Regardless of the etiology for restrictive lung diseases, many eventually lead to extensive fibrosis. The gross appearance, as seen here in a patient with organizing diffuse alveolar damage, is known as "honeycomb" lung because of the appearance of the dilated irregular air spaces between bands of dense fibrous connective tissue. In contrast, emphysema leads to loss of lung tissue with less support for keeping airways open, an obstructive lung disease.

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