A 28-year-old man is evaluated for abnormal movements of the hands and face. The patient reports that he started experiencing involuntary grimacing a year ago, which has gradually worsened. He is taking a selective serotonin reuptake inhibitor for major depression but has not taken any antipsychotic medications. His 52-year-old father was diagnosed with an inherited movement disorder 2 months ago. Physical examination shows normal strength and normal deep tendon reflexes. No sensory deficits are noted. Which of the following best explains the difference in disease presentation between this patient and his father?

Question

A 28-year-old man is evaluated for abnormal movements of the hands and face.  The patient reports that he started experiencing involuntary grimacing a year ago, which has gradually worsened.  He is taking a selective serotonin reuptake inhibitor for major depression but has not taken any antipsychotic medications.  His 52-year-old father was diagnosed with an inherited movement disorder 2 months ago.  Physical examination shows normal strength and normal deep tendon reflexes.  No sensory deficits are noted.  Which of the following best explains the difference in disease presentation between this patient and his father?

Quizplus · Accepted Answer

Eductional Objective: An increased number of trinucleotide repeats on the HTT gene is associated with Huntington disease.  The larger the number of repeats, the earlier the onset of the disease.  Trinucleotide expansion occurs more frequently during paternal transmission, causing a genetic phenomenon called anticipation.

A 28-Year-Old Man Is Evaluated for Abnormal Movements of the Hands