Abstract
BACKGROUND: Cytomegalovirus (CMV), an opportunistic pathogen, can cause severe pneumonia in Chronic myeloid leukemia (CML) children undergoing hematopoietic stem cell transplantation (HSCT), resulting in a high mortality rate. CASE PRESENTATION: An 11-year-old girl was hospitalized with a 3-day history of fever and vomiting, presenting with anemia and massive splenomegaly. A series of diagnostic tests, including blood cell count, bone marrow analysis, flow cytometry, chromosomal examination, and genetic testing, confirmed a diagnosis of CML at blast-phase. Following a one-year course of tyrosine kinase inhibitor-based chemotherapy, the patient entered the chronic phase and underwent a 6/12 human leukocyte antigen (HLA)-matched HSCT from her father. Two weeks after HSCT, the patient developed grade III skin graft-versus-host disease and hemorrhagic cystitis, which were effectively treated and symptoms were alleviated. One month after transplantation, the patient presented with serious pneumonia and pancytopenia. Although five blood cultures and two sputum cultures were all negative, metagenomic next-generation sequencing (mNGS) of bronchoalveolar lavage fluid (BALF) indicated a high abundance of CMV (16635 reads), leading to a diagnosis of CMV pneumonia. Notably, no typical resistant mutations were identified in the CMV genome. Targeted treatment with sodium phosphonoformate and letermovir was administered. As a result, the patient's condition improved remarkably with the abundance of CMV decreasing to only 12 reads. After one-year of monitoring, the primary disease was well-controlled, and no CMV reactivation was observed. CONCLUSION: The diagnosis, treatment, and monitoring of pneumonia is crucial in post-HSCT patients. This case highlights the utility of mNGS in diagnosing and monitoring CMV pneumonia in post - HSCT patient and the effectiveness of targeted therapy in managing such infections.