A patient with a WBC count just over 100,000 is most likely suffering from which condition?

A white blood cell (WBC) count just over 100,000 typically indicates a condition where the body's immune system is significantly dysregulated. In particular, this level of leukocytosis is most commonly associated with leukaemia, a type of cancer that affects the blood and bone marrow, leading to the overproduction of abnormal white blood cells.

In patients with leukaemia, the body produces excessive and immature forms of white blood cells that can crowd out normal cells, impairing the immune response and leading to other serious health issues. Recognizing a WBC count in this range is crucial for diagnosis because it often points to a hematological malignancy, necessitating further investigation and treatment.

Leucopenia refers to a decreased WBC count, which is not applicable in this case. Polycythemia involves an increase in red blood cells rather than white blood cells, and an infection would typically cause a WBC count increase but not to such an extreme extent as seen in leukaemia.