Low-dose methotrexate in PAH related to T-cell large granular lymphocyte leukaemia.

T-cell large granular lymphocytes (LGLs) are a morphologically distinct subset of normal peripheral blood mononuclear cells classified into two major lineages based on the presence of the CD3 receptor: CD3+ lymphocytes and CD3natural killer cells. The revised European-American classification of lymphoid neoplasms [2] considers clonal proliferation of these cells, or LGL leukaemia (as proved by a cytogenetic study of the rearrangement of the Tcell receptor), as a distinct type of peripheral T-cell neoplasm. In the vast majority of cases, LGL leukaemia has a CD3+, ab+, CD4-, CD8+, CD16+, CD57+ and CD56phenotype and an indolent course [3]. Overexpression of some natural killer receptors (NKRs) of the killer immunoglobulin-like receptor family, such as CD94 and CD158b, is sometimes observed [4–6]. T-cell LGL leukaemia is frequently associated with various autoimmune diseases, particularly rheumatoid arthritis (30% of cases) and haematological disorders (e.g. neutropenia) [3].