A 31-year-old woman requests genetic testing for Huntington disease. She has a close friend who recently had a positive genetic test result for the huntingtin gene mutation, and she would like to undergo testing for assurance that she is without the disease. She is asymptomatic. Medical history is unremarkable. She takes no medications. On physical examination, vital signs are normal. Neurologic examination and the remainder of the examination are normal. Which of the following is the most appropriate management?
A. Obtain a brain MRI
B. Obtain a three-generation family history
C. Obtain genetic testing
D. Refer for genetic counseling