An Exploratory Study Of A New Clinical Subtype Of Eosinophilic Granulomatosis With Polyangiitis(EGPA)

Objective:To identify a new subtype of eosinophilic granulomatosis with polyangiitis(EGPA)(previously known as Churg–Strauss syndrome)and to find more evidence for diagnosis of EGPA by comparison of clinic characteristics,airway inflammation,lung function,imaging findings and histologic findings between severe asthma and EGPA.Methods:We retrospectively reviewed the clinical records of severe asthmatics and EGPA patients diagnosed between January 2013 and April 2017 in the First Affiliated Hospital of Guangzhou Medical University.Laboratory and clinical parameters were compared between severe asthmatics,subjects with only respiratory system involved,?4 ACR criteria and had both lung and extra-pulmonary organ involved [excluding ear,nose & throat(ENT)](systemic EGPA).Unbised clustering based on principal components transformed was performed on clinical parameters to verify the new EGPA subtype.Results:1.We enrolled 54 patients with severe asthma,99 patients with EGPA.Compared with severe asthma,blood eosinophils(Eos)count and the percentage of blood Eos at initial diagnosis [(0.5±0.6 vs.1.0±1.0 vs.2.9±3.2 10^9/L,p<0.001),(5.9±6.5 vs.11.8±8.2 vs.21.7±18.5%,p<0.001)],blood Eos count and the percentage of blood Eos at past maximum record value [(0.5±0.6 vs.1.4±1.2 vs.4.2±4.9,p<0.001),(5.9±6.5 vs.16.1±7.8 vs.28.7±19.3%,p<0.001)],total Immunoglobulin E [188.0(77.1-417.0)vs.427.0(126.5-1078.0)vs.576.0(216.0-1607.0)k U/L,p=0.001] for EGPA were greater.Diffused ground-glass opacity,tree-in-bud opacities,bronchiectasis;mucoid impaction,increased small vascular markings,enlarged mediastina nodules and enlarged hilar nodules were significantly more frequent in EGPA than in severe asthma.More Eos infiltration of lung tissue(57.7% vs.88.1% vs.92.0%,p<0.001)and Eos infiltration in the vessel of lung tissue(0% vs.55.9% vs.28.0%,p<0.001)in EGPA than severe asthma.Bronchodilator response was lower in EGPA than severe asthma(22.4±17.2 vs.11.8±11.5 vs.7.7±10.0%,p<0.001).There were similar chest image fingding between subjects of EGPA with only respiratory system involved and systemic EGPA other than entrilobular nodules.2.Three principal components were identified.Principal component 1 was typified by increasing diffused ground-glass opacity,tree-in-bud,mucoid impaction with decreased lung markings.Principal component 2 was characterized by increasing hilar small nodules,enlarged mediastina nodules,and enlarged hilar nodules.Principal component 3 was associated with increased Eos at past maximum record value.Subjects of EGPA with only respiratory system involved was identified based on above 3 principle component.3.The expression level of serum cytokines in severe asthma is not consistent with that in EGPA,and can be identified by principal component analysis and cluster analysis.Conclusion:There is a population in asthma populations presenting only in respiratory system damage similar to EGPA patients.This population presented different clinical characteristics from severe asthmatics.Localized EGPA subtype was identified based on clinical parameter clustering.