Respiratory Failure in a Middle-Aged Smoker
A 46-year-old man presents to the emergency department (ED) with shortness of breath on mild exertion, a nonproductive cough, and chest pain that worsens when he takes deep breaths. The symptoms have been progressively worsening for 10 days. He denies the production of blood when he coughs, and he has not had any weight loss, nausea, vomiting, or lightheadedness. He has no pain in his joints and no rash. He does not recall any recent viral infection, and he also denies any exposure to fumes, vapors, or excessive dust; however, the patient does admit to smoking about a pack of cigarettes per day. On physical examination, his temperature is 100.9°F (38.3°C), his blood pressure is 160/90 mm Hg, and his heart rate is 110 bpm. The patient is breathing rapidly, with a respiratory rate of 30 breaths/min, and his oxygen saturation is 85% while breathing room air. The patient has no jugular venous distention or peripheral edema in the extremities. He does not have any digital clubbing. Auscultation of his chest reveals crackles in the left lower base.An arterial blood gas (ABG) analysis taken while the patient is breathing room air shows a hemoglobin saturation of 80%, a partial pressure of oxygen of 48 mm Hg, a partial pressure of carbon dioxide of 35 mm Hg, and a pH of 7.50. On further laboratory investigation, the patient’s hemoglobin is 125 g/L (normal range, 136-173 g/L), his platelet count is 74 × 109/L (normal range, 166-383 × 109/L), and his white blood cell (WBC) count is elevated at 18.9 × 109/L (normal range, 4.8-10.5 × 109/L), with 83% granulocytes but no bands.A chest radiograph demonstrates an infiltrate in the left lower lobe (see Image 1).
The patient is admitted to the hospital. Despite aggressive treatment for hypoxemia, including empiric use of antibiotics and oxygenation with noninvasive ventilation, respiratory failure develops, requiring the patient to undergo endotracheal intubation and mechanical ventilation. A computed tomography (CT) scan of the chest shows bilateral patchy, ground-glass infiltrates of an unclear etiology (see Image 2). A diagnostic fiberoptic bronchoscopy with bronchoalveolar lavage and transbronchial biopsy demonstrates diffuse fibrotic changes. Stains and cultures of the samples obtained at bronchoscopy fail to reveal a pathogen as the cause of this patient’s respiratory process.
No definitive etiology is identified. To what group of disorders does this condition belong?
What is the diagnosis?