Pertussis-Associated Leukocytosis Management Overview: Case Series

Background Pertussis, or whooping cough, is a highly contagious respiratory infection produced by Bordetella pertussis. Pertussis in infants may produce serious sequelae, such as hyperleukocytosis, an extreme elevation in white blood cell number, for which elevated morbidity and mortality are reported. Pertussis toxin is thought to be primarily responsible for the pathophysiology of pertussis-related leukocytosis, but it is not well understood. Objective The aim of this study is to define the clinical presentation, laboratory findings, therapeutic options, and course of six children with confirmed or suspected pertussis, with a focus on correlation with leukemoid reactions and the investigation of exchange transfusion treatment. Methods We retrospectively reviewed six cases of infant pertussis infection confirmed by PCR with leukocytosis necessitating admission to the Pediatric Intensive Care Unit between June 2024 and February 2025. Treatment included supportive therapy, hyperhydration, simple blood transfusion, and/or exchange transfusion. Results All six patients presented with varying levels of leukocytosis consistent with leukemoid reaction, with WBC counts ranging from 33.9 to 127 × 10 9 /L. Progressive normalization of the WBC counts was seen with interventions such as blood transfusion, hyperhydration, and exchange transfusion. Five patients were discharged in a stable state without major complications, and despite intensive management, one preterm infant died. Conclusion Pertussis in early infancy, especially in preterm or poorly vaccinated neonates, can progress rapidly, frequently leading to severe leukocytosis and cardiopulmonary compromise. Leukemoid reaction can be a marker of disease severity and poor outcome. Prompt recognition of the disease, immediate respiratory support, and proper consideration for exchange transfusion are key to improving survival. The series highlights the urgent need for prevention of pertussis through maternal vaccination and vaccination of infants early in life.