Eosinophil Count

Aka: Eosinophil Count, Eosinophil, Eosinophilia

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II. Physiology

  1. Maturation
    1. Forms in Bone Marrow from Myeloblasts as with other Granulocytes (Basophils, Neutrophils, Monocytes)
    2. Matures in Bone Marrow over 8 days
    3. Moves to peripheral blood where it spends 8-12 hours
    4. Moves to target tissue where it spends 1-2 weeks
  2. Function: Response to Allergy and Parasitic Infection
    1. Responds to Mast Cell, Basophil chemotactic factors
    2. Type 1 Hypersensitivity Response - Late Phase (hours after exposure)
    3. Phagocyte (engulfs extracellular pathogens)
    4. Parasite (e.g. Helminth) response
    5. Antigen Presenting Cell
  3. Eosinophil granule contents (Proteins)
    1. Antiparasitic Agents with tissue toxicity effect
      1. Major Basic Protein (MBP)
      2. Eosinophil Cationic Protein (ECP)
      3. Eosinophil Peroxidase (EPO)
    2. Neurotoxins
      1. Eosinophil-Derived Neurotoxin (EDN)
      2. Eosinophil Peroxidase (EPO) - also listed above
    3. Markers of Eosinophil activity in Asthma
      1. Major Basic Protein (MBP) - also listed above
      2. Eosinophil Cationic Protein (ECP) - also listed above
    4. Other Proteins
      1. Charcot-Leyden Crystals
      2. Lysophosphatase
      3. Cytokines
  4. Surface Receptors
    1. IgE Receptors
      1. IgE-Antigen complex binding results in Eosinophil activation and degranulation
    2. IgG Receptors
    3. Complement Receptors

III. Labs: Morphology on Blood Smear

  1. Granulocyte stains brightly with Eosin Stain (due to Major Basic Protein or MBP)
  2. Bilobed nucleus
  3. Diameter: 12-17 microns

IV. Interpretation: Normal

  1. Range: 1-4% of peripheral blood cells

V. Types: Eosinophilia

  1. Familial Eosinophilia (Familial Hypereosinophilic Syndrome)
    1. Rare autosomal condition (most Hypereosinophilic Syndromes are not inherited)
  2. Acquired
    1. Primary Eosinophilia
      1. Idiopathic
        1. Hypereosinophilic Syndrome (>1500 Eosinophils/uL x6 months without known cause)
      2. Clonal Eosinophilia
        1. Acute Myeloid Leukemia and other malignancies (see below)
    2. Secondary Eosinophilia
      1. See below

VI. Causes: Increased (Eosinophilia)

  1. See Hypereosinophilic Syndrome
  2. Allergy
    1. Allergic Rhinitis
    2. Atopy
    3. Asthma
  3. Dermatologic Disorders
    1. Pemphigus
    2. Pemphigoid
    3. Polyarteritis Nodosa
  4. Parasitic or Tropical infection (esp. worm infestation)
    1. Trichinosis
    2. Aspergillosis
    3. Hydatidosis
    4. Angiostrongylus
    5. Ascaris lumbricoides
    6. Capillariasis
    7. Cysticercosis
    8. Echinococcus
    9. Fascioliasis
    10. Filariasis
    11. Gnathostomiasis
    12. Paragonimiasis
    13. Schistosomiasis
    14. Strongyloidiasis
    15. Toxocara
    16. Trichuris trichiura
  5. Bacterial Infection
    1. Scarlet Fever
    2. Leprosy
  6. Viral Infection
    1. Human Immunodeficiency Virus (HIV)
    2. West Nile Virus
  7. Fungal Infection
    1. Allergic Bronchopulmonary Aspergillosis (ABPA)
  8. Myeloproliferative disorders and other Malignancies (primary clonal Eosinophilia)
    1. Chronic Myelogenous Leukemia
    2. Hodgkin's Lymphoma
    3. Non-Hodgkin's Lymphoma
    4. Polycythemia Vera
    5. Myelofibrosis
  9. Collagen-vascular diseases
    1. Rheumatoid Arthritis
    2. Periarteritis
    3. Systemic Lupus Erythematosus
    4. Eosinophilia-Myalgia Syndrome
      1. Linked to L-Tryptophan and 5-Hydroxytryptophan (5-HTP) usage in 1989 (suspected contaminant)
  10. Medications
    1. Antibiotics
      1. Ampicillin
      2. Penicillin
      3. Minocycline
      4. Nitrofurantoin
      5. Erythromycin
      6. Sulfonamides
    2. NSAIDS and antiinflammatory agents
      1. Acetylsalicylic Acid (Aspirin)
      2. Ibuprofen
      3. Naproxen
      4. Methotrexate
    3. Psychiatric Agents
      1. Imipramine
      2. Trazodone
      3. Fluoxetine (Prozac)
    4. Miscellaneous
      1. Chlorpropamide (hypoglycemic agent)
      2. Procarbazine (Chemotherapy)
  11. Miscellaneous
    1. Radiation Therapy
    2. Eosinophilic Gastroenteritis
    3. Sarcoidosis
    4. Addison's Disease
    5. Loffler's Syndrome

VII. Evaluation: Eosinophilia (Eosinophils >500/mm3)

  1. See Leukocytosis
  2. History and potential causes
    1. Travel history
    2. New medications
  3. Diagnostics (consider)
    1. Dermatitis biopsy (if present)
    2. Consider allergy and immunology Consultation or testing
    3. Consider Parasite testing (e.g. stool Ova and Parasites)

VIII. References

  1. Mahmoudi (2014) Immunology Made Ridiculously Simple, MedMaster, Miami, FL
  2. Saiki in Friedman (1991) Medical Diagnosis, p. 227
  3. Abramson (2000) Am Fam Physician 62(9):2053-60 [PubMed]
  4. Riley (2015) Am Fam Physician 92(11):1004-11 [PubMed]

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