mayidism n : a disease caused by deficiency of niacin or tryptophan (or by a defect in the metabolic conversion of tryptophan to niacin); characterized by gastrointestinal disturbances and erythema and nervous or mental disorders; may be caused by malnutrition or alcoholism or other nutritional impairments [syn: {pellagra}, {Alpine scurvy}, {mal de la rosa}, {mal rosso}, {maidism}, {Saint Ignatius' itch}]