Could the disease leukopenia lead to leukemia?

Possibly. There are a lot of reasons for leukopenia. Usually isolated low white cells is not a sign of leukemia if the red blood cells and the platelets also found in blood are fine. Leukopenia develops in leukemia because all the bone marrow cells that eventually end up in the blood stream are crowded out by leukemia cells.
See below. Leukopenia is a decrease in the white blood cell (WBC) count. It does not lead to leukemia but can be a manifestatiin of leukemia even though leukemia is usually associated with high wbc.