Clinical and Molecular Features of Late Onset Huntington Disease in a Peruvian Cohort

Background: Late onset cases of Huntington disease (HD), with onset >= 60 years, account for up to 20% of HD cases worldwide. Clinical features include mild motor dysfunction with slow progression and cognitive impairment, frequent absence of family history and low number of CAG repeats. The clinical and molecular features of late onset HD is still understudied in Latin America. Objectives: To describe the clinical and molecular characteristics of late onset HD in a Peruvian cohort. Methods: An observational study was carried out by reviewing the HD registry at the Neurogenetics Research Center-INCN from 2000 to 2014. Genotyping of HTT gene was confirmed using standard PCR and PAGE in accordance to protocols previously established. Results: Thirty-one late onset HD cases from 27 pedigrees were identified (9.42% of total HD cases, n = 329), 51.61% were male. Mean age at onset was 64.1 +/- 4.2 and CAG repeats mean was 42.5 +/- 2.5. We did not find significant correlation between age at onset and CAG repeats. 33.3% of cases were traced back to Canete valley. Twenty-two cases had a positive family history, 14 of them with paternal transmission. Choreic movements and cognitive impairment were the main existing manifestations reported in this cohort, with lower frequency of psychiatric disturbances. Conclusions: This report of late onset HD affected individuals shows a mild phenotype expression of the disease, associated with low range of CAG repeats and up to 30 % of cases with absence of clear family history. Canete valley remains the region with more cases.