Vitamins are an indispensable food source and important owing to the enzyme cofactor and catalytic roles they play in the body. Fat-soluble vitamins A, D, E, K, and B12, are stored in the body and can cause problems with their excessive accumulation. Other vitamins rarely accumulate in the body because they dissolve in water and are excreted through the kidneys. Alcoholism, strict diets, insufficient parental nutrition, and gastrointestinal absorption problems may be included in the causes of vitamin deficiencies. Although clinical findings of vitamin deficiencies display different characteristics depend-ing on the vitamins, the signs that generally occur are cutaneous pigmentation, pigmentation on mucous membranes, palmoplantar keratoderma characterized by fissures, palmar streaking, yellow streaking on the nails, nail layering, and intranail hemorrhage. (c) 2021 Elsevier Inc. All rights reserved.