My mom is 66 and she has had low wbc count for more than a year. now as her wbc fell to 3.2, i am very worried. could it be a deadly desease. i do not know what to check for? she has not many symtoms. she only has fatigue. pls recommend me what to do?

You are right to be concerned: anyone with WBC at this low level needs comprehensive medical evaluation. With the low WBC count, I wonder if her red blood cells also are low, i.e. anemia, which if severe can cause fatigue. If her personal physician doesn't seem concerned or knowledgable, find a hematologist/oncologist (blood disease/cancer specialist). Good luck.