Abstract
PACS1 Syndrome is an ultra-rare neurodevelopmental disorder characterized by intellectual disability, behavioral disturbances, and multisystem involvement. While clinical knowledge is growing, its impact on quality of life (QoL) has not been systematically evaluated, and it is critical to understand the lived experience and psychosocial well-being of these individuals beyond strictly medical outcomes. This study aimed to assess QoL in individuals aged 4-21 years with PACS1 Syndrome using the validated KidsLife scale, proxy-reported by primary caregivers, given the intellectual disabilities and communicative limitations of this population. Twenty-one participants from Spain and other countries were recruited through the Spanish PACS1 Association, and 39 questionnaires from mothers and fathers were analyzed. The KidsLife scale provides standardized scores across eight QoL domains and a global QoL index (QoLI). The mean QoLI was 48.1 ± 28.3, slightly below the median for individuals with intellectual disability, but higher than other neurodevelopmental disorders such as Cornelia de Lange Syndrome. The findings revealed a pattern: while domains related to social inclusion, rights, and physical and material well-being were relatively preserved, reflecting adequate care and access to resources, the most significant compromises were observed in autonomy-related domains, specifically self-determination, interpersonal relationships, and personal development. Most individuals showed a high degree of dependency, and those with greater dependency exhibited lower QoL scores. This situation led more than half of families to reduce their working hours, with caregiving responsibilities disproportionately falling on mothers. Although no statistically significant differences were found between parental ratings, mothers tended to report higher QoL. These findings reflect the substantial functional impact of PACS1 Syndrome and emphasize the need for multidisciplinary support to improve autonomy, social participation, and overall well-being.