What causes pleurisy?

Pleurisy is caused by infection, inhaled chemicals or toxic substances, collagen vascular diseases, cancers, tumors of the pleura (two membranes that cover the lungs and line chest wall), congestion, pulmonary embolism, obstruction of the lymph channels, trauma to the chest area, certain drugs (e.g. Hydralazine, Procan), abdominal processes, and lung infarction.