Source : Webster's Revised Unabridged Dictionary (1913)

Uroerythrin \U`ro*e*ryth"rin\, n. [See 1st {Uro-}, and
   {Erythrin}.] (Physiol. Chem.)
   A reddish urinary pigment, considered as the substance which
   gives to the urine of rheumatism its characteristic color. It
   also causes the red color often seen in deposits of urates.