Arachnoid nodules in the lungs of high altitude Indians.

BACKGROUND Nodules of cells showing a striking histological similarity to those of arachnoid villi have previously been found closely adjacent to pulmonary venules in several diseases associated with alveolar hypoxia or pulmonary oedema including mitral stenosis, plexogenic pulmonary arteriopathy, pulmonary thromboembolism, and chronic obstructive pulmonary disease. METHODS Histological sections of the lungs of seven adult native highlanders from La Paz (3600 m) were examined. RESULTS Arachnoid nodules were found in the lungs of one Aymara and one Mestizo Indian. CONCLUSIONS These bodies may have a similar function to that of arachnoid granulations which transfer excess cerebrospinal fluid to the dural venous sinuses. In the native highlanders it is possible that they contribute to the avoidance of excessive hydration of the interstitial tissue of the alveolar walls with return of fluid into the pulmonary venules, preventing incipient pulmonary oedema.