Acute respiratory failure as a rare presentation of non-fibrotic hypersensitivity pneumonitis: Case series

RATIONALE: Hypersensitivity pneumonitis (HP) is an increasingly recognized interstitial lung disease caused by exposure to inhaled, mostly organic, antigens. The non-fibrotic type of HP generally follows a benign course. We present 3 patients with a rare presentation of non-fibrotic HP-acute respiratory failure. PATIENT CONCERNS: 2 females and 1 male, presented to the pulmonary department due to resting dyspnea, cough and low-grade fever. Arterial blood gases revealed profound hypoxemia. No relevant abnormalities were found in the blood tests. In high-resolution computed tomography (HRCT), signs of extensive interstitial lung disease were present. Infection was excluded based on genetic testing and cultures. Pulmonary function tests revealed decrease in forced vital capacity (FVC) and transfer factor of the lungs for carbon monoxide (TLco). DIAGNOSES: Non-fibrotic HP was diagnosed based on positive exposure to organic antigens, characteristic lung HRCT pattern, and bronchoalveolar lavage lymphocytosis (in 2 cases). INTERVENTIONS: Oxygen therapy was implemented through the nasal tube, accompanied by intravenous and subsequently oral steroids, gradually tapered. OUTCOMES: Rapid clinical improvement, near-complete regression of interstitial lung disease, significant increase in lung volumes and lung transfer factor for carbon monoxide were observed and maintained with low-dose therapy. LESSONS: Non-fibrotic HP rarely presents as a life-threatening interstitial lung disease, requiring immediate immunosuppressive treatment. In some patients with extensive lung involvement, prolonged steroid therapy is necessary to achieve complete resolution of lung opacities and clinical improvement.