[Malignant pertussis in the young infant]. / La coqueluche maligne du petit nourrisson.

UNLABELLED: Pertussis remains in France the first cause of bacterial, infectious death in infant aged 10 days to 2 months. It is especially in this age group that malignant pertussis occurs. CASE REPORT: A 40-day-old infant was admitted in the intensive care unit with symptoms of bronchiolitis along with a 200 bpm permanent tachycardia. He presented a marked leukocytosis with lymphocytosis. On the second day, convulsions and coma occurred, followed rapidly by respiratory failure, with a subsequent deterioration due to the development of severe pulmonary hypertension. Circulatory failure caused the infant's death on the beginning of the 5th day. Pertussis was confirmed by PCR on nasopharyngeal swab. Intra-familial contamination was most likely. COMMENTS: Malignant pertussis is characterized by the very young age of patients, permanent tachycardia sine materia, dyspnea with early respiratory failure, frequent neurological symptoms, severe hyperleukocytosis and hyperlymphocytosis, and deep hyponatremia with oliguria and edema. Mortality remains superior to 75% despite the various treatments and life support measures that have been attempted. Adult pertussis, which represents one third of the cases of prolonged cough in this age group, is the main source of contamination of non-immunized young infants. This mode of transmission stresses the importance of the generalization of pertussis vaccine booster in early adolescence, which is recommended in France since 1998. Its extension towards the adult age is under study.