Background Unawareness of disease manifestations in neurodegenerative diseases has been defined by Flashman et al 2002 as “pathological unawareness of a neurological or functional deficit” and by Antoine et al 2004 as “the discrepancy between the patient's self report and the report of a natural caregiver or the clinical rating of a health professional”. Affected patients may have no complaints (symptoms) in contrast with a carer's or examiner's observations. Unawareness of movements and impairments in cognitive, emotional and functional capacity are documented in diagnosed Huntington Disease (HD). The PREDICT-HD study of mutation carriers allows a study of unawareness in the HD prodrome to phenoconversion.

Aims Determine if PREDICT-HD participants have motor complaints at the time motor phenoconversion and document differences between groups with and without awareness on cognitive, functional and behavioural measures.

Methods The PREDICT-HD database cross sectional information recorded at the third annual study visit for participants was reviewed. Demographics, motor, functional, cognitive and behavioural scores were analysed. Unawareness was identified as lack of agreement between participant report of symptoms and the trained examiner's rating of a diagnosis of unequivocal signs of HD. The groups with and without self-reported symptoms and an examiner rating of motor onset were compared on a range of cognitive, functional and behavioural measures, accounting for CAG repeat length and age.

Results Of 550 participants at the third annual PREDICT—HD visit, motor phenoconversion was recorded in 38 (6.91%). Of those, 18 (47.36 %) reported that they had no motor symptoms but were given a similar motor rating to those who reported having symptoms. The groups with and without reported motor symptoms but with signs were similar on measures of executive dysfunction and motor score. Phenoconverters without symptoms reported less depression.

Conclusions Poor awareness may occur in the prodromal stage and at phenoconversion to early HD or “HD onset”, as well as in later stages. Unawareness should be considered in assessment and provision of care.