paronychia A nail disease characterized by often-tender bacterial or fungal hand infection or foot infection due to either bacteria or fungus (Candida albicans) where the nail and skin meet at the side or the base of a finger or toe nail. The infection can start suddenly (acute paronychia) or gradually (chronic paronychia). Puss is usually present, along with gradual thickening and browning discoloration of the nail plate. nail disease