Persistent polyclonal lymphocytosis with binucleated B lymphocytes: a genetic predisposition

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Abstract
Summary. Persistent lymphocytosis is usually associated with a malignant lymphoproliferative disease (MLPD). We report six female patients presenting a chronic, moderate lymphocytosis of 2–16 years duration with atypical binucleated lymphocytes on peripheral blood smears. Further investigation showed a polyclonal increase in serum IgM and HLA‐DR7 phenotype in all patients. The B cells were polyclonal because Southern hybridization of DNA and polymerase chain reaction failed to demonstrate a clonal rearrangement of immunoglobulin heavy chain genes. Peripheral blood examination showed binucleated lymphocytes in a family member of two of the cases; taken together with the association with HLA‐DR7 these data suggest a genetic predisposition. The identification of this benign syndrome is important in order to prevent its misdiagnosis as a MLPD.