I AM A LOOKING TO GO

What’s causing this teenager’s vision loss?

Figure 1 Quiz of the Week A 14-year-old boy is brought to the pediatrician by his mother over concerns of difficulty walking and worsening clumsiness. He reports a gradual loss of night vision, and a long history of chronic diarrhea which is pale and foul-smelling. Examination reveals an ataxic gait, and loss of deep tendon…