Rapidly progressive myelomonocytic leukemia (juvenile CML).

A rare type of rapidly fatal childhood leukemia, generally called juvenile chronic myelogenous leukemia, is characterized by absence of the Philadelphia chromosome and a predominantly monocytic proliferation, among other features. Unlike Philadelphia chromosome positive chronic myelogenous leukemia, this disease is neither chronic nor principally a disorder of granulocytic cell lines. A case is presented, with several clinical and laboratory parameters useful in establishing the correct diagnosis, and a change in terminology to "rapidly progressive juvenile myelomonocytic leukemia" is proposed.