A 4-Month-Old Boy Is Brought to the Office Due to Abnormal

A 4-month-old boy is brought to the office due to abnormal twisting movements of the limbs and torso.  The patient also is not able to push up on his arms when prone.  He was born at full term to a 30-year-old woman by forceps-assisted vaginal delivery.  The delivery was complicated by cephalohematoma.  The patient has not been evaluated since discharge at age 2 days.  Vital signs are normal.  Weight and length are at the 50th percentile for age.  His eyes are crossed, and he does not react to sound.  Dystonic extremities are noted on examination.  Which of the following is the most likely explanation for this patient's current condition?

A) Autoimmune injury to basal ganglia
B) Bilirubin-induced neurotoxicity
C) MECP2 gene mutation
D) Physiologic chorea of infancy
E) Trinucleotide repeat expansion on chromosome 4p