Elevated Carcinoembryonic Antigen and Eosinophilia: An Unclear Relationship in a Patient With Allergic Bronchopulmonary Aspergillosis

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Abstract Intro: Allergic bronchopulmonary aspergillosis (ABPA) is a hypersensitivity response to Aspergillus colonization in the airways characterized by recurrent asthma exacerbations including symptoms of productive cough, mucus plugging, and dyspnea. The biomarker carcinoembryonic antigen (CEA) is classically used to diagnose and monitor tumor progression, especially breast and gastrointestinal cancers. We present a case of ABPA in a patient with previous rectal malignancy whose elevated eosinophilia and CEA levels improved with the use of the interleukin-5 (IL-5) monoclonal antibody mepolizumab. Case Description: Our patient is a 71 year old female with a history of anal squamous cell carcinoma (treated with Nigro protocol in 2016) who first presented in 2017 with acute onset dyspnea, wheezing, and chest congestion. Symptoms persisted intermittently through 2017-2021 with no significant improvement with inhaled corticosteroid (ICS) and short-acting beta agonist (SABA) use, but transiently improved with short courses of oral corticosteroids. In January 2022 she represented with worsening productive cough and dyspnea, however due to her osteoporosis, she declined glucocorticoids. At that time lab work was notable for eosinophilia and elevated serum IgE while imaging demonstrated bronchiectasis, mucus plugging, and bibasilar tree-in-bud opacities. With these findings, she was started on a 3 month trial of mepolizumab that temporarily improved her symptoms, however these recurred shortly after discontinuation. Additionally, while undergoing routine surveillance for cancer recurrence in early 2022, she was found to have elevated serum CEA levels. Subsequent work-up, including colonoscopy, was negative for cancer recurrence. She returned in early 2023 for persistent pulmonary symptoms with associated eosinophilia at which time she was begun on an extended course of mepolizumab. She subsequently had significant improvement in her symptoms, with associated decline in eosinophils and CEA levels. Discussion: Cases of elevated CEA in patients with eosinophilia and without evidence of malignancy have been reported in the literature. These cases, including both pulmonary and systemic diseases, demonstrate a positive correlation between CEA levels and serum eosinophils. While most case reports described treatment with oral corticosteroids, our patient declined corticosteroid treatment and was therefore subsequently treated with mepolizumab. CEA and eosinophils declined as her symptoms improved with mepolizumab, demonstrating that this medication like corticosteroids can be effectively utilized for long term management. There have been several proposed pathophysiological mechanisms to explain the relationship between CEA and eosinophils, however more investigation is required to better understand their association in ABPA.

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