The normal white blood cell count of Lymphocytes for newborns is 5,800 cells/µL. Lymphocytes count increases during the first year to 7000 cells/µL then it starts decreasing to reach 2500 cells/µL in adults.
Since Lymphocytes count increases during the early childhood, Lymphocytosis detection varies by age. For children from birth to 3 years old it is defined as the count of 9000 or more Lymphocytes/µL. From 4 to 12 years old, the threshold value is 7000 cells/µL, and 4000 cells or more per microliter for adults.
Abnormal increases in the Lymphocytes count can be caused by the same causes of Leukocytosis.
High Lymphocytes Count or Lymphocytosis can be cause by viral disorders such like Mumps, Rubella, Rubeola, Hepatitis, and Varicella.
Lymphocytosis occurs as a result of pertussis and Chronic Lymphocytic Leukemia.