Clinical and genetic features of Huntington disease in Sri Lanka

Huntington disease was one of the first neurological hereditary diseases for which genetic testing was made possible as early as 1993. The study describes the clinical and genetic characteristics of patients with Huntington disease in Sri Lanka.

Data of 35 consecutive patients tested from 2007 to 2012 at the Human Genetics Unit, Faculty of Medicine, University of Colombo was analyzed retrospectively. Clinical data and genetic diagnostic results were reviewed. Statistical analysis was performed using descriptive statistics.

Thirty patients had fully penetrant (FP) CAG repeat mutations and 5 had reduced penetrant (RP) CAG repeat mutations. In the FP group mean ages of onset and diagnosis were 37.5 and 40.4 years, while in the RP group it was 63.0 and 64.8 years respectively. The age of diagnosis ranged from 15 to 72 years, with 2 patients with Juvenile onset (<20 years) and 3 with late onset (>60 years) Huntington disease. The symptoms at diagnosis were predominantly motor (32/35 -91%). Three patients had psychiatric and behavioral disorders. The age difference between onset and genetic diagnosis showed significant delay in females compared to males (p < 0.05). Twenty two (62.8%) had a positive family history, with 13/22 (59.1%) showing a paternal inheritance of the disease. In both groups, those with a family history had a significantly lower age of presentation (p < 0.05). The mean CAG repeat length in patients with FP alleles was 44.6 ± 5 and RP alleles was 37.2 ± 1.1. Age of onset and CAG repeat length of the HTT gene showed significant inverse correlation (p < 0.0005, R2 = 0.727).

The clinical and genetic features seen in patients with Huntington disease in the Sri Lankan study population were similar to that previously reported in literature.