This patient should be referred for genetic counseling. Huntington disease, a neurodegenerative disorder, is transmitted as an autosomal dominant condition and is caused by cytosine-adenine-guanine trinucleotide repeat expansion in the HD gene (also known as the huntingtin or HTT gene). This patient has family members in multiple generations who have been diagnosed with Huntington disease, and he has a 50% chance of inheriting the gene from his father. Obtaining presymptomatic genetic testing in this patient would be appropriate; however, testing should only be performed after the patient undergoes genetic counseling. Key components of genetic counseling include informing the patient of the purpose of the test, implications of the test results, alternative testing options (including the option of foregoing testing), and possible risks and benefits of testing.

Although the choreiform movements that are seen in patients with symptomatic Huntington disease can be captured on electromyography, electromyography is not typically used in diagnosing Huntington disease and has no role in presymptomatic testing. Therefore, obtaining an electromyogram in this patient would not be appropriate.

Performing genetic testing without first providing adequate genetic counseling is not an appropriate intervention. It is essential that patients understand all of the ramifications of testing before testing is performed in order to make an educated decision.

It is inappropriate to tell this patient that genetic testing is unnecessary. Genetic testing is clearly warranted if the patient desires it.