Reconsidering isolated FEV1 reduction: A case report of early-stage asthma with bronchial hyperreactivity and literature review

Introduction: Isolated low forced expiratory volume in one second (FEV1) spirometric impairment (ILFSI) is characterized by a decreased FEV1 while both forced vital capacity (FVC) and the FEV1 /FVC ratio remain within normal ranges. This pattern may hide an underlying respiratory disorder that warrants further examination. Notably, the 2022 European respiratory society/American thoracic society (2022-ERS/ATS) guidelines do not classify ILFSI as pathological, a stance that has sparked some controversy. This teaching report discussed the case of a woman with ILFSI who developed mild bronchial hyperreactivity after undergoing a methacholine bronchial challenge test (MBCT) and exhibited positive skin prick tests (SPTs) for dust mites. Observation: A 28-year-old professional interior designer, who has no history of smoking or exposure to wood smoke and allergens, and who previously experienced a mild case of coronavirus disease-2019, consulted a pulmonologist for chronic cough, sputum production, and recurrent sneezing episodes. Asthma was suspected, leading to the performance of SPTs, spirometry, and either a bronchodilator test (in case of an obstructive ventilatory impairment) or MBCT (in case of a normal spirometry) as requested in the pulmonologist referral letter. The spirometry results indicated ILFSI, with a low FEV1 (z-score =-1.74, 79%) while FVC (z-score =-0.97, 88%) and the FEV1 /FVC ratio (z-score =-1.35) remained normal. According to the 2022-ERS/ATS guidelines, these findings are considered normal spirometry because of the maintained FVC and FEV1 /FVC ratio. The MBCT confirmed mild bronchial hyperreactivity, showing a 20% drop in FEV1 at a dose of 96 µg. Furthermore, SPTs were positive for dust mites (Dermatophagoides pteronyssinus and farinae). Conclusion: The results of this report suggested a possible association between ILFSI and early allergic asthma, indicating that ILFSI should be re-examined in future revisions of the 2022-ERS/ATS guidelines for interpreting spirometric tests.