The hanup disease causes the deficiency of

Pellagra is caused by the deficiency of tryptophan and niacin. Pellagra is characterized by photosensitive dermatitis. As the condition progresses, there is dementia and possibly diarrhea. Untreated pellagra is fatal. Although the nutritional etiology of pellagra is well established, and either tryptophan or niacin prevents or cures the disease, additional factors, including deficiency of riboflavin or vitamin B6, both of which are required for synthesis of nicotinamide from tryptophan, may be impoant. A number of genetic diseases that result in defects of tryptophan metabolism are associated with the development of pellagra, despite an apparently adequate intake of both tryptophan and niacin. Hanup disease is a rare genetic condition in which there is a defect of the membrane transpo mechanism for tryptophan, resulting in large losses as a result of intestinal malabsorption and failure of renal reabsorption. In carcinoid syndrome, there is a metastasis of a primary liver tumor of enterochromaffin cells, which synthesize 5-hydroxytryptamine. Overproduction of 5-hydroxytryptamine may account for as much as 60% of the body's tryptophan metabolism, causing pellagra because of the diversion away from NAD synthesis. Reference: Harper; 30th edition; Page no: 557