Rare inborn errors of metabolism with movement disorders: a case study to evaluate the impact upon quality of life and adaptive functioning

BACKGROUND Inborn errors of metabolism (IEM) form an important cause of movement disorders in children. The impact of metabolic diseases and concordant movement disorders upon children's health-related quality of life (HRQOL) and its physical and psychosocial domains of functioning has never been investigated. We therefore conducted a case study on the HRQOL and development of adaptive functioning in children with an IEM and a movement disorder. METHODS Children with co-existent IEM and movement disorders were recruited from paediatric outpatient clinics. We systematically collected clinical data and videotaped examinations. The movement disorders were diagnosed by a panel of specialists. The Pediatric Quality of Life Inventory 4.0 and the Vineland Adaptive Behavior Scale were used to assess the HRQOL and adaptive functioning, respectively. RESULTS We recruited 24 children (10 boys, mean age 7y 5 m). Six types of movement disorders were recognised by the expert panel, most frequently dystonia (16/24), myoclonus (7/24) and ataxia (6/24). Mean HRQOL (49.63, SD 21.78) was significantly lower than for other chronic disorders in childhood (e.g. malignancy, diabetes mellitus, rheumatic disease, psychiatric disorders; p <0.001) and tended to diminish with the severity of the movement disorder. The majority of participants had delayed adaptive functioning, most evident in their activities of daily living (51.92%, SD 27.34). Delay in adaptive functioning had a significant impact upon HRQOL (p = 0.018). CONCLUSIONS A broad spectrum of movement disorders was seen in patients with IEM, although only five were receiving treatment. The overall HRQOL in this population is significantly reduced. Delay in adaptive functioning, most frequently seen in relation to activities of daily living, and the severity of the movement disorder contribute to this lower HRQOL. We plead for a greater awareness of movement disorders and that specialists should be asked to diagnose and treat these wherever possible.