Sézary syndrome with elevated serum IgE and hypereosinophilia: role of dysregulated cytokine production.

A 62-year-old man presented with a 4-year history of a pruritic erythematous rash. Initial workup was not diagnostic, and the rash was refractory to standard treatment. A complete blood cell count demonstrated a white cell count of 9100 cells/microliter with 61% polymorphonuclear neutrophils, 16% eosinophils, and 17% lymphocytes. A serum protein electrophoresis revealed an M spike identified as IgG kappa. His IgE level was 11,900 IU/ml. A bone marrow biopsy specimen demonstrated "atypical plasma cells" but was not diagnostic for myeloma. Peripheral blood smear was remarkable for highly convoluted lymphoid cells diagnostic for Sézary T cells. Consistent with this diagnosis, 89% of his peripheral blood CD2+ cells expressed CD4. The eosinophilia, elevated IgE level, and monoclonal gammopathy led to further investigations. Circulating adherent monocytes were 96% positive for presumed low-affinity IgE receptor expression as shown by surface IgE binding. In a 9-day lymphocyte coculture, the patient's T lymphocytes induced IgE production in vitro (1.25 ng/ml) by a normal donor's cultured B cells. A healthy donor's T cells failed to induce IgE production (0 ng/ml) in a similar culture system. In situ hybridization with an Sulfur-35-labeled cDNA probe revealed interleukin-4 mRNA expression by 84% and interleukin-2 mRNA expression by 62% of nonadherent peripheral blood mononuclear cells. Interleukin-5 mRNA was shown by reverse transcription and the polymerase chain reaction. These studies demonstrate a subject with Sézary T cell leukemia with hypereosinophilia and elevated IgE due to presumed enhanced interleukin-4 and interleukin-5 production by the Sézary T cells.