Leucoblastic blood count

A leukoblastic blood count refers to the presence of precursors of granulopoiesis in the peripheral blood. This is always pathological, regardless of the percentage (Alpay 2019).

Normally, cellular elements do not leave the bone marrow until they have reached a certain stage of maturation. In extramedullary myelopoiesis, however, even immature precursors of granulopoiesis—such as metamyelocytes, myelocytes, myeloblasts, or promyelocytes (Antwerpes 2018)—enter the peripheral blood. This is referred to as a leukoblastic blood count (Herold 2025).

In addition to the precursors of leukopoiesis, precursors of erythropoiesis—such as normoblasts, proerythroblasts, and erythroblasts—can also enter the peripheral blood. This is then referred to as a leukoerythroblastic blood count (Antwerpes 2018).

Possible causes for the presence of nucleated precursor cells in the peripheral blood include:

• Bone metastases
• Myeloproliferative disorders
• Extramedullary hematopoiesis (Antwerpes 2018)

• Splenomegaly
• Reduced performance (Latus 2025)
• Fever
• Night sweats
• Cachexia (Girndt 2023)

1. Alpay N, Oduncu F (2019) Cases in Hematology and Oncology: Tricky Clinical Courses for Medical Detectives. Elsevier Urban & Fischer Verlag 95
2. Antwerpes F (2018) Leukoerythroblastic Blood Count. Doc Check Flexikon. https://flexikon.doccheck.com/de/Leukoerythroblastisches_Blutbild
3. Girndt M, Michl P (2023) Internal Medicine² Elsevier Urban & Fischer Publishers, Germany, pp. 224–225
4. Herold G et al. (2025) Internal Medicine. Herold Verlag 66
5. Kasper D. L., Fauci A. S., Hauser S. L., Longo D. L., Jameson J. L., Loscalzo J., et al. (2015) Harrison’s Principles of Internal Medicine. McGraw-Hill Education
6. Latus J, Alscher M D (2025) Board Exam in Internal Medicine: 2,800 Annotated Exam Questions. Question 72