Is leukocytosis a predictor of mortality in severe pertussis infection?

Bordetella pertussis causing severe respiratory failure in infants that is unresponsive to treatment is well described. Pulmonary hypertension is a prominent feature of such cases. In this series of 13 critically ill infants with B. pertussis, hyperleukocytosis ( > 100 x 10(9)/l) was an independent predictor of death. We suggest that such extreme leukocytosis may contribute to disease severity via the formation of aggregates in the pulmonary vasculature.