[Complete left lung atelectasis as the initial presentation of allergic bronchopulmonary aspergillosis: a case report].

This paper reports a case of allergic bronchopulmonary aspergillosis (ABPA) presenting with acute respiratory failure and complete left lung atelectasis on imaging. The patient had no prior history of respiratory disease and experienced a sudden onset of symptoms, with partial atelectasis of the left lung rapidly progressing to complete collapse. Significant clinical improvement was observed after bronchoscopic removal of a suspected "foreign body" from the left main bronchus, leading to an initial misdiagnosis of bronchial foreign body. However, one month later, follow-up imaging revealed a new shadow in the left upper lobe. Further investigation confirmed the diagnosis of ABPA caused by sensitization to <i>Aspergillus terreus</i>.The patient was treated with two courses of systemic corticosteroids combined with antifungal therapy, resulting in effective disease control. Over a six-year follow-up period, the patient maintained a favorable prognosis with no progression to late-stage pulmonary complications. Complete lung atelectasis-type ABPA poses significant diagnostic challenges in its early stages and remains rarely reported in the domestic literature, leading to a high risk of misdiagnosis or delayed diagnosis. This case report aims to raise clinical awareness and facilitate earlier recognition of this uncommon presentation among healthcare professionals.