Valvular heart disease has numerous etiologies. These range from congenital malformations to infectious and degenerative diseases. Clinically, these result in significant problems, the management of which can necessitate valve replacement with prosthetic heart valves. A rare cause is the deposition of foreign material in the valvular tissues, and these include inborn errors of metabolism of the essential amino acids. Alkaptonuria, an autosomal recessive trait, can result in the accumulation of excess homogentisic acid. This can manifest as pigmentation in the skin and other tissues, including heart valves. Accumulation of this pigment can lead to an inflammatory reaction and to progressive valve dysfunction.