Eosinophilia

Background

• Any eosinophil count over 0.5
• Graded as mild (0.5 to 1.5), moderate (1.5 to 5), and severe (more than 5)
• Hypereosinophilia may refer to eosinophils greater than 1.5, which is high enough that the eosinophils can cause tissue damage regardless of underlying trigger
• May be primary (either eosinophilic hematologic malignancy or idiopathic) or secondary/reactive

Differential Diagnosis

• Hematologic
  • Primary: eosinophilic leukemia, CMML, hypereosinophilic syndrome
  • Secondary: Non-Hodgkin lymphoma and Hodgkin lymphoma
• Infectious
  • Parasitic infections
    • Strongyloides stercoralis, hookworms, schistosomiasis, and scabies (most common)
    • Tropical pulmonary eosinophilia from filarial roundworms (Wuchereria bancrofti and Brugia)
    • Many others
      • Protozoa: Isospora belli, Dientamoeba fragilis, Sarcocystis
      • Filarial nematodes: Onchocerca, lymphatic filariasis, tropical pulmonary eosinophilia, Loa loa, Mansonella
      • Non-filarial nematodes: Strongyloides stercoralis, hookworms, whipworm, Ascaris, Trichinella, Toxocara, Gnathostoma, Angiostrongylus cantonensis, Anisakidosis
      • Cestodes: Sparganosis
      • Trematodes: Fasciola, Paragonimiasis, Schistosoma
      • Scabies
  • Viruses: HIV, HTLV
  • Bacteria: Bartonella, Borrelia, syphilis, scarlet fever (resolving)
  • Mycobacteria: tuberculosis, Hansen disease
  • Fungi: ABPA, Coccidiodes, Histoplasma, Paracoccidioides, Cryptococcus
• Inflammatory
  • Eosinophilic pneumonia
  • Eosinophilic esophagitis
  • Eosinophilic myositis
  • Eosinophilic granulomatosis with polyangiitis (eGPA or Churg-Strauss)
• Endocrine
  • Addison disease
• Allergy
  • Atopy
  • Asthma
  • Drugs
    • Hypersensitivity reaction to NSAIDs, antibiotics, allopurinol, aromatic anticonvulsants, sulfasalazine, TMP-SMX, PPIs, vancomycin
    • Drug reaction with eosinophilia and systemic symptoms (DRESS)

Investigations

• CBC
• Stool for ova and parasites (specifically for helminths rather than protozoa)
• Strongyloides serology, +/- Schistosoma serology
• ANCAs
• Review current medications