Lymphopenia Causes. The condition is caused primarily by an infection or a recent infection. It is also possible that the body is not capable of making or producing enough lymphocytes.There is also a possibility that a person’s lymph nodes trap the necessary amount of lymphocytes.ymphopenia Causes. The condition is caused primarily by an infection or a recent infection. It is also possible that the body is not capable of making or producing enough lymphocytes.