melanosis

noun
mel·​a·​no·​sis | \ ˌmel-ə-ˈnō-səs How to pronounce melanosis (audio) \
plural melanoses\ -​ˈnō-​ˌsēz How to pronounce melanoses (audio) \

Medical Definition of melanosis

: a condition characterized by abnormal deposition of melanins or sometimes other pigments in the tissues of the body