Automated leukocyte differentials in trisomy 13

We have reported a case of a 4-month-old girl who died with trisomy 13. Nuclear projections in polymorphonuclear leukocytes are diagnostically important in this syndrome and are not identified by automated leukocyte differential counting. The presence of polymorphonuclear leukocyte nuclear projections on the blood smear was identified only after the results of karyotyping were known. Recently, the importance of physician review of blood smears in anemia has been challenged. We believe this case, however, reaffirms the importance of physician blood smear review in suspected cytogenetic disease.