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Desquamative Interstitial Pneumonia
Desquamative interstitial pneumonia is chronic lung inflammation characterized by mononuclear cell infiltration of the airspaces; it occurs almost exclusively in current or former cigarette smokers.
Desquamative interstitial pneumonia is a type of idiopathic interstitial pneumonia (see Overview of Idiopathic Interstitial Pneumonias). The vast majority of adult patients with desquamative interstitial pneumonia are smokers, who tend to develop the disease in their 30s or 40s. The disease tends to affect the lung parenchyma uniformly. The alveolar walls are lined with plump cuboidal pneumocytes; there is moderate infiltration of the alveolar septum by lymphocytes, plasma cells, and, occasionally, eosinophils. Alveolar septal fibrosis, if present, is mild. The most striking feature is the presence of numerous pigmented macrophages within distal airspaces, mistaken as desquamated pneumocytes when the disease was first described. Honeycombing is rare. Similar but much less extensive findings occur in respiratory bronchiolitis–associated interstitial lung disease (RBILD—see Respiratory Bronchiolitis–Associated Interstitial Lung Disease), leading to the suggestion that desquamative interstitial pneumonia and RBILD are different manifestations of the same disease caused by cigarette smoking.
Chest x-ray can show bibasilar hazy opacities without honeycombing, but is normal in up to 20% of cases. HRCT shows multifocal or diffuse, basilar, subpleural ground-glass opacities. Cysts may be present, often in areas of ground-glass opacity. Irregular linear and reticular opacities are common but are not usually the dominant features. Honeycombing may be visible, occurs in the minority of patients, and is usually limited. Surgical lung biopsy is sometimes necessary.
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