Acral pigmentation in alkaptonuria resembling degenerative collagenous plaques of the hands: A report of five cases

To the Editor: Alkaptonuric ochronosis is a rare autosomal recessive metabolic disorder wherein deficiency of the enzyme homogentisic acid oxidase leads to deposition of pigment in various tissues. Polymerized homogentisic acid in the dermis imparts the characteristic blue-black discoloration responsible for “ochronosis.” Pigmentation of the sclera (Osler sign), pinnae, face and other sun-exposed areas is an established mucocutaneous marker for...