A systematic approach to patients with eosinophilia
Consider the following approach in the assessment of patients with eosinophilia seen in the ambulatory care setting. Inpatients or patients being seen in developing areas may require a modified approach.
History. All patients with eosinophilia should have a thorough history taken, with particular attention paid to travel history. A travel history should make note of dates, duration and location of travel, and any relevant exposures, such as arthropod bites or swimming in freshwater. Dietary habits, such as ingestion of seafood, game, or undercooked meat can also be helpful in making a diagnosis.3,4
Physical exam. In addition to a general physical examination, the following features may be helpful in determining the etiology of eosinophilia. Wheeze is characteristic of parasites in a lung migration phase (eg, strongyloidiasis and ascariasis) or asthma. Hepatomegaly can be seen with liver flukes, visceral larva migrans, or schistosomiasis. Periorbital edema can be observed with Trichinella infection. Loa loa, a type of filarial infection, produces a transient, migratory angioedema, often localized to the wrists and large joints (termed Calabar swelling). Dermatitis of varying intensity may suggest filarial infection, schistosomiasis, or atopy. Perianal dermatitis is observed with strongyloidiasis. Cutaneous larva migrans is characterized by a linear, serpiginous rash.3,4
Laboratory investigations. Investigation will vary depending on the patient’s history, exposures, exam findings, and degree of eosinophilia. Any patient who is unwell or has significant eosinophilia (≥3 x 109/L) may warrant more urgent referral to infectious disease, travel medicine, or hematology. Basic laboratory investigations should include a CBC with differential, routine serum chemistries, and liver enzymes. In the setting of significant eosinophilia, an electrocardiogram, cardiac enzyme levels, and a chest x-ray should be obtained to screen for end-organ damage related to eosinophilia.3-5
In patients in whom you suspect hematologic malignancy, bone marrow aspiration and biopsy are often needed to make the diagnosis.5
Parasitic infections are most often diagnosed on stool examination for ova and parasites or by serology. Stool should be collected on 3 separate days to increase diagnostic yield. Certain species of Schistosoma can also be diagnosed on direct microscopy of urine specimens. Serologic assays are available for schistosomiasis, strongyloidiasis, Toxocara, fascioliasis, filariasis, and Trichinella. Further investigations for filiariasis, including blood films, eye exam, and skin snips will vary with filarial species, so expert consultation should be considered.3,4
Our patients. The first patient with strongyloidiasis was treated with ivermectin 200 µg/kg/day orally for 2 days and experienced symptomatic improvement and resolution of eosinophilia. The second patient with ALL was admitted and referred to hematology and received induction chemotherapy. Treatment was well tolerated and the patient was discharged one week later, with appropriate follow-up.
THE TAKEAWAY
Eosinophilia is commonly encountered in primary care. The approach to eosinophilia and the differential diagnosis can be challenging. The correct diagnosis was reached in both cases by maintaining a broad differential diagnosis. Obtaining a travel and exposure history is fundamental, although noninfectious causes, including allergy, malignancy, and drug reaction, must always be considered.