Chronic Myelogenous Leukemia. CML is a disorder where too many granulocytes or myeloid cells, a type of white blood cell, are produced. This disease results in the abnormal accumulation of these cells in the marrow and the bloodstream and often the spleen. CML may occur at any age in either sex. It is uncommon before 10 years of age, and occurs at an average age of 45.