[Malignant pertussis: an underdiagnosed illness].

PURPOSE: Malignant pertussis is a rare life-threatening illness characterized by severe respiratory failure, severe leukocytosis, and pulmonary hypertension. The purpose of this study was to determine the prevalence of malignant pertussis in infants admitted to a pediatric intensive care unit (PICU) for severe acute respiratory failure associated with severe leukocytosis. METHODS: This retrospective study was based on review of the medical charts of infants aged less than 3 months admitted to the PICU between 2006 and 2008 for severe acute respiratory failure requiring mechanical ventilation with leukocytosis greater than 50,000/mm3. Clinical and laboratory data were collected. Polymerase chain reaction (PCR) for detection of Bordetella pertussis was performed on nasopharyngeal washes (NPW) stored at -70 degrees C. RESULTS: Ten patients meeting inclusion criteria were identified. Median age was 2.1 months (range, 0.6 - 3). None of the infants had been vaccinated against pertussis. Although PCR for pertussis was positive in all ten cases, presumptive diagnosis was made in only 3 patients during hospitalization. Nine patients died within a mean of 4.7 +/- 3.3 days after admission. The cause of death was refractory shock and hypoxemia in all cases. Only one patient survived. CONCLUSION: Malignant pertussis is a severe disease that is almost always fatal. It was underdiagnosed in our PICU. Use of PCR for detection of B. pertussis, i.e., the reference method, should be promoted in developing countries.