[Chronic granular T lymphocytosis of undetermined significance]

The clinical, morphologic, immunologic, functional, serologic and cytogenetic features of 4 cases of chronic granular T cell lymphocytosis with neutropenia were studied. The records of these patients were reviewed and an infectious event preceding the development of the disorder could be documented in 3 cases, suggesting a cause and effect relationship. A benign monoclonal gammopathy was detected in the remaining patient. The clinical picture was characterized by moderate blood and bone marrow lymphocytosis, neutropenia, hepatosplenomegaly, absence of lymphadenopathy, and a stable course, observed over a period of up to 11 years. Surface marker analysis in all the patients showed the common membrane phenotype of granular T cell lymphocytosis (CD3+, CD4-, CD8+, Leu7+). One patient treated with steroid therapy had reversal of lymphocytosis and severe neutropenia, which both recurred after steroids were withdrawn. The disorder again resolved after pulse steroid treatment. From these findings and a review of the literature, we suggest that granular T cell lymphocytosis with the immunologic phenotype exemplified by our cases is a distinct reactive or immunoregulatory disorder. In view of the similarities in character to benign monoclonal B cell lymphocytosis and idiopathic paraproteinaemia, we suggest that this disorder be termed chronic granular T cell lymphocytosis of undetermined significance.