When allergy mimics catastrophe: allergic bronchopulmonary aspergillosis presenting as unilateral lung collapse with respiratory failure.

Allergic bronchopulmonary aspergillosis (ABPA) is a T helper 2 cell-mediated hypersensitive lung disorder in response to Aspergillus that usually affects asthmatic and cystic fibrosis patients. However, it rarely presents as lung collapse.We report a case of an elderly male who presented in the emergency department with respiratory distress, with oxygen saturation 80% with room air (RA). On evaluation with examination and radiology, the case was revealed as left lung collapse. Fibreoptic bronchoscopy revealed a huge mucus plug (MP) obliterating the left main bronchus, causing collapse of the entire left lung. The MP could not be completely removed by suction and was extracted with a cryoprobe. Post procedure, SpO2 improved to 99% RA with X-ray showing complete lung aeration restoration. A suspicion of ABPA was made. Aspergillus-specific IgE and IgG came positive, along with raised total IgE and peripheral eosinophilia. The patient was started on itraconazole and oral corticosteroids and discharged in stable condition.This case highlights that it is important to consider an MP with ABPA as a differential in cases of lung collapse after ruling out malignancy.