C50-02 Fatal Disseminated Cytomegalovirus Causing Refractory Shock and ARDS After Rituximab and High-Dose Steroid Therapy: A Call for Vigilance in Non-Transplant Immunosuppression

Introduction Rituximab is an immunoglobulin G1 monoclonal antibody that promotes B-cell depletion which leads to hypogammaglobulinemia, impaired viral neutralization, and diminished antigen presentation to CD8+ cytotoxic T lymphocytes. Simultaneously, corticosteroids suppress IL-2 production, inhibit NF-κB-mediated transcription, and induce T-cell apoptosis, collectively silencing both humoral and cellular antiviral defenses. The molecular mechanisms by which CMV establishes and maintains latency and reactivates remains poorly understood. We present a case of CMV colitis with subsequent multiorgan involvement in a patient treated with rituximab and corticosteroids for autoimmune encephalitis, illustrating the severe spectrum of CMV disease in the intensive care setting Case presentation 43 yo male with no prior PMH, who was diagnosed in May 2025 with autoimmune encephalitis, treated with steroids, IVIG and one dose of rituximab on 6/12/2025 with initial improvement in symptoms. Patient returned to hospital on 6/16 with AMS, tachycardia and diarrhea, Initial imaging showed concerns for enteritis. Further workup including colonoscopy biopsy revealed CMV colitis, blood work with positive CMV DNR PCR, for which patient was treated with Valganciclovir. Hospital course was complicated with refractory shock requiring multiple pressors, worsening mental status requiring intubation, and high anion gap metabolic acidosis with concomitant respiratory acidosis. Patient received immunoglobulin infusions, pRBC and platelets due to pancytopenia and hypogammaglobulinemia. Within admission developed bilateral lung infiltrates with increasing Peep and FiO2 requirements, meeting criteria for moderate ARDS. Ultimately suffer from cardiac arrest, resuscitative measures were unsuccessful, and patient expired Discussion The intersection between immunotherapies and viral reactivation represents a challenge in critical care. A prior multicenter, retrospective study in CMV-end organ dysfunction in 18 ICUs Europe found that hospital mortality was 61.4% overall. Early recognition is diagnostically challenging given that standard bacterial cultures are often negative, and CMV PCR or tissue biopsy confirmation may come too late. Although antiviral therapy remains the cornerstone of treatment, outcomes depend on the degree of immune reconstitution. There have been cases reported in NEJM describing fatal CMV reactivation after single-dose rituximab, suggesting that even limited exposure may be enough to unmask latent infection in susceptible individuals. This case provides the awareness that rituximab-associated CMV disease is not restricted to hematologic malignancy or transplant populations This abstract is funded by: None