Abstract: A young male patient was diagnosed with aplastic anemia accompanied by paroxysmal nocturnal hemoglobinuria (PNH), and achieved only partial remission after immunosuppressive therapy. Over the past year, his anemia worsened, leading to transfusion dependence, which was considered to be caused by active hemolysis of PNH. Despite switching to eculizumab treatment, his anemia continued to deteriorate. A detailed medical history revealed chronic periodontal infection, with periodontal pain, purulent discharge, and fever in the past month. Multidisciplinary discussion suggested that chronic odontogenic infection activating the complement system was the primary cause of aggravated PNH hemolysis, and the acute infection affected the efficacy of eculizumab. Based on multidisciplinary consultation, a treatment plan was formulated, including intravenous antibiotics combined with periodontal irrigation and tooth extraction to control odontogenic infection, while continuing regular eculizumab infusion. The patient′s symptoms improved, hemoglobin levels rose rapidly, and he was no longer transfusion-dependent. This case provides an empirical reference for addressing difficulties encountered in the treatment of rare diseases with new drugs through multidisciplinary collaborative diagnosis and treatment.