Snapshot A 12-year-old boy is brought to his pediatrician by his mother due to progressive confusion, diarrhea, and an itchy rash. He recovered from the flu about a week ago but was still feeling tired. Over the last 48 hours, he has had several episodes of diarrhea per day. On exam, he has a tremor, intermittent ataxia, and a rash (shown in the photograph). His mom says that he has previously had these kinds of symptoms usually after he has an illness. He is given nicotinic acid and placed on a high protein diet and quickly recovers. Introduction Amino acid clearance login to view 10 more bullets Hartnup deficiency login to view 10 more bullets Presentation Symptoms login to view 6 more bullets Physical exam login to view 3 more bullets Studies Serologies login to view 1 more bullet Labs login to view 1 more bullet Differential Pellagra due to vitamin deficiency Malignant carcinoid syndrome Treatment Conservative login to view 11 more bullets Complications Complications login to view 1 more bullet