The exact cause of Erdheim-Chester disease (ECD) is unknown. However, the disease is thought to represent an abnormal inflammatory process characterized by excessive proliferation and accumulation of certain cells, with associated scarring or overgrowth of fibrous connective tissue (fibrosis).
humidity (relative and absolute) The amount of water vapor in the air. Humidity is measured in two ways: (1) Absolute humidity is the percentage of water vapor actually present in the air. (2) Relative humidity is the absolute humidity divided by the amount of water that could be present in the air. Relative humidity indicates the degree of comfort or discomfort one feels from the humidity, because it indicates the amount of perspiration that can evaporate from the skin.
Air is a mixture of gases, which includes nitrogen, oxygen, carbon dioxide and water vapor (water in its gas form). Humidity refers to the amount of water vapor in air. All air contains at least some water vapor, but the amount of water vapor changes a lot from place to place and from time to time.