Gut Microbiome as a Predictive Biomarker for Febrile Neutropenia in Pediatric Acute Lymphoblastic Leukemia: A Clinical Integrative Framework

Introduction Febrile neutropenia (FN) is a common and potentially life-threatening complication mostly observed in pediatric patients undergoing chemotherapeutic regimen for the treatment of hematological malignancies, such as acute lymphoblastic leukemia (ALL).[ 1 ] It is characterized by a single oral temperature ≥ 38.3°C (101.0°F) or an oral temperature ≥ 38.0°C (100.4°F) sustained for over an hour or occurring twice within a 24-hour period. An absolute neutrophil count (ANC) < 0.5 × 10 9 /L or ANC < 1.0 × 10 9 /L is expected to decrease to < 0.5 × 10 9 /L over the subsequent 48 hours, accompanied by fever.[ 2 ] [ 3 ] Despite standardized chemotherapy protocols, FN risk in the pediatric population remains heterogeneous, with current risk stratification relying on postonset clinical features, limiting early intervention.[ 4 ] [ 5 ] [ 6 ] Recent reports link baseline gut microbial dysbiosis, marked by reduced microbial diversity and elevated Proteobacteria, to FN complications, suggesting their prospective role as an anticipatory biomarker, providing a valuable window for early risk stratification and targeted supportive care.[ 7 ] [ 8 ] [ 9 ] [ 10 ] [ 11 ] [ 12 ] [ 13 ] [ 14 ] Authors' Contributions B.C. and R.D. collaboratively prepared and submitted the manuscript. B.C. has drafted the manuscript, and R.D. has proofread the manuscript and extensively helped by providing essential information. Patient's Consent This is a Perspective article so patient consent is not required. No real patient, patient data or identifiable clinical information is involved. The illustrative case described is purely hypothetical and used for conceptual explanation only. Publication History Article published online: 06 January 2026 © 2026. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. (https://creativecommons.org/licenses/by/4.0/) Thieme Medical and Scientific Publishers Pvt. Ltd. A-12, 2nd Floor, Sector 2, Noida-201301 UP, India