You Are Examining a 5-Year-Old Male Child Who Has Been

You are examining a 5-year-old male child who has been exhibiting a tendency to bite his lower lip to the point of bleeding as well as chewing on his fingertips. Physical examination demonstrates swollen tender joints, and blood workup indicates elevated uric acid levels. These symptoms and lab results are indicative of a deficiency in which of the following enzymes?

A) adenosine deaminase
B) adenosine phosphoribosyltransferase
C) AMP deaminase
D) hypoxanthine-guanine phosphoribosyltransferase
E) thymidylate synthase