A 10-day-old boy is brought to the emergency department for evaluation of
generalized tonic-clonic seizures. The parents note recurrent upper and lower extremity
muscle spasms. He has had no fever, cough, or runny nose. The patient was born full term via an uncomplicated pregnancy and normal
vaginal delivery. Family history is unremarkable. Physical examination demonstrates a neonate with rhythmic jerking movements of the upper and lower of extremities bilaterally. The anterior fontanelle is open,
pupils are reactive to light, and fundi are normal. Facial examination reveals a small lower jaw, low set
ears, and a submucosal
cleft palate. Lungs are clear to
auscultation bilaterally.
Cardiac auscultation reveals a harsh holosystolic
murmur at the left lower
sternal border.
Chest x-ray demonstrates decreased
soft tissue attenuation in the right
anterior mediastinum. Which of the following immunologic derrangements is most likely to be observed in this patient?
