Vegetations on under surface of cusps are found in:
Infective endocarditis
Libman sacks endocaditis
SABE
Rheumatic fever
Vegetations in Libmann sacks endocarditis occur on surfaces of cusps.Both surfaces may be involved but more commonly the undersurface is affected .(ref Robbins 7th/597,89,9/e p558)
Cardiovascular system