Electron Microscopy Observation of Human Pulmonary Ultrastructure in Two Patients with High-Altitude Pulmonary Edema.

We examined the pulmonary ultrastructure in tissue from two patients with high-altitude pulmonary edema (HAPE) by electron microscopy. In one case, we found that neutrophils were trapped in pulmonary capillary lumen of alveolar-capillary wall and part of the cytoplasm of a neutrophil protruded and adhered to the capillary endothelium. There were several degranulated vacuoles in the cytoplasm of the neutrophil. The pulmonary capillary wall was deformed, thickened, and swollen and there was evidence of degeneration. In another case, infiltration of neutrophils and macrophages, proliferation of type II pneumocytes, and numerous red blood cells were also observed in alveolar air space. These electron microscopic ultrastructural observations illustrate for the first time damage to the pulmonary alveolar-capillary barrier in lung tissue of humans with advanced HAPE.