Eosinophil-associated diseases: the allergist's and clinical immunologist's perspective

Summary

Eosinophil-associated diseases (EADs) refer to heterogeneous conditions in which eosinophils are believed to play critical pathological roles. They encompass common respiratory conditions, such as asthma, chronic rhinosinusitis with nasal polyps (CRSwNP), less common primary eosinophilic disorders of gastrointestinal tract, and rare conditions including eosinophilic granulomatosis with polyangiitis (EGPA) and hypereosinophilic syndrome (HES). A literature search was carried out in January 2024 in the MEDLINE and Scopus databases using the PubMed search engine (PubMed, National Library of Medicine, Bethesda, MD). We focused on blood eosinophilia and hypereosinophilia. A diagnostic workup is proposed. From allergist's point of view, we focused the review on 4 groups of eosinophilic disorders of specific interest. Our increased understanding of type 2 inflammation and biology has recently led to development of highly effective precision targeted therapies that are now approved for a growing number of eosinophilic disorders. Novel targeted biologics have a major impact on treatment strategies and have resulted in major advances in our understanding of the pathogenesis of these disorders. In the context of EADs, according to the heterogeneity of eosinophilic disorders a multidisciplinary approach should be adopted. Allergists and Clinical Immunologists play an important role as they have a clear understanding of the eosinophilic inflammation and the role of cytokines and are trained to recognize and characterize type 2 (T2) inflammation and its associated pathologies.

Recalcitrant course of bullous pemphigoid indicating coexisting hypereosinophilic syndrome: A case report and literature review

Key Clinical Message

As dermatologists, we must be aware that even limited localized lesions may signal a life-threatening condition, for which early diagnosis and treatment can improve the prognosis.

Abstract

Bullous pemphigoid is an autoimmune disorder characterized by blister formation. Hypereosinophilic syndrome is a myeloproliferative disorder featuring papules, nodules, urticarial lesions, and blisters. The coexistence of these disorders may highlight the involvement of common molecular and cellular factors. Here, we describe a 16-year-old patient with hypereosinophilic syndrome and bullous pemphigoid.

Distinct features of hypereosinophilic syndrome with neuropathy from eosinophilic granulomatosis with polyangiitis

BACKGROUND AND OBJECTIVES

Hypereosinophilic syndrome (HES) and eosinophilic granulomatosis with polyangiitis (EGPA) have overlapping clinical considerations, which frequently involve peripheral neuropathy. The current study aimed to discriminate between the clinicopathological features of HES and EGPA, focusing on the mechanism of peripheral nerve damage.

METHODS

A total of 53 patients who underwent nerve biopsies at our laboratory were examined: nine patients with idiopathic HES (iHES), three patients with reactive HES, 14 patients with myeloperoxidase-anti-neutrophil cytoplasmic antibody (ANCA)-positive EGPA, and 27 patients with negative EGPA. Nerve biopsies were performed using light and electron microscopy.

RESULTS

Polyneuropathy was more common than mononeuritis multiplex in iHES, which differed from that in ANCA-negative EGPA groups (p = 0.012). Nerve biopsies showed that iHES was associated with neuropathy features such as rare vasculitis and non-vasculitic eosinophilic infiltrates, which differed from those of ANCA-negative EGPA. Fibrinoid necrosis was found only in the reactive HES and ANCA-positive groups. The percentage of endoneurial vessels occluded with eosinophils tended to be higher in iHES (1.8%) than in ANCA-positive EGPA (0%) and negative EGPA (0.7%). In a patient with ANCA-negative EGPA, the endoneurial vessels were occluded with platelets, fibrinoid materials, and eosinophils, demonstrating the morphology of eosinophil extracellular traps.

CONCLUSION

iHES with neuropathy showed a pattern more similar to polyneuropathy than mononeuritis multiplex, which is dominant in ANCA-negative EGPA, and tended to show vasculitis in the peripheral nerves less frequently compared with EGPA. Eosinophilic infiltration and endoneurial vascular occlusion by eosinophils may cause nerve damage.

Aortic stiffness is increased in patients with hypereosinophilic syndrome being in early necrotic phase

Background

Persistent eosinophilia and eosinophil-mediated single- or multiple-organ damage are typical features of hypereosinophilic syndrome (HES). Theoretically, eosinophilic infiltration of the ascending aortic wall could not be excluded in HES, therefore the present study aimed to test whether HES is associated with abnormalities in aortic elastic properties.

Methods

The present study comprised 10 HES patients (mean age: 57.6±10.1 years, 5 males) without known cardiovascular disease, their results were compared to 19 age-, gender- and risk factor-matched controls (59.2±4.2 years, 15 males). Complete two-dimensional Doppler echocardiography with measurement of echocardiographic aortic elastic properties was performed in all HES cases and controls.

Results

Although neither systolic (30.6±3.4 vs. 30.1±3.6 mm, P=ns), nor diastolic (28.7±3.6 vs. 27.8±3.2 mm, P=ns) aortic diameter differed significantly between HES patients and matched controls, significantly increased aortic stiffness index (11.19±5.65 vs. 7.04±2.97, P<0.05) could be demonstrated in HES patients.

Conclusions

Increased aortic stiffness could be demonstrated in HES patients in their early necrotic phase.