Atypical chronic myeloid leukemia (aCML) is a rare type of leukemia that shares many similarities with chronic myeloid leukemia. It is a myeloproliferative and myelodysplastic disease.
Atypical chronic myeloid leukemia (aCML) is a rare type of leukemia that is thought to arise from the uncontrolled proliferation of multipotent stem cells. It is a disease that causes the accelerated production of immature blood cells of the myeloid lineage. Typically, it occurs in the elderly who are above the age of seventy  . Its incidence is unknown, and recorded cases show equal distribution between males and females.
The symptoms of aCML are largely the same as those found in chronic myeloid leukemia (CML), and these include anemia and its manifestations, such as pallor, dyspnea, and fatigue . Furthermore, patients may present with splenomegaly or hepatomegaly . Many of the symptoms are non-specific and include malaise, fever, weight loss, and headaches. More specific phenomena are easy bruising and bleeding diatheses. Some cases of aCML may be asymptomatic at the time of diagnosis.
The difference between aCML and CML is marked by certain genetic variations, notably the lack of the Philadelphia chromosome in aCML, although the two also have genetic similarities  .
Definitive diagnosis, therefore, can only be made after a peripheral blood smear and bone marrow aspirate are conducted. aCML is both myelodysplastic and myeloproliferative, producing immature cells in large numbers. In general, both bone marrow and blood samples will show elevated levels of white blood cells, granulocytes in particular . As a direct result of this overproduction, bone marrow production of normal blood cells in numerous cell lineages is suppressed, leading to the aforementioned symptoms.
The survival rate for the majority of patients is less than two years . Moreover, among those with aCML, up to 40% demonstrate a conversion of the disease to acute leukemia  . A poor prognosis is marked by severe anemia, as well as a low platelet count . Complications of aCML include infections, cerebral hemorrhage due to low platelets, as well as organomegaly and refractory leukocytosis  .
Diagnosis is based on laboratory studies more than clinical presentation. The two components studied are blood composition and bone marrow analysis. A peripheral smear is routinely taken, commonly revealing elevated leukocytes of more than 13 000 cells per microliter, anemia, and thrombocytopenia. White cell counts may exceed 300 000 cells per microliter  . Upon further inspection, a proportion of these, usually less than 20%, are blast cells. The bone marrow results will show a hypercellularity as well as an elevated blast cell count. The dysplastic white cells display cytoplasmic and nucleic abnormalities, such as a pseudo Pelger-Huet anomaly and abnormal lobulation of nuclei. Distinguishing aCML from CML is done via cytogenetics, where the former does not show changes such as a Philadelphia chromosome .