Eosinophilia

The New England Journal of Medicine published an interesting case report this past week (http://www.nejm.org/doi/pdf/10.1056/NEJMcpc1302331) from Massachusetts General Hospital about a 27 yo male that presented with diarrhea, fatigue and eosinophilia. I was humbled while going through the differential diagnosis and therefore, I wanted to write a blog post on to refresh myself on the topic of Eosinophilia. 

A wide variety of medical conditions can cause eosinophilia. The level of eosinophils in the blood will be different depending on the medical condition. As a result, it has been difficult to establish solid parameters that will define eosinophilia but uptodate states the following measurements

• Mild eosinophilia - 500-1500 cells/microL
• Moderate - 1500-5000 cells/microL
• Severe - >5000 cells/microL

Uptodate also defines the following

• Hypereosinophilia - eosinophils > 1500 cells/microL and can cause tissue and organ damage regardless of the cause
• Hypereosinophilia syndrome - eosinophils > 1500 in the absence of a discernable cause such as allergy, drug, parasite and HIV

Categories of Eosinophilia

• Primary - when eosinophilia occurs due to a problem with the progenitor cells/bone marrow and there is evidence of clonal expansion (lymphoid leukemias, myeloid leukemias)
• Secondary - when eosinophilia occurs due to a problem outside the progenitor/bone marrow cells such as parasites, drug sensitivity, allergies, autoimmune disease, metastatic cancer, Hodgkin's lymphoma and endocrine disease (adrenal insufficiency)

H & P 

• Medications both recent and current list?
• Recent travel? Where?
• Constitutional symptoms - fevers, chills, night sweats and weight loss
• Diarrhea? 
• Rash?
• Hx of allergies?
• Hx of autoimmune disorder?

Causes of Eosinophilia 

• Atopic Dermatitis
• Asthma
• Allergic rhinitis
• Esophagitis
• Gastritis
• Colitis
• Medications - eosinophilia alone is not enough to stop the medication unless there is evidence of end organ damage (most commonly involved are the lungs, kidneys and heart)
• Parasites - Strongyloides stercoralis, hookworm, filariae, and Toxocara canis and schistosomes Note: In contrast to infections with multicellular helminthic parasites, infections with single-celled protozoan parasites (Giardia lamblia and Entamoeba histolytica) do NOT characteristically elicit blood eosinophilia. The only exception is Dientamoeba fragilis and Isospora belli. 
• Fungal - Aspergillosis and coccidiodomycosis
• HIV - usually due to one of the following reasons and not the actual virus itself
• Leukopenia - may lead to percentage of eosinophils and not absolute increase in eosinophil
• Medications - pt may have reaction with medication against opportunist infections
• Adrenal insufficiency - occurring from cytomegalovirus causing adrenal failure
• Eosinophilic folliculitis - can be seen in pt with HIV
• Hematologic and Neoplastic Disorders
• Mastocytosis - characterized by proliferation of mast cells in various organs such as the skin, liver, spleen, bone marrow, and lymph nodes
• Leukemia - AML has a subtype called Acute eosinophilic leukemia
• Tumors - non-keratinizing cervical tumors, lung carcinomas, squamous carcinomas of the vagina, penis, skin, and nasopharynx, adenocarcinomas of the stomach, large bowel and uterine body, and transitional cell bladder carcinoma can all cause eosinophilia
• Rheumatic Disease 
•  eosinophilia-myalgia syndrome 
• idiopathic eosinophilic synovitis
• vasculitis - churg strauss
• Adrenal Insufficiency - glucocorticoids will exert eosinopenic effects by causing apoptosis. When there is adrenal insufficiency, there is a decrease in glucocorticoids which will cause an increase in eosinophils
• Immunodeficiency states - hyper IgE