All of the available answer options are genes that can have pathologic nucleotide repeats. C9ORF72, which is responsible for hereditary ALS, is the only hex-nucleotide repeat disorder listed, while the rest are trinucleotide repeat disorders.

This patient is presenting with bulbar complaints, lower motor neuron findings on exam, and gynecomastia. This combination of symptoms seen in males between the age of 30 and 50 is consistent with Kennedy’s disease, also known as Spinal and Bulbar Muscular Atrophy (SBMA). This syndrome is due to a pathologic number of CAG repeats on the androgen receptor (AR) gene located on the X chromosome. Since it is an X-linked syndrome, female carriers are often not affected.

Pathology to the FMR1 gene is responsible for fragile X syndrome. A 40+ CAG repeat of the Huntington gene can lead to full penetrance of Huntington’s disease. The frataxin gene is related to Friedreich’s ataxia