system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
A 17-year-old high school student presents to your office for recent mood and skin changes. The patient is a high school senior who is competing on the wrestling team and recently has lost weight to drop two weight classes over the past several months. He states he has dry, cracking, and irritated skin, as well as a sensation of tingling in his hands and feet. The patient also states that he has not been feeling himself lately. He finds himself more irritable and no longer enjoys many of the activities he once enjoyed. He finds that he often feels fatigued and has trouble concentrating. The patient does not have a significant past medical history and is not on any current medications. The patient admits to drinking alcohol and smoking marijuana on special occasions. He states that he uses supplements that his other team members use. Physical exam is significant for acne, dry, cracked skin around the patient's mouth in particular, and decreased sensation in his lower extremities. Laboratory values are as follows:

Serum:
Na+: 137 mEq/L
Cl-: 101 mEq/L
K+: 4.1 mEq/L
HCO3-: 24 mEq/L
BUN: 15 mg/dL
Glucose: 79 mg/dL
Creatinine: 0.9 mg/dL
Ca2+: 9.2 mg/dL
Mg2+: 1.5 mEq/L
Homocysteine: 11.2 µmol/L (normal: 4.6 to 8.1 µmol/L)
AST: 11 U/L
ALT: 11 U/L
Alkaline phosphatase: 27 U/L
Albumin: 4.5 g/dL
Total protein: 6.9 g/dL
Total bilirubin: 0.5 mg/dL
Direct bilirubin: 0.3 mg/dL

Which of the following is the most likely diagnosis?
assistant
Water soluble vitamin deficiency