Determining Phases of Disease Progression in Mucopolysaccharidoses Type IIIA: Analysis of Age Versus Neuropsychological Development
Mucopolysaccharidosis type III is a rare neurodegenerative disease caused by an enzyme deficiency required for the degradation of heparan sulfate. Of the four subtypes, A, B, C, and D, mucopolysaccharidosis type IIIA (MPS IIIA) has the most severe neurological consequences, resulting in severe dementia and death in the second decade of life. While the preponderance of research investigates the genetic mechanisms underlying the disease, fewer emerging studies explore the stages of neuropsychological deterioration that accompanies disease progression. The current study attempts to validate the three-stage model of MPS IIIA disease progression proposed by previous research by cross-sectionally comparing developmental ability across age groups of subjects with MPS IIIA. Using the Bayley Scale of Infant and Toddler Development, Edition III, investigators collected composite scores of cognition, language, and motor ability from thirty-one participants who have been previously diagnosed with MPS IIIA. Participants were assigned by age into one of the three stages of disease progression, defined by age cut-off set by existing literature (Valstar et al, 2008). Investigators witnessed that cognitive performance was the only domain that significantly varied between age-grouped phases, particularly declining ability with age. Discovering declining cognitive ability despite progressing age provides preliminary support of the three-stage model, illustrating that differences in developmental ability sorted by age are notable. Solidifying precise phases of disease progression of MPS IIIA will not only deepen the understanding of the disease but also maximize the effectiveness of future interventions due to the awareness of the sequence of deterioration.