Natural history of neuronopathic form of Hunter syndrome in children: observational cohort study

Introduction. Mucopolysaccharidosis type II (MPS II, Hunter syndrome) (mucopolysaccharidosis type II, MPS II) is a progressive multisystem disorder. Neurodegenerative course characterizes the severe (neuronopathic) form of MPS II. Pathogenetic therapy for the severe form of the disease is under development, and symptomatic neurological treatment is to be improved. Natural history data are required for rationalization of symptomatic care and assessment of emergent treatment effectiveness. The aim of the study. To describe the course of neurodegenerative disease in children with neuronopathic form of MPS II. Materials and methods. Fifty eight boys with established diagnosis of MPS II were included in the study. The course of the disease in 42 patients was classified as neuronopathic. Data on complaints, anamnesis and neurological examination obtained from medical documentation and within the framework of this study, as well as descriptions of video-EEG monitorings, performed in National Medical Research Center of Children’s Health, were used. Results. The spectrum and chronology of neurological symptoms in children with severe Hunter syndrome were described. 64% of patients were found to achieve the level of phrasal speech at any time of the development. Laughter or crying paroxysms in children with neuronopathiс MPS II were judged to be a manifestation of pseudobulbar affect. Burden of sleep disorder was demonstrated to increase through the course of the disease. Absence of epileptic seizure was significantly more frequent than epilepsy manifestation during the first two years after epiactivity appears on EEG (75 vs 25%; p = 0.046). Conclusion. Obtained natural history descriptions of severe MPS II cases are intended to be used in optimization of neurological care for patients and in assessment of emergent treatments’ effectiveness in real clinical practice.