Differential Diagnosis: Monocytosis

Julie Allen, BVMS, MS, MRCVS, DACVIM (SAIM), DACVP (Clinical), Durham, North Carolina

ArticleLast Updated October 20201 min readPeer Reviewed
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Following are differential diagnoses for patients presented with monocytosis.*

  • Chronic neutropenia

  • Granulocyte colony-stimulating factor administration

  • Increased endogenous or exogenous corticosteroids (especially in dogs)

  • Inflammation (eg, infectious vs noninfectious, acute vs chronic)

  • Monocytic or monoblastic leukemia (very rare)

  • Necrosis and/or tissue destruction (eg, from coccidioidomycosis or immune-mediated hemolytic anemia)

  • Paraneoplastic response with various tumors (associated with poor prognosis)

    • Lymphoma (ie, increased monocyte chemotactic protein; possible secretion of granulocyte-macrophage colony-stimulating factor)

    • Osteosarcoma

  • Recovery from acute bone marrow injury

    • Secondary to administration of a chemotherapeutic agent

    • Secondary to parvovirus infection (rare)

*Monocytopenia is not recognized as a clinically significant problem.