Idiopathic myelofibrosis without splenomegaly.

The patient described has had idiopathic myelofibrosis for 8 years. At the time of presentation, 12% of the circulating white cells were myeloblasts. In the past two years, the white blood count has been as high as 18,000/mm3 with 50% myeloblasts. Of significance is the absence of splenomegaly over the eight year period of observation. The rarity of the absence of significant splenomegaly and the presence of large numbers of circulating myeloblasts in idiopathic myelofibrosis are reviewed.