Pellagra vs Scurvy
How to tell Pellagra and Scurvy apart when a board question makes them look alike.
Pellagra is dermatitis-diarrhea-dementia; scurvy is defective collagen with bleeding gums, corkscrew hairs, and poor wound healing.
Side by side
Pellagra is niacin deficiency causing photosensitive dermatitis, diarrhea, dementia, and can occur with Hartnup disease, carcinoid syndrome, or isoniazid use.
Scurvy is vitamin C deficiency causing poor wound healing, bleeding gums, perifollicular hemorrhage, corkscrew hairs, anemia, and impaired collagen hydroxylation.
Niacin deficiency reduces NAD/NADP-dependent redox reactions and can follow tryptophan diversion away from niacin synthesis.
Vitamin C deficiency prevents hydroxylation of proline and lysine residues, weakening collagen triple helix stability.
Dermatitis on sun-exposed skin, diarrhea, dementia, and low niacin support pellagra.
Bleeding gums, petechiae, corkscrew hairs, and poor wound healing support scurvy.
The trap
Both can show rash or weakness, but GI/dementia points niacin while bleeding collagen failure points vitamin C.
The repair move
For vitamin rash questions, decide whether the dominant problem is NAD deficiency or collagen hydroxylation failure.
Try a free question
CoreA 58-year-old man with chronic alcohol use and a corn-based diet has a hyperpigmented scaling dermatitis on sun-exposed surfaces of his neck (Casal necklace) and forearms, chronic watery diarrhea, and progressive memory loss and confusion. Which vitamin deficiency is most likely?
Show answer and explanation
Answer: A. Niacin (B3) deficiency causing pellagra. Pellagra is niacin deficiency with the three Ds (dermatitis, diarrhea, dementia). Corn-based diets, alcoholism, Hartnup disease (impaired tryptophan absorption), and carcinoid syndrome (tryptophan shunted to serotonin) can all precipitate it.
Why the other choices are tempting
- B. Scurvy presents with bleeding gums, perifollicular hemorrhages, corkscrew hairs, and poor wound healing, not photosensitive dermatitis with the 3 Ds.
- C. Riboflavin deficiency causes cheilosis, angular stomatitis, glossitis, and corneal vascularization.
- D. Pyridoxine deficiency causes sideroblastic anemia and peripheral neuropathy.
- E. Folate deficiency causes megaloblastic anemia, not the 3 Ds.
Flashcards
Tap a card to flip it.
What clue supports Pellagra?
Choose Pellagra when the stem gives this pattern: Pellagra is niacin deficiency causing photosensitive dermatitis, diarrhea, dementia, and can occur with Hartnup disease, carcinoid syndrome, or isoniazid use.
What clue supports Scurvy?
Choose Scurvy when the stem gives this contrasting pattern: Scurvy is vitamin C deficiency causing poor wound healing, bleeding gums, perifollicular hemorrhage, corkscrew hairs, anemia, and impaired collagen hydroxylation.
Quick answers
What is the fastest way to tell Pellagra from Scurvy?
Pellagra is dermatitis-diarrhea-dementia; scurvy is defective collagen with bleeding gums, corkscrew hairs, and poor wound healing.
What is the key clue for Pellagra?
Pellagra is niacin deficiency causing photosensitive dermatitis, diarrhea, dementia, and can occur with Hartnup disease, carcinoid syndrome, or isoniazid use.
What is the key clue for Scurvy?
Scurvy is vitamin C deficiency causing poor wound healing, bleeding gums, perifollicular hemorrhage, corkscrew hairs, anemia, and impaired collagen hydroxylation.
What is the common trap with Pellagra vs Scurvy?
Both can show rash or weakness, but GI/dementia points niacin while bleeding collagen failure points vitamin C.