Ans. is 'c' i.e., Niacino Deficiency of niacin (and tryptophan) causes pellagra which is characterized by 3 Ds, i.e. dermatitis, diarrhea and dementia. Hartnup disease can cause pellagra in which there is a defect in membrane transport of tryptophan. Carcinoid syndrome can also cause pellagra as most of the tryptophan is used in the synthesis of serotonin (5- hydroxytryptamine).o Pellagra is common in people consuming maize and sorghum (jowar) as their staple foods. These two are poor in niacin and tryptophan, and rich in leucin. Excess of leucine inhibits the conversion of tryptophan into niacin.