A patient with paroxysmal nocturnal hemoglobinuria, T cell large granular lymphocyte clonal expansion, and monoclonal gammopathy of undetermined significance

Paroxysmal nocturnal hemoglobinuria (PNH) has been described in association separately with T cell large granular lymphocyte (LGL) clonal expansions and plasma cell dyscrasias. We describe a patient with anemia related to hemolytic PNH, with concurrent T cell LGL oligoclonal expansion and IgG lambda monoclonal gammopathy of undetermined significance. Peripheral blood flow cytometry revealed decreased expression of CD55 and CD59 on erythrocytes and decreased expression of CD55 and CD66 on neutrophils. An LGL population was present in the peripheral blood and was characterized as oligoclonal by polymerase chain reaction-based analysis of the T cell receptor gamma-chain variable region. Serum protein electrophoresis with immunofixation showed a low level IgG lambda monoclonal protein. We describe the diagnostic evaluation of this patient and provide a brief review of the reported associations among PNH, LGL clonal expansion, and monoclonal gammopathy.