Nail disorders causes different nail signs, the knowledge of which is mandatory for a correct diagnosis and the choice of appropriate treatment. The clinical signs depend on the portion of the nail apparatus that has been damaged: nail plate alterations are due to matrix damage, and nail detachment and uplifting are due to hyponychium or nail bed problems. Paronychia describes the inflammation of the proximal nail fold, which can lead to secondary matrix damage. The nail plate can be thinner or thicker than normal and have altered shape or dimensions. The nail can also show pigmentary changes, ranging from white to black, with various distributions: each of them can be a sign of different disease. The diagnosis may also rely on the associations of the different signs.