Differential Diagnosis: Monocytosis

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.