Behavioural phenotypes of the mucopolysaccharide disorders: a systematic literature review of cognitive, motor, social, linguistic and behavioural presentation in the MPS disorders

The mucopolysaccharide disorders (MPS) are a group of recessively inherited metabolic disorders resulting in progressive physical and cognitive decline. MEDLINE, PsycINFO and Embase databases were searched, alongside manual screening, to identify relevant literature. Papers were included in the review if they were published in a peer reviewed journal and conducted empirical research into cognitive, motor, social or linguistic development or behaviour in one or more MPS disorders. Twenty-five papers were reviewed. Two papers used methodology of a sufficiently high standard to demonstrate a behavioural phenotype; both found sleep disturbance to be part of the phenotype of MPS III. Fearfulness and sleep disturbance were frequently observed in people with MPS I and II. Cognitive and motor impairment and decline, and challenging behaviour were highly prevalent in the severe form of MPS II. Cognitive decline and severe behavioural problems relating to aggression, hyperactivity, orality, unusual affect and temper tantrums were seen in MPS III. Sleep disturbance is part of the behavioural phenotype of MPS III, and challenging behaviour is highly prevalent in MPS II and MPS III, therefore the efficacy of behavioural interventions for these populations should be investigated. Further research into the behaviour and adaptive skills of children with MPS III and MPS IV is required.