Some Hunter syndrome patients suffer from neuronopathic involvement, due to the damage of nerve tissues by GAG accumulations, in which dermatan sulfate and heparan sulfate cause connective tissue damage and central nervous system (CNS) damage, respectively. 1 A variety of neuronopathic symptoms can manifest from this damage and regular assessments are important as the disease progresses and the symptoms become more advanced, debilitating and multisystemic. 2


When we have a situation when dermatan sulfate and heparan sulfate are stored together we will have […] MPS II […] with ‘neuronopathic’ sub-phenotype.

- Professor Anna Tylki-Szymańska


Behavioural problems and cognitive impairment are early features in Hunter syndrome patients with neuronopathic disease, and may be assessed using age-appropriate neurobehavioural/cognitive instruments. 2 Behavioural problems can be serious in Hunter syndrome patients, including hyperactivity, obstinacy and aggression, although these will eventually dissipate as cognitive function declines, at around the age of 8 or 9 years, and developmental regression occurs. The results of neurodevelopmental testing should be used to update the family and caregivers on the functional age of the patient. 2

Along with neurobehavioural issues, Hunter syndrome patients may suffer from a variety of other neuronopathic problems that should be assessed and carefully managed by the neurologist, including seizures, carpal tunnel syndrome and communicating hydrocephalus. 2

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  1. Węgrzyn G et al. Why are behaviors of children suffering from various neuronopathic types of mucopolysaccharidoses different? Med Hypotheses 2010; 75(6): 605–609.
  2. Muenzer J et al. Multidisciplinary management of Hunter syndrome. Pediatrics 2009; 124(6): e1228–e1239.