Aggregation of neutrophils in peripheral blood smears is a very rare, mostly self-limiting phenomenon and may result in pseudoleukopenia. In the majority of cases, malignancies, infections, or hepatic disorders have been identified as the underlying condition. Although the exact reason for neutrophil aggregation in vitro has not been clarified, its relation to the use of ethylenediaminetetraacetate acid as an anticoagulant has been described in adults. We report here on the occurrence of transient neutrophil aggregation in a 13-year-old girl with Herpes simplex and concomitant Mycoplasma pneumoniae infection.
