(834) Malignant Pertussis in an Unimmunized Toddler Requiring Exchange Transfusion

Introduction: Bordetella pertussis is a bacterium that typically causes respiratory infections in infants under 3 months of age. Malignant pertussis (MP) is characterized by severe leukocytosis, pulmonary hypertension, and respiratory failure requiring mechanical ventilation. Significant leukocytosis has been associated with increased mortality in MP, often requiring exchange transfusion for leukoreduction.

Description: A 13-month-old unimmunized girl was admitted to the pediatric intensive care unit (PICU) for acute hypoxic respiratory failure secondary to Bordetella pertussis infection. Initial white blood cell count (WBC) was 79,150/μL. On PICU day 1, her respiratory status declined, requiring endotracheal intubation and mechanical ventilation. She progressed to severe acute respiratory distress syndrome with refractory hypoxemia, shock, and vascular access line occlusion secondary to thrombosis. The possibility of hyperviscosity syndrome was considered in the setting of significant hyperleukocytosis. She was started on inhaled nitric oxide (iNO) and epoprostenol. Given multiorgan dysfunction and suboptimal response to clinical management, whole blood double volume exchange transfusion was performed for leukoreduction. Post-procedure, oxygenation improved significantly. WBC goal of < 35,000/μL was achieved about 24 hours post-exchange transfusion. Further complications included disseminated intravascular coagulation (DIC) resulting in cerebral infarcts. As of submission, the patient remains intubated but clinically improving with discontinuation of iNO and epoprostenol and resolution of DIC.

Discussion: Malignant pertussis infections typically occur in infants < 3 months of age. Pertussis toxin has been demonstrated to cause severe leukocytosis. WBC counts > 30,000/ μL causing pulmonary hypertension, resulting in MP infections, have been associated with increased mortality as high as 70%. Current literature has described cases of critical/malignant pertussis requiring exchange transfusion in infants, but few cases have described this disease process and treatment in older children. As immunization rates decline across the United States, pertussis should be suspected in any unimmunized child with persistent paroxysmal cough and unexplained leukocytosis.