Promyelocytosis

Promyelocytosis is a term used in hematology to describe an overabundance of promyelocytes in the bone marrow or peripheral blood. Promyelocytes are immature white blood cells, specifically a stage in the development of granulocytes, a type of white blood cell that helps fight infection. Normally, promyelocytes are found in the bone marrow but are not typically present in significant numbers in the circulating blood.

The presence of a large number of promyelocytes, especially in the peripheral blood, is often a sign of a serious underlying condition, most commonly acute myeloid leukemia (AML). In AML, the bone marrow produces an excessive number of abnormal, immature white blood cells, including promyelocytes, which are unable to mature and function properly. These abnormal cells can crowd out healthy blood cells, leading to anemia, increased risk of infection, and bleeding problems.

While AML is the most frequent cause, promyelocytosis can sometimes be seen in other conditions, such as certain myelodysplastic syndromes or reactive conditions. Diagnosis typically involves a blood count and a bone marrow biopsy, where pathologists examine the cells to identify the specific type and number of promyelocytes. Treatment depends entirely on the underlying cause, with AML requiring aggressive chemotherapy.