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Updated: Nov 3, 2025
Author Spotlight: Investigating the Pathophysiology of Eosinophilic Esophagitis
Published on: May 10, 2024
The causes of a peripheral blood eosinophilia in a secondary care setting
Andrew John Wardlaw1, Sarah Wharin2, Hnin Aung1
1Department of Respiratory Sciences, College of Life Sciences, Institute for Lung Health, NIHR Leicester Biomedical Research Centre (Respiratory theme), University of Leicester and Respiratory and Allergy Services, University Hospitals of Leicester NHS Trust, Leicester, UK.
Background:
A peripheral blood eosinophilia of greater than 1.0 × 109 /L is relatively unusual and offers a clue to the underlying diagnosis. In 2003, we established a specialist service to diagnose unexplained eosinophilia.
Objective:
To describe the causes of an eosinophilia in our service and the diagnostic algorithm we developed.
Methods:
Subjects were referred by physician colleagues across a range of specialties and undertook standard investigations following a semi-structured protocol. Data were extracted from a bespoke database.
Results:
Three hundred and eighty two subjects were referred over a 17-year period. Average age was 54 years and 183 (48%) of subjects were female, with 21 of 25 (84%) females in the idiopathic eosinophilic pneumonia group (p < 0001), 22 of 30 (73%) females in the gastrointestinal disease group (p < .008), but 11 of 37 (30%) females in the eosinophilic granulomatosis with polyangiitis group (p < .04). A diagnosis was assigned after systematic evaluation using a pre-defined algorithm in 361 (94.5%) of cases. Fungal allergy (82 subjects: 21%), parasitic infection (61 subjects: 16%) and severe eosinophilic asthma (50 subjects: 13%) were the three commonest individual diagnoses. Hypereosinophilic syndrome (HES) disease including eosinophilic granulomatosis with polyangiitis (EGPA) accounted for 85 subjects (20%) of which seven subjects (2%) had myeloproliferative disease (M-HES). A high IgE was common, and 79 (91%) of subjects with complete data who had an IgE of ≥1000 IU/L had fungal allergy or parasite infection. The serum tryptase was raised in 44 of 302 (14.5%) of individuals across all diagnostic groups, though none had mastocytosis.
Conclusion:
A diagnosis of an unexplained eosinophilia can usually be determined using as semi-structured algorithm. Parasitic infection and fungal allergy often with severe eosinophilic asthma were common causes, whereas HES, particularly myeloproliferative, disease was relatively rare.
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