Eosinophilic granulomatosis with polyangiitis in allergic asthma: Efforts to make early diagnosis possible

Background: Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare autoimmune disease that can affect multiple organ systems in the body. A majority of patients with EGPA present with asthma-like symptoms and may be misdiagnosed with refractory asthma. It is necessary to distinguish EGPA from asthma and provide a theoretical basis for effective future prevention and treatment. Objective: This study aimed to compare the clinical features of EGPA and the clinical features of allergic asthma in an effort to make an early diagnosis possible. Methods: We reviewed the basic information, test results, pre-onset conditions, and prognosis of 44 adult patients with EGPA who were admitted to our hospital between January 2013 and June 2021, and conducted a 1:1 matched case-control study to compare patients with EGPA and patients with allergic asthma. Results: The 44 patients with EGPA were older than those with allergic asthma, but more than half of the patients with EGPA had been diagnosed with bronchial asthma, with a history of 10 months to 40 years, and had previously used inhalers or systemic steroids. The proportion of male-to-female cases was ∼1:1, with seven antineutrophil cytoplasmic antibodies (ANCA) positive cases (15.9%), 20 limited EGPA cases (45.45%), and 24 systemic EGPA cases (54.55%). Although the peripheral blood eosinophil count and percentage were lower in the male patients than in the female patients, male patients with higher five-factor scores might indicate worse prognosis. The fractional exhaled nitric oxide (FeNO) level, eosinophil percentage and count, and total immunoglobulin E (IgE) level were higher in the EGPA group than in the allergic asthma group. Unlike in allergic asthma, the FeNO level is not correlated with the blood eosinophil count or percentage in EGPA. Seven patients received cardiac emission computed tomography (ECT) tests, with abnormalities suggested in six patients. Results of an electrocardiogram, color-Doppler echocardiography, myocardial enzyme level, and troponin level suggested no obvious abnormality. Conclusion: The proportion of patients with EGPA who tested positive for ANCA is not high, and patients with high eosinophil counts should be alert to the possibility of having EGPA. For patients with infiltration of eosinophils into the airway, a diagnosis should not be based on peripheral blood eosinophil counts. It is recommended that the FeNO level and pulmonary function should also be monitored for patients who present with symptoms in other body systems. The sensitivity of cardiac ECT tests is higher than routine tests, so timely screening by cardiac ECT is recommended for all patients with EGPA.