Erythronychia is a term that covers a range of pathological patterns of red discoloration of the subungual tissues. The intensity of the red contrasts with the pale pink of the nail bed or the cream color of the lunula. It is typically due to one or more actors that include inflammation, vessel proliferation, and engorgement and focal thinning of the nail plate. This article describes the patterns both within an individual digit and when it extends to multiple digits. These patterns cover diverse inflammatory, infiltrative, and neoplastic diseases, and the correlation between these diagnoses and patterns is discussed alongside means of surgical diagnosis and cure.