Among acute lymphoblastic leukemia (ALL), 40% of affected patients are diagnosed after the age of 20. Compared to pediatricians, adult hemato-oncologists are less familiar with complex pediatric ALL regimens and have perceived that pediatric ALL regimens are too toxic in the adult population. Meanwhile, multiple retrospective analyzes showed the superiority of pediatric regimens among the older adults and young adolescents (AYAs) group over adult regimens. A series of prospective studies have made it apparent that pediatric-inspired ALL regimens are feasible in AYAs, with manageable toxicities and potentially more encouraging results. However, the complications in the adult population are still to be explored. Although cytomegalovirus (CMV) viremia and infections are increasingly recognized in pediatric ALL cases, we generally do not experience it frequently in adult cases with conventional strategies. Herein we represent a 38-year-old man diagnosed with ALL and treated with pediatric inspired GRAALL-2003 protocol. Following a successful induction phase, he had pancytopenia, deep lymphopenia, fever and diarrhea in the 9th month of maintenance therapy. With increased serum ferritin and triglyceride levels, he had features of macrophage activation syndrome. The bone marrow biopsy did not reveal any relapse or hemophagocytosis. We detected highly increased levels of CMV DNA (657.262 copies/mL) in blood analysis.