Which classic vitamin deficiency is known for the four Ds: dermatitis, dementia, diarrhea, and death?

• A. Thiamine
• B. Biotin
• C. Folic acid
• D. Niacin

Answer: (D)

Pellagra, caused by a deficiency of niacin (vitamin B3), is defined by the four Ds: dermatitis, dementia, diarrhea, and, if untreated, death. Niacin is needed to form the coenzymes NAD+ and NADP+, which drive many energy-producing reactions in cells; without enough niacin, tissues—especially skin, brain, and gut—manifest the characteristic symptoms. Niacin can be consumed directly or produced from tryptophan, so factors that limit dietary niacin or tryptophan availability raise risk, such as maize-based diets with poor niacin bioavailability, chronic alcoholism, malabsorption, or conditions like Hartnup disease. The other options correspond to different vitamin deficiencies: thiamine deficiency leads to beriberi and Wernicke-Korsakoff syndrome, biotin deficiency causes dermatitis with alopecia and enteritis, and folic acid deficiency causes megaloblastic anemia and, in pregnancy, neural tube defects. Recognizing the four Ds points to niacin deficiency and pellagra, guiding appropriate treatment and addressing underlying causes.