Pellagra is common in countries where corn or millet are staple foods. The cause is a nicotinic acid deficiency. Nicotinic acid amide is found in most foods, but the intake of the cereals mentioned is insufficient. Corn and millet have a high leucine content, which leads to a higher need for nicotinic acid. Corn also contains antimetabolites (structurally similar substances that interfere with the absorption and effectiveness of the vitamin). There are also secondary pellagra forms, the cause of which is absorption disorders (malabsorption).
The skin exposed to sunlight shows dermatitis (pellagrosis) with hyperpigmentation. If left untreated, it changes into strongly pigmented hyperkeratoses (thickening of the horny layer) and painful fissures (tears, "fissures"). In addition, there are diarrhea, polyneuropathies and anemia, and in extreme cases damage to the CNS.
Pellagra-like symptoms also occur in disorders of the tryptophan metabolism (Hartnup syndrome), as nicotinic acid is partially synthesized from tryptophan.
Therapy: oral (parenteral for absorption disorders) administration of nicotinic acid or nicotinic acid amide.