[The development of cognitive functions in children with Hurler phenotype mucopolysaccharidosis type I on enzyme replacement therapy with laronidase]

Abstract

Introduction: Mucopolysaccharidosis type I (MPS I) Hurler syndrome, Hurler/Scheie i Scheie is a metabolic disorder manifesting in early childhood, and characterized by the accumulation of mucopolysaccharides (glycosaminoglycans - GAG) in the cells, blood, and connective tissues. Eventually, this causes damage to cells and organs, leading to progressive impairment of the child's physical abilities, organ function, and mental development. Treatment with enzyme replacement therapy (ERT) alleviates many symptoms of the disease, however, there is no evidence indicating that ERT is effective in the prevention of nervous system degradation.

The aim of the study: The current study seeks to assess the development of cognitive functions in ERT-treated children with Hurler syndrome.

Material and methods: The analysis covers 8 children suffering from MPS type I (7 boys and 1 girl), aged from 9.8 months to 12.7 months at the beginning of the study. All were on enzymatic treatment for the first year of life. The level of intellectual development was measured using the Psyche Cattell Infant's Intelligence Scale.

Results: Children with MPS type I achieved significantly lower IQ scores compared to the reference group of healthy children. Qualitative analyses revealed that the acquisition of skills and new cognitive functions is very slow in children with MPS type I.

Conclusions: 1. Among children with MPS type I, there was a measurable decrease in IQ associated with advancing age. 2. In spite of lower IQ, the acquisition of new abilities does occur, but the pace of that development is slower than that expected for the child's age. 3. The study reveals the need for functional diagnosis of development, in order to assess the progress made by the child.