Following are differential diagnoses, listed in order of likelihood, for patients presented with basophilia. Of note, because basophilia is typically seen in association with eosinophilia, many of the differentials are associated more with eosinophilia. Basophilia alone is rare and, when noted, is often a paraneoplastic phenomenon.

• Parasitism (eg, Dirofilaria immitis, Acanthocheilonema reconditum, Aelurostrongylus abstrusus, Angiostrongylus vasorum, ticks)

• Hypersensitivity/allergic disease

• Idiopathic hypereosinophilic syndromes (eg, eosinophilic bronchopneumopathy)

• Paraneoplastic cause

  • Lymphoma

  • Mast cell neoplasia

  • Chronic myeloid leukemia

  • Essential thrombocythemia

  • Polycythemia vera

  • Miscellaneous tumors (eg, primary hepatic chondroblastic osteosarcoma in a cat)

• Basophilic leukemia

• Drug reaction

  • Heparin

  • Penicillin