Background Although the primary neuropathology of HD is that of neurodegeneration, mutant Huntingtin (mHTT), which is present throughout the life span, may also affect normal brain development. Therefore, subtle differences in behaviour, cognition, and motor skills may be present life-long (ie, functional “traits”) with significant worsening of these functions as disease onset approaches. The KidsHD program evaluates children (ages 6–18 years) who are at risk for HD (no children manifesting symptoms, no JHD included). For research purposes only, participants are genotyped and separated into gene-expanded (GE) and those that are non gene-expanded (GNE). A group of normal healthy control (HC) children are also assessed.

Aims To evaluate effects of gene-expansion on quantitative measures of behaviour in GE, GNE, and HC children.

Methods Parents completed ratings on two standardised questionnaires, Paediatric Behaviour Scale (PBS) and Behaviour Rating Inventory of Executive Function (BRIEF). GE children (n=29) and GNE children (n=30) were each matched by sex and age to three HC children. Multiple Analysis of Covariance (MANCOVA) was used to compare behaviour ratings across groups controlling for age sex and social class. The higher the scores, the more problematic the behaviour.

Results GE children had significantly elevated scores compared to HC: opposition, explosiveness, impulsivity, hyperactivity, and inattention within PBS. Depression/anxiety scores were not elevated. Within the BRIEF, the GE group had elevations in shifting, initiation, working memory, planning/organizing and monitoring scores. GNE had no significant differences in scores compared to HC.

Conclusions Subtle but significant differences in behaviour in children who are estimated to be decades ahead of HD diagnosis may reflect early influence of mHTT on normal neural developmental process, manifesting in specific patterns of behavioural traits.