A 6-Year-Old Boy Is Evaluated in the Office for Difficulty

A 6-year-old boy is evaluated in the office for difficulty hearing.  The patient has no ear pain, discharge, or upper respiratory symptoms.  Initial testing suggests that he has bilateral sensorineural hearing loss.  He has no motor deficits or cerebellar signs.  His paternal uncle died suddenly at age 12.  Examination of the ears, nose, and throat is normal.  ECG shows normal sinus rhythm with a prolonged QT interval (520 msec) .  Echocardiogram shows normal left and right ventricular function with no significant valvular disease.  A genetic defect affecting which of the following is most likely present in this patient?

A) Calcium channels
B) Membrane anchoring protein
C) Potassium channels
D) Sodium channels
E) Sodium-potassium ATPase

Correct Answer:

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