Myasthenic syndrome and oligoclonal lymphocytosis: Evolution into chronic lymphocytic leukemia

We report a patient with myasthenic syndrome who, 2 years after diagnosis, developed an oligoclonal lymphocytosis. This disorder was sustained by both κ+ and λ+ CD5+ B-cell clones; over the following year, the white blood cell count increased and phenotypic characterization revealed a clear imbalance in the immunoglobulin light chain ratio (84% κ+). Accordingly, persistence of a κ+ B-cell clone was disclosed by molecular analysis of immunoglobulin heavy chain gene rearrangements. Our results may suggest that prolonged immune system stimulation due to an autoimmune disease can drive a benign lymphoproliferation into a B-cell neoplastic process.