At autopsy, JAK2 V617F recipients had significant splenomegaly, particularly in Balb/c mice (mean spleen weight 0.58±0.19 g versus 0.08±0.01 for Balb/c recipients of JAK2 WT-transduced BM, P = 0.0023 by unpaired t-test), but no involvement of lymph nodes or thymus, and no pulmonary hemorrhages. This evidence concerns the gene JAK2 and Splenomegaly.