Pulmonary valve stenosis is most often caused by a malformation during fetal development. The cause is unknown. A narrowing may occur in the pulmonary valve or below the pulmonary valve at the pulmonary artery. The defect may occur alone, but is relatively common in connection with other heart defects. The condition can be mild or severe. It occurs in approximately 10% of patients with congenital heart disease. Pulmonary stenosis can also occur later in life as a result of conditions that cause damage or scarring of the heart valves. These include rheumatic fever, endocarditis, and other disorders.
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