Demyelinating disorders Quiz: Ace Your Exams

A 14-year-old boy is brought to the clinic by his mother due to complaints of weakness and numbness in the lower extremities. The patient has sprained both ankles on multiple occasions over the past year while playing soccer due to difficulty running, which has progressively worsened. The patient has not had any recent infections or diarrhea. The patient's family lives in a new home built 3 years ago. The patient’s mother reports the patient was adopted at the age of 3, and she is unsure of his biological family’s history. Vital signs are within normal limits. Distal calf muscle atrophy is noted. There is loss of proprioception and vibratory sensation in both feet. Ankle reflexes are 1+ bilaterally. An image of the patient’s foot is shown below. This patient’s neurological dysfunction is most likely caused by which of the following?  



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