(1) Infectioninfectious mononucleosis, hepatitis, cytomegalovirus, rubella, pertussis, tuberculosis, brucellosis, syphilis; (2) endocrine disordersthyrotoxicosis, adrenal insufficiency; (3) neoplasmschronic lymphocytic leukemia (CLL), most common cause of lymphocyte count >10,000/µL.
Section 6. Hematology and Oncology