Histologic Changes

In addition to the black pigment in the interstitium, there are frequent collections of alveolar macrophages filled with black pigment. The pigment is coarsely granular, and particles vary in size. It is not the light-brown pigment found in cigarette smokers, and no birefringent crystals, often seen in such smokers, were found with it. It did not have the coarse, refractile appearance of hemosiderin, and it did not stain with an iron stain.

Lavage fluid from another patient with the same pigment shows that most of the macrophages contain some pigment. The fluid was visibly black.

Clinical summary Discussion

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