Nail dystrophy (Human Phenotype Ontology term HP_0008404) can be described as follows. Onychodystrophy (nail dystrophy) refers to nail changes apart from changes of the color (nail dyschromia) and involves partial or complete disruption of the various keratinous layers of the nail plate. Also known as: Dystrophic nails, Onychodystrophy, Poor nail formation.