Parasitic Infection Common Cause of Persistent Eosinophilia in Inner-City Patients

Parasitic infection is a common cause of unexplained, persistent eosinophilia in inner-city patients, according to study findings presented at the American College of Allergy, Asthma & Immunology (ACAAI) 2022 Annual Scientific Meeting, held November 10-14, in Louisville, Kentucky.

Prior studies have demonstrated that individuals who have persistent eosinophilia (ie, an absolute eosinophil count [AEC] of >500 cells/mL) are frequently not adequately assessed for the potential underlying causes. The present study involved 82 patients (72% female; 42% Hispanic; 32.5% Black; mean age, 50 [range, 15 to 97] years) from an inner-city allergy clinic found to have an AEC of more than 500 cells/mL on at least 2 occasions, but without an established cause.

The investigators found hypereosinophilia (ie, an AEC of >1500 cells/mL) was reported in 17% (14 of 82) of the participants, and that the highest AEC reported was 40,000 cells/mL. Comorbid conditions among the participants included allergic rhinitis in 80.4% (66 of 82), asthma in 53.6% (44 of 82), nasal polyposis in 12% (10 of 82), and eczema in 8.5% (7 of 82).

Overall, 30% (24 of 75) of the participants tested positive for some parasitic infection: T canis was reported in 25.3% (16 of 63), S stercoralis in 10.9% (8 of 73), both T canis and S stercoralis in 6% (4 of 63), and B hominis in 4% (1 of 23). Additionally, 1 participant had W bancrofti and 1 participant had S mansoni.

In all, 18 of the 24 patients with a parasitic infection received antiparasitic therapy. Posttreatment, AEC was measured in 9 of the patients treated, with eosinophilia demonstrating resolution in all of them.

Further, 23% (12 of 52) of the study population exhibited elevated immunoglobulin G4 (IgG4; >86 mg/dL), but none of the participants had evidence of any IgG4-associated disease. In addition, 7% (4 of 56) of the study population experienced elevated interleukin-5 (IL-5) levels (ie, >3 pg/mL). Of these 4 individuals with an elevated IL-5 level, 3 had a parasitic infection.

The researchers concluded that “Parasitic infection is a common cause of unexplained persistent eosinophilia in inner-city patients,” and that the “Role of elevated IL-5 in different causes of eosinophilia needs further investigation.”

This article originally appeared on Pulmonology Advisor.