THE SIGNIFICANCE OF MEGAKARYOCYTES IN THE PERIPHERAL CIRCULATION

1. Leuko-erythroblastic anemia, with leuko-erythroblastosis, rather than anemia, when associated either with the presence of megakaryocytes or giant platelets in the circulation, is very suggestive of the myeloid metaplasia so commonly found with myelofibrosis.

2. Associated splenomegaly with subsequent slow progress to hepatomegaly and a tendency to hypertension are confirmatory clinical features.

3. Sternal puncture may or may not confirm the diagnosis, but if the specimen contains megakaryocytes, the fact is highly significant. Difficulty in piercing the bone or in obtaining a satisfactory marrow sample are points in favor of a myelofibrosis, which should be confirmed by the histologic examination of a trephined specimen.

4. Controlled radiologic examination of the bones is sometimes of value in establishing a diagnosis in the idiopathic disease.

5. A similar blood picture may occur with polycythemia vera, with myeloid leukemia and, occasionally, with other conditions in which invasion of the bonemarrow occurs. In polycythemia vera the finding suggests a terminal phase of exhaustion; in myeloid leukemia, likewise, the megakaryocytic phenomenon is usually an ominous sign of the terminal phase.

6. When megakaryocytes are found in the circulation a diagnosis of myelofibrosis should always be considered.