Aggregation of neutrophils in peripheral blood smears is a very rare, mostly self-limiting phenomenon and may result in pseudo leukopenia. The exact reason for neutrophil aggregation in vitro has not been clarified, its relation to the use of ethylene diamine tetra acetate acid as an anticoagulant has been described in adults A 3-year-old boy was referred to Valli e Asr hospital Arak, Iran. The EDTA blood sample was first loaded with the Impedance-based KX-11 Sysmex, which showed a decrease in neutrophils and was observed in the peripheral blood of the Neutrophil aggregation. The blood sample was re-read with the XN-L-350 Sysmex, which is based on the optic method, which showed the number of neutrophils in Norman. Although neutrophil aggregation is extremely rare in daily haematological practice, physicians should be aware of this phenomenon as it may be the cause of leukocytopenia. Therefore, manual differentials should be performed in cases flagged for low leukocyte or neutrophil counts.
