#00061936

A 64-year-old man with a recent diagnosis of autoimmune hemolytic anemia presented with fevers. Laboratory tests showed white blood cell count of 19,000 x 109/L (65% lymphocytes), anemia, thrombocytopenia, and lactate dehydrogenase of 702. Blood film examination demonstrated large granular lymphocytes (A- black arrow) and circulating blasts of medium size, with variable nucleoli and no Auer rods (A- green arrow). Bone marrow was hypercellular, with 30% blasts, erythroid hyperplasia with megaloblastoid and dysplastic changes in up to 20% of cells, and atypical lymphocytes with cytoplasmic granules (B). Immunophenotype showed two different abnormal populations: the blast population (HLA-DR+/CD7+/CD4+/CD117+) consistent with acute myeloid leukemia (AML) and a TCR V-beta chain-restricted population of CD3+/CD8+/CD56+/CD57+/CD26- T cells, compatible with large granular lymphocytic (LGL) leukemia. Molecular studies showed mutations in DNMT3A and TP53 but no mutations in STAT3 and STAT5A/5B. The patient was treated with decitabine for TP53-mutated AML and steroids for LGL leukemia.

LGL leukemia is a clonal population of post-thymic activated T cells, likely arising from chronic antigenic stimulation. It often presents with cytopenias and autoimmune phenomena; mutations in STAT3 and STAT5A/B have been reported. Low level LGL proliferation is not uncommon in myelodysplastic syndrome, but is rarely reported in AML.