This article is from the Interpretation Of Lab Test Profiles, by Ed Uthman firstname.lastname@example.org with numerous contributions by others.
Monocytosis is seen in the recovery phase of many acute
infections. It is also seen in diseases characterized by chronic
granulomatous inflammation (TB, syphilis, brucellosis, Crohn's
disease, and sarcoidosis), ulcerative colitis, systemic lupus,
rheumatoid arthritis, polyarteritis nodosa, and many hematologic
neoplasms. Poisoning by carbon disulfide, phosphorus, and
tetrachloroethane, as well as administration of griseofulvin,
haloperidol, and methsuximide, may cause monocytosis.
Monocytopenia is generally not a clinical problem.