Famotidine-induced reactive plasmacytosis and generalized lymphadenopathy: a case report and review of the literature

We report the case of a 53-year-old woman who presented with plasmacytosis, hypergammaglobulinemia, and multiple lymphadenopathy after upper respiratory infection. Although these symptoms mimicked those of plasma cell leukemia, serum immunoelectrophoresis, flow cytometry, and immunohistochemistry of bone marrow and an enlarged lymph node revealed polyclonal proliferation of plasma cells. In the absence of treatment, the plasmacytosis improved soon after ceasing the previously prescribed medications. A drug reaction was suspected as the cause of plasmacytosis because the patient had high serum IgE levels that decreased after discontinuation of the medications. A drug-induced lymphocyte stimulation test was performed for all of the drugs prescribed before admission: a positive result was only obtained for famotidine. The present case represents the first report of marked famotidine-associated plasmacytosis.