Neutropenia is a condition characterized by an abnormally low count of neutrophils, a type of white blood cell essential for fighting bacterial infections. It is a common side effect of cancer treatments like chemotherapy. Managing neutropenia involves regular blood tests to monitor WBC levels, administering growth factors (e.g., filgrastim) to stimulate WBC production, and taking precautions to avoid infections, such as practicing good hygiene and avoiding crowds.