Thanks to Jesse for presenting the case of an elderly woman with fever, multiple rash morphologies, and eosinophilia! The kind of case where every consultant gets involved. Pearls below!
Eosinophilia: Absolute eosinophil count > 500
Hypereosinophilia: Severe eosinophilia >1500
Hypereosinophilic syndrome: Hypereosinophilia on at least 2 occasions with end-organ dysfunction due to eosinophilia
Does the degree of eosinophilia aid in diagnosis? Only if extreme!
– Very mild eosinophilia may be asthma/allergic
– Very severe eosinophilia (>20,000) likely myeloproliferative neoplasm (primary hypereosinophilic syndrome)
Think of these categories of disease for eosinophilia:
– Medication effect (e.g. DRESS/DIHS)
– Transplant rejection
– Vasculitis (e.g. Churg-Strauss)
– Parasitic (strongyloides, toxocara, trichinella, schistosomiasis, filariasis, hookworm)
– Fungal infections (e.g. Aspergillus)
– Primary hypereosinophilic syndrome (myeloproliferative neoplasm)
Adrenal insufficiency (relatively rare compared to other causes)
Other (diseases with specific organ involvement)
– Interstitial nephritis
– Eosinophilic pneumonia
– Many others including eosinophilic GI diseases
*Pearl: Giardia, malaria, and babesia do NOT typically produce eosinophilia!
*Pearl: Eosinophilia + Fever is NOT generally due to bacterial or viral infection! These LOWER eosinophil counts!
*Pearl: Tissue damage is more likely at eosinophil counts >1500, but can also occur at lower levels!
Recommended workup for unexplained eosinophilia:
– CBC, diff, blood smear
– Chem, u/a, LFTs
– Troponin (cardiac infiltration)
– Strongyloides serology
– Vit B12 (elevated in myeloproliferative neoplasm)
– Flow cytometry for lymphocyte subsets
– Chest Xray
– Serum tryptase (mastocytosis or hypereosinophilic syndrome)
Can also send if appropriate:
– Molecular testing for hematologic disorders
– Immunoglobulin levels (autoimmune disease or immunodeficiency)
– Morning cortisol
– Stool O&P
– Viral serologies (e.g. HIV, HTLV)
– Serologies for specific parasitic infections (e.g. schistosomiasis)
– CT, lymph node biopsy