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- A more than normal amount of thick mucus made by the cells lining the upper airways and lungs. A buildup of phlegm may be caused by infection, irritation, or chronic lung disease, and can cause discomfort in the chest and coughing.
National Cancer Institute - Cite This Source - This Definition
- Asbestos, asbestosis, chronic obstructive pulmonary disease, COPD, emphysema, keloid, pneumonia