Trials in rare diseases: the need to think differently

Symptoms of Autism Spectrum Disorder (ASD) in Individuals with Mucopolysaccharide Disease Type III (Sanfilippo Syndrome): A Systematic Review

The prevalence of autism spectrum disorder (ASD) in many genetic disorders is well documented but not as yet in Mucopolysaccharidosis type III (MPS III). MPS III is a recessively inherited metabolic disorder and evidence suggests that symptoms of ASD present in MPS III. This systematic review examined the extant literature on the symptoms of ASD in MPS III and quality assessed a total of 16 studies. Results indicated that difficulties within speech, language and communication consistent with ASD were present in MPS III, whilst repetitive and restricted behaviours and interests were less widely reported. The presence of ASD-like symptoms can result in late diagnosis or misdiagnosis of MPS III and prevent opportunities for genetic counselling and the provision of treatments.

Demographic and Psychosocial Influences on Treatment Adherence for Children and Adolescents with PKU: A Systematic Review

Phenylketonuria (PKU) is a rare genetic disorder in which the amino acid phenylalanine cannot be sufficiently metabolised. Although a build-up of phenylalanine causes irreversible cognitive impairment, this can be prevented through a strict, lifelong diet restricted in natural protein. Despite the severe consequences of poor metabolic control, many children and adolescents have phenylalanine levels above their recommended limits. This systematic review was the first to examine studies reporting demographic and/or psychosocial influences on blood phenylalanine levels, with the aim to identify factors that were robustly linked with metabolic control. Four electronic databases were searched, yielding 1,808 articles. Articles were included if they reported a statistical examination of the association between one or more demographic or psychosocial factor(s) and metabolic control (as measured by blood phenylalanine concentration) for children and adolescents with PKU. Twenty-nine studies were selected for inclusion, which examined a range of child, parent and family factors related to blood phenylalanine levels. The most reproducible association was with child age, with metabolic control worsening with increasing age. This suggests that interventions promoting treatment adherence would be particularly beneficial for adolescents. There was a paucity of studies in some areas, and the quality of included studies varied; therefore, the conclusions of this review are preliminary. Research recommendations focus on promoting the growth of the evidence-base to support clinical practice.