A case of granular lymphocyte proliferation with T-cell phenotype

Immunological studies were conducted on a case of granular lymphocytosis with benign clinical feature. A 60-year-old Japanese woman was found incidentally to have lymphocytosis when she had a common cold. A complete blood count showed 47,200 leukocyte per mm3 with 82% granular lymphocytes, 8% small lymphocytes and others. Hemoglobin was 11.5 g/dl and platelet count was 365 X 10(3)/mm3. Surface marker study revealed erythrocyte-rosettes 94%, Leu-1 59%, Leu-2a 70%, Leu-3a 14%, Leu-4 98%, Leu-7 57%, Leu-11 5%, HLA-DR 92%, BA-2 6%, common ALL antigen 4%, and surface immunoglobulin 2%. These results suggest granular lymphocyte proliferation with T-cell phenotype. Natural killer activity was 4.5%, but it was elevated to 11.4% after interleukin-2 stimulation by 2 days' culture. Human T-cell lymphotropic virus-I antibody was absent. No lymphadenopathy and no hepatosplenomegaly were seen, except for bone marrow infiltration of granular lymphocytes. The patient has been in good health without any acute distress. The leukocyte count has gradually decreased to 12,300/mm3 with 79% lymphocytes in 6 months of follow-up without any therapy. This case is suggestive of benign lymphocytosis, although similar cases have been reported previously as chronic lymphocytic leukemia with T-cell marker and/or natural killer function.