Picture Prognosis

A 60-year-old male with acute epigastric pain underwent imaging revealing diffuse abdominal and pelvic lymphadenopathy. Biopsy confirmed grade 1-2 follicular lymphoma. He developed B symptoms three months later and started bendamustine/rituximab. Post-chemotherapy, he presented with fever, diarrhea, anemia, and thrombocytopenia. What complication has likely occurred?