Introduction Sepsis is one of the most common causes of mortality and morbidity in the Pediatric Intensive Care Unit (PICU). Clinical as well as laboratory parameters in sepsis are not specific and the outcome of sepsis might be devastating if misdiagnosed.

The aim of this observational study is to analyze the time course of eosinophilia during the stay in PICU in documented infected children with sepsis compared with post surgery children without infection.

Methods 11 children admitted with documented infection and severe sepsis (sepsis group (SG)) compared with 11 age matched children admitted to the PICU after a surgical procedure without documented infection (control group (CG)).

The timely course of the white blood cell count (WBC), C-reactive protein and the absolute value of the circulating eosinophil leukocytes were followed.

Results The mean age in the SG was 4.1 years compared with 3.9 years in the CG. The cause of the sepsis in the SG was severe pneumonia (5 patients), meningitis (4 patients), Peritonitis (1patient) and mastoiditis (1 patient). In the CG, the cause of admission into PICU was major neurosurgery (5 patients), abdominal surgery (3 patients), urosurgery (2 patients) and cardiosurgery (1 patient). Eosinopenia was correlated with very high CRP and very severe sepsis.

Conclusions Eosinopenia seems to be an early, rapid, available, inexpensive biological marker and correlates with the severity and the prognosis of the illness in severely infected children. Further prospective data are needed to validate this preliminary result.