Reader response: Clinical manifestations of homozygote allele carriers in Huntington disease.

We read with interest the article by Cubo et al.1 Patients with homozygous Huntington disease (HD) are rare—considering a patient as homozygous when presenting with repetitions greater than 36 in both alleles. Differences in age at onset, clinical characteristics, and evolution have been hypothesized because the gain function of the mutation is due to both alleles. Nevertheless, it has been shown that these patients have a similar clinical evolution. However, a very early study conducted by Squitieri et al.2 reported a more severe and rapid progression in homozygotes.