safe, it may rarely induce cytopenias, particularly early-onset neutropenia (EON) or late-onset neutropenia (LON), with LON being more frequent. We report the case of a 48-year-old female patient with pemphigus vulgaris who developed EON 21 days after RTX initiation. After the second RTX infusion, she presented with severe neutropenia, anemia, fever, respiratory symptoms, and Staphylococcus aureus sepsis. Despite antibiotics and intensive care, she died of refractory septic shock. EON occurs within four weeks of RTX administration and remains less commonly reported than LON. Only 13 cases have been described in the literature, but none was fatal. This is the first reported fatal case of EON in pemphigus vulgaris and the second reported fatal case in a dermatologic disease. This case highlights the need for awareness of EON as a rare but potentially life-threatening RTX complication. Close blood count monitoring during and after RTX therapy may allow earlier detection and intervention.