3, 4, 5, 6, 7 There is a frequent association with a wide variety of autoimmune diseases (33%) and other malignancies (13%).8 Its diagnosis is based on a persistent (>6 months) morphologically and/or immunophenotypically increased clonal CD3+/CD57+ LGL population in PB, usually >2 × 109/l, though a lower count (range 0.4–2 × 109/l) may also be compatible with a diagnosis of T-LGL leukemia.9, 10 T-LGL leukemias can be divided into three groups on the basis of their immunophenotypical and molecular characteristics: CD8+, CD4+ and T-cell receptor (TCR)γδ+ T-LGL. This evidence concerns the gene CD4 and autoimmune disease.