A case of a quadricuspid pulmonary valve in a Japanese female.

A supernumerary cusp of the pulmonary valve was incidentally found in an 88-year-old Japanese female during a gross anatomy course. The valve was composed of three equal-sized leaflets and one smaller leaflet. The supernumerary leaflet was located between the anterior and right semilunar leaflets. This pulmonary valve consisted of four pulmonary aortic bulbs. The donated body was a female who had a past history of myocardial infarction and was diagnosed as having ischemic heart disease at the last admission. Tricuspid valve regurgitation and pulmonary hypertension were diagnosed on echocardiography. These findings were considered to have been caused by left heart failure and not by the quadricuspid pulmonary valve. This asymptomatic anatomical variation might have developed from a protrusion between the anterior and right swelling of the outflow tract during semilunar valve development.