question: Q:A 2-year-old boy is brought to his pediatrician for evaluation of a tender red big toe. His mother also notes that she has seen him recently starting to bite his own fingers and also exhibits spasms of muscle tightness. She reports that his diapers often contain the substance shown in the photograph. On exam he is noted to be significantly developmentally delayed as he is neither walking nor talking. Which of the following would be the first-line pharmacologic treatment for this patient's disorder?? 
  {'A': '6-mercaptopurine', 'B': 'Allopurinol', 'C': 'Hydroxyurea', 'D': 'Methionine', 'E': 'Probenecid'},