▁sign alling ▁protein ▁can ▁permit ▁un medi ated ▁e um el an in ▁production , ▁producing ▁a ▁uniformly ▁black - to - b rown ▁coat ▁color . ▁This ▁condition ▁can ▁be ▁observed ▁in ▁dogs , ▁c ats , ▁and ▁horses . ▁The ▁appearance ▁of ▁m amm als ▁with ▁re cess ive ▁ag out i ▁mut ations ▁is ▁typically ▁dense ▁black . ▁As ▁with ▁a e um el an ism , ▁the ▁difference ▁between ▁lack ▁of ▁ph ae om el an in ▁and ▁abund ance ▁of ▁e um el an in ▁is ▁one ▁of ▁words . ▁Some ▁ag out i ▁alle les ▁in ▁m ice ▁are ▁associated ▁with ▁health ▁defect s , ▁but ▁this ▁is ▁not ▁the ▁case ▁in ▁dogs , ▁c ats , ▁or ▁horses . ▁ ▁See ▁also ▁Al bin ism ▁Dy sch rom ia ▁E ry th r ism ▁H eter och rom ia ▁ir id um ▁Le uc ism ▁Mel an ism ▁P ieb ald ism ▁Vit il igo ▁X anth och rom ism ▁ ▁References ▁▁ ▁Category : Dist urban ces ▁of ▁p ig ment ation ▁Category : Gen etic ▁dis orders ▁with ▁no ▁O M IM ▁Category : D erm at olog ic ▁termin ology <0x0A> </s> ▁Digital ▁Item ▁is ▁the ▁basic ▁unit ▁of ▁transaction ▁in ▁the ▁M PE G - 2 1 ▁framework . ▁It ▁is ▁a ▁struct ured ▁digital ▁object , ▁including ▁a ▁standard ▁representation , ▁identification ▁and ▁metadata . ▁▁ ▁A ▁Digital ▁Item ▁may ▁be ▁a ▁combination ▁of ▁resources ▁like ▁videos , ▁audio ▁tracks ▁or