A 30-year-old man presents with a 1-week history of a painful tongue. He has also been having diarrhea, and he has been forgetting things more easily. He recently emigrated from India and lives alone on a maize-based diet. On examination, you note that the tip and margins of his tongue are a bright scarlet color. He also has a symmetrical erythematous rash on his forearms.
What is the most likely diagnosis?
A) Vitamin A deficiency
B) Pyridoxine deficiency
C) Vitamin C deficiency
D) Niacin deficiency
E) Vitamin E deficiency
