[Plasmacytosis and dengue fever: an underestimated abnormality?]

A significant peripheral blood plasmacytosis is a rare finding associated with viral infections. We reported five consecutive cases of dengue virus infection, with circulating plasma cells.

Three women and two men, aged 26 to 75 years, had returned from French West Indies less than one week before the onset of the symptoms (mean: 2.5 days). The transient blood plasmacytosis was variable in intensity (0.1 to 0.8 G/L) with a maximal level between the fourth and the seventh day following the onset of the symptoms, and was associated in four patients, with activated lymphocytes and lympho-plasma cells.

Reactive plasmacytosis during dengue fever is common and probably underestimated because it is transient and only identified by careful microscopic examination of a blood smear. Plasmacytosis could be explained by the intensity of the immunological response and the production of large amount of interleukins.