A 2-year-old boy with VACTERL association with multiple congenital anomalies was hospitalized with fever without a source. He was 4 months status post–deceased donor renal transplant for solitary dysplastic kidney. Immunosuppression included tacrolimus and azathioprine. History was otherwise notable for chronic Epstein-Barr viremia without evidence of posttransplant lymphoproliferative disorder. Complete blood count revealed a white blood cell count of 1.8 × 10⁹/L, a hemoglobin level of 7.0 g/dL, and a platelet count of 402 × 10⁹/L, with an absolute neutrophil count of 0.7 × 10⁹/L. Review of the peripheral blood film showed bilobed and occasionally hypogranular neutrophils containing round basophilic inclusions consistent with micronuclei (panels A-D). These were present in 11% of neutrophils and were absent from other leukocytes. Although the morphology of these inclusions was not entirely typical of Anaplasma phagocytophilum, he received a course of doxycycline for this infection due to his residence in an area where tick-borne infections are endemic. The inclusions persisted at stable frequency after treatment.

Howell-Jolly–like bodies in granulocytes arise secondary to stressed granulopoiesis induced by immunosuppressive drugs, viral infection, or chemotherapy, and must be differentiated from other neutrophil inclusions such as those observed in intracellular bacterial infections, genetic conditions such as Chédiak-Higashi syndrome, or Döhle bodies [Arch Pathol Lab Med. 2003;127(10):1389-1390].