Differentiating Juvenile Myelomonocytic Leukemia From Infectious Disease

To The Editor:Two recent articles in BLOOD 1,2 review the findings and outcome of juvenile myelomonocytic leukemia (JMML).Both omit an important aspect of JMLL: its differentiation from infectious disease.Several disseminated microbial infections of infancy can result in persistent fever, failure to thrive, hepatosplenomegaly, skin lesions, anemia, thrombocytopenia, and myelomonocytosis, including Epstein-Barr virus (EBV), cytomegalovirus (CMV), human herpes virus-6 (HHV-6), histoplasma, mycobacteria, and toxoplasma.Thorough investigation for infection is needed in infants with these findings to avoid erroneous diagnosis and mistaken interventions.Herrod et al 3 reported two infants with persistent EBV infection and findings consistent with JMML, including increased numbers of F and i cells and abnormal granulocyte-macrophage colony formation in vitro.Both recovered without treatment and remained well.This raises the possibility that some of the long-term survivors reported by Niemeyer et al and Arico et al had similar infections rather than leukemia.Neonatal CMV and HHV-6 infections can also mimic JMML.4,5 Might erroneous diagnosis account for the better prognosis reported for patients with JMML who are less than 6 months old? 2 The excellent reviews of Niemeyer et al and Arico et al suggest that JMML represents a group of diseases rather than a single entity.Careful investigation for microbial associations, including more recently identi-fied herpesviruses, might contribute to understanding pathogenesis as well as to diagnosis and management.