Apparent Crazy Paving “Pulmonary Alveolar Proteinosis versus Hypersensitivity Pneumonitis”

Abstract

Interstitial lung disease (ILD) is an umbrella term for a large group of chronic disorders that involve the entire lung parenchyma as well as the alveolar interstitium. Fibrosis of the alveolar interstitium is a process common to all ILDs. It can be considered as a sequela of chronic alveolitis that produces a derangement of the alveolar structures and ultimately leads to loss of functional gas exchange units. Fibrosis may progressively cause lung stiffness, reducing the ability of the air sacs to capture and carry oxygen into the bloodstream and eventually lead to permanent loss of ability to breathe. It ultimately culminates in “end-stage lung disease”. ILD can be caused by exposure to hazardous chemicals, certain medications, and medical treatments. Diagnosis of ILDs is done by evaluation of patient through chest radiograph and high-resolution computed tomography (HRCT) features. At present, open or thoracic lung biopsy is gold standard for the diagnosis of ILDs. The “crazy-paving” pattern is a common finding nowadays at HRCT of lungs. It consists of diffuse ground-glass attenuation with superimposed interlobular septal thickening and intralobular lines resembling the structure of irregularly shaped paving stones. Crazy pavement in HRCT thorax is seen most commonly in acute respiratory distress syndrome, bacterial pneumonia, acute interstitial pneumonia and pulmonary alveolar proteinosis. Less common causes are drug-induced pneumonitis, radiation pneumonitis, pulmonary hemorrhage, chronic eosinophilic pneumonia, UIP, and pulmonary edema. We herein present a case of ILD with interesting HRCT pattern of crazy pavement pattern.