The nails are horny parts of the skin. Are organs exposed to the environment and because of this, often have problems caused sometimes by infections (fungi, bacteria, viruses), sometimes by other systemic or skin diseases (psoriasis, lichen planus, eczema, anemia, chronic lung disease, etc.) and other times by injuries or chronic use of drugs or cosmetic products (nail polish etc).
Common cause also are nutritional disorders and lack of vitamins, minerals and amino acids. The images show abnormal nails are too many and are related to the structure, shape and color of the nail. Thus, we can find nail aplasia, atrophy, hypertrophy, pachyonychia, onychogryposi (thick, curved, hard nails) koilonychia, lateral and longitudinal grooves, pits, hangnail, onychocryptosis (entrance of the lateral edge of the nail to the skin of the fingers by causing injury and inflammation usually in the big toes).