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.
We suggest that such extreme leukocytosis may contribute to disease severity via the formation of aggregates in the pulmonary vasculature. In two patients lymphocyte subset analysis was also performed. Histories were typical, with paroxysms of coughing and cyanotic episodes, admissions occurried predominantly during reported epidemic peaks. A detailed analysis of the circulating lymphocytes was performed in two patients. These four deaths raise the possibility of a different pathophysiology in cases of extreme leukocytosis.