The relationship between (CAG)n repeat number and age of onset in a family with dentatorubral-pallidoluysian atrophy (DRPLA): diagnostic implications of confirmatory and predictive testing.

Dentatorubral-pallidoluysian atrophy (DRPLA) is a rare neurodegenerative disorder characterised by variability in both age of onset and clinical features. Despite the recent identification of the CAG expansion mutation in DRPLA, the number of molecularly confirmed cases remains small. Given its rarity and prominent phenotypic heterogeneity, some care needs to be exercised in the interpretation and dissemination of test results derived from direct gene testing for the DRPLA specific expansion mutation.