Are clonal T‐cell large granular lymphocytes to blame for unexplained haematological abnormalities?

Summary Abnormalities diagnosed on routine blood work, such as mild neutropenia, anaemia, thrombocytopenia and relative lymphocytosis, often have obscure aetiologies. A series of 30 patients were evaluated for various unexplained haematological abnormalities between 1997 and 2005, and found to have circulating monoclonal T‐cell large granular lymphocytes (T‐LGL). These patients fit the diagnosis of T‐cell clonopathy of unknown significance (TCUS), which may represent a clinical spectrum of clonal T‐LGL proliferation. Our patients were characterised by a complete absence of severe neutropenia (<0·5 × 10 9 /l), absence of recurrent neutropenic infection (0%), negative rheumatoid serology (0%) and a low incidence of constitutional symptoms (20%). This overall asymptomatic clinical presentation appeared to be different from other previously reported series of TCUS or T‐LGL leukaemia who typically had symptomatology and required treatment. Our series of 30 patients represented the benign end of the spectrum of clonal T‐LGL proliferation, and might reflect diagnosis at earlier stages of the condition relative to other reported series. TCUS may be a heterogeneous and under‐diagnosed condition. This study further broadens our understanding of the clinical and laboratory manifestations of indolent clonal T‐cell proliferation, and raises our awareness of this condition. We suggest that TCUS should be considered in the diagnostic evaluation of unexplained haematological problems.