A 52-year-old alcoholic notices a skin rash on his chest, and also has symptoms of diarrhea and abdominal pain. On examination, he has a scaly and pigmented rash on the sun-exposed areas of his skin, the abdomen is soft, and his short-term memory is impaired. He has dermatitis, diarrhea, and dementia syndrome.For the patient with vitamin deficiency or excess, select the most likely diagnosis
niacin thiamine pyridoxine vitamin C