Acute Appendicitis at Stem Cell Infusion During Autologous Transplantation for HIV-Associated Diffuse Large B-cell Lymphoma: A Case Report

Acute appendicitis is an exceptionally rare complication of autologous hematopoietic stem cell transplantation (HSCT) and represents a diagnostic challenge, since its presentation overlaps with conditioning-related gastrointestinal toxicity and neutropenic enterocolitis. Published data are limited to isolated case reports, and its occurrence during autologous stem cell transplantation (ASCT) for human immunodeficiency virus (HIV)-associated lymphoma has not previously been described. We report the case of a 39-year-old man with HIV-associated diffuse large B-cell lymphoma (DLBCL), non-germinal center subtype, Ann Arbor stage IV with gastric involvement, and a high-risk age-adjusted International Prognostic Index (score three). After failure of first-line rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) with a Deauville score of four on interim positron emission tomography-computed tomography, complete metabolic remission was achieved with two cycles of second-line rituximab, dexamethasone, cytarabine, and carboplatin (R-DHAC). The patient then proceeded to carmustine, etoposide, cytarabine, and melphalan (BEAM)-conditioned ASCT under controlled HIV viral load and persistent CD4 lymphopenia. On the day of stem cell infusion (day zero), he developed right lower quadrant tenderness associated with elevated inflammatory markers; abdominopelvic computed tomography demonstrated acute appendicitis. Emergency laparoscopic appendectomy revealed ulcerative appendicitis without tumor infiltration on histopathology. The postoperative course during aplasia was complicated by septic shock due to multidrug-resistant Pseudomonas aeruginosa bacteremia, with a favorable evolution to broad-spectrum antibiotic therapy and vasopressor support. Neutrophil engraftment occurred on day +14, and the patient was discharged on day +20, with no further complications and a complete remission maintained at six months of follow-up. This case illustrates that acute appendicitis may occur as early as the day of stem cell infusion. Its presentation may be initially indistinguishable from melphalan-induced gastrointestinal toxicity, which makes early abdominopelvic CT indispensable for an early diagnosis. It also shows that, even when surgical source control is timely, profound aplasia and the HIV-related CD4 lymphopenia predispose to severe infectious complications. This justifies anticipatory broad-spectrum coverage adapted to local multidrug-resistant epidemiology and close multidisciplinary monitoring throughout the aplastic phase.