This paper reports a study of the nature and prevalence of behaviour p
roblems in 258 children with mucopolysaccharide disorders. Questionnai
re data obtained through the post was supplemented by home visits to 4
2 families in the sample and by regular discussions with families at m
eetings of the Society for Mucopolysaccharide Diseases. High rates of
behaviour problems were found, particularly in children with Sanfilipp
o's and Hunter's disease aged 5 to 9 years. These included destructive
ness, restlessness, and aggressiveness. Sleep problems were common acr
oss subtypes with an overall prevalence of 66%. Parents reported that
they received little or no support in the management of these difficul
t behaviours. It is concluded that behaviour problems are a primary fe
ature of the mucopolysaccharide disorders and place a major strain on
families. Services to help families cope with these problems are urgen
tly needed.