Riboflavin
Riboflavin is involved in carbohydrate metabolism as an essential coenzyme in many oxidation-reduction reactions involved in carbohydrate and protein metabolism (see table Sources, Functions, and Effects of Vitamins). Riboflavin is essentially nontoxic.
Dietary sources include milk, cheese, liver, meat, eggs, and enriched cereal products. (See also Overview of Vitamins.)
Etiology of Riboflavin Deficiency
Primary riboflavin deficiency results from inadequate intake of the following:
Fortified cereals
Milk
Other animal products
Secondary riboflavin deficiency is most commonly caused by the following:
Chronic diarrhea
Liver disorders
Long-term use of barbiturates
Chronic alcohol use disorder
Symptoms and Signs of Riboflavin Deficiency
The most common signs of riboflavin deficiency are pallor and maceration of the mucosa at the angles of the mouth (angular cheilitis) and vermilion surfaces of the lips (cheilosis), eventually replaced by superficial linear fissures. The fissures can become infected with Candida albicans, causing grayish white lesions (perlèche). The tongue may appear magenta.
Seborrheic dermatitis develops, usually affecting the nasolabial folds, ears, eyelids, and scrotum or labia majora. These areas become red, scaly, and greasy.
Rarely, neovascularization and keratitis of the cornea occur, causing lacrimation and photophobia.
Diagnosis of Riboflavin Deficiency
Therapeutic trial
Urinary excretion of riboflavin
The lesions characteristic of riboflavin deficiency are nonspecific. Riboflavin deficiency should be suspected if characteristic signs develop in a patient with other B vitamin deficiencies.
Diagnosis of riboflavin deficiency can be confirmed by a therapeutic trial or laboratory testing, usually by measuring urinary excretion of riboflavin.
Treatment of Riboflavin Deficiency
Supplemental riboflavin and other water-soluble vitamins
Sometimes riboflavin given by parenterally
Sometimes riboflavin is given parenterally as one vitamin in a multivitamin preparation.
Key Points
Riboflavin deficiency causes various nonspecific skin and mucosal lesions, including maceration of mucosa at the angles of the mouth (angular cheilitis) and surfaces of the lips (cheilosis).
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