Formation of pannus on prosthetic valves in a child with pseudoxanthoma elasticum.

A child with pseudoxanthoma elasticum had mitral valvar prolapse with severe regurgitation necessitating replacement with a prosthetic valve. Extensive formation of pannus caused obstruction of two mechanical valves, one after twenty months and the second after three years. Histology of the pannus was similar to the endocardial lesions that are considered unique to pseudoxanthoma elasticum.