Causes of lymphocytosis (> 4000/cumm in adults, > 7200/cumm adolescents, > 9000/cumm in children and infants)
Infection (Pertusis, infectious, lymphocytosis, infectious hepatitis, cytomegalovirus (CMV) infections, mumps, rubella, varicella, toxoplasmosis, chronic tuberculosis),
Others like thyrotoxicosis,
Addison's disease,
neutropenia with relative lymphocytosis,
lymphatic leukemia,
Crohn's disease,
ulcerative colitis and
infancy (normal count 40- 60 %) called relative lymphocytosis.
