Mucopolysaccharidosis type III (Sanfilippo disease) in Sweden: clinical presentation of 22 children diagnosed during a 30-year period

Aim: The aim of this study was to present the natural clinical course in children and adolescents with MPS III diagnosed during a 30-year period in Sweden. Methods: The patients were identified from metabolic laboratory records between 1975 and 2004. Patient data were assessed from interviews of parents and by clinical examination and records from the patients. Results: A total of 15 children, 68%, with MPS IIIA were diagnosed at a median age of 6.8 years (range 1.2-18.9 years). One boy had MPS IIIB and five children MPS IIIC, diagnosed at ages between 1.9 and 11.6 years. In one child the type was not determined. The median age of children with type IIIA who had deceased was 16.2 years (range 10.4-31.2 years). Ten individuals with MPS III are alive at ages between 5 and 29 years. In four families, two children were affected. Conclusion: In 22 Swedish children with Sanfilippo disease an early normal development followed by a delay in speech and an appearance of behaviour problems was found in most children during the early preschool period. Mental retardation was diagnosed in almost all individuals before starting school. Early diagnosis is important in this devastating, progressive disorder, not only for genetic counselling but also for participation in future treatments.