Abstract
BackgroundThis article presents the results of long-term observations and comparative analysis of genotype–phenotype features in a large group of patients (227 males and one female) with a severe, intermediate and mild form of Hunter syndrome, evaluating the quality and span of their lives, as well as their ability to social adaptation.MethodsWe used electrophoresis of glycosaminoglycans of urine, determination of the activity of lysosomal enzymes in plasma, in dried blood spots according to the generally accepted method and DNA analysis.ResultsThe clinical symptomatology of 228 patients with Hunter syndrome was characterized by growth retardation, lesions of the bronchopulmonary, cardiovascular, nervous systems, etc. Thirty-five patients had an attenuated form of the disease. DNA was available from all patients. 19 patients from 10 families had a mild form of the disease. 42 patients from 41 families had an intermediate form of the disease. All other patients had a severe form of the disease. We provide brief clinical examples of some patients with a mild form of Hunter syndrome. Currently, 113 patients with Hunter syndrome receive enzyme replacement therapy (idursulfase or idursulfase beta).ConclusionThe long-term study of the large number of patients with Hunter syndrome helped identify disease-associated variants leading to severe and mild forms of the disease. The treatment effect and successful social adaptation of patients with a mild form of Hunter syndrome were revealed.
Highlights
This article presents the results of long-term observations and comparative analysis of genotype–phenotype features in a large group of patients (227 males and one female) with a severe, intermediate and mild form of Hunter syndrome, evaluating the quality and span of their lives, as well as their ability to social adaptation
1/5 of the patients had a papular rash with papules filled with glycolipid complexes and localized on the lateral and posterior surfaces of the thighs, shoulders and shoulder blades. This symptom is characteristic of Hunter syndrome which does not occur in patients with other types of mucopolysaccharidosis
The diagnosis of mucopolysaccharidosis type Mucopolysaccharidosis type II (II) (Hunter syndrome) consisted of four consecutive stages: 1—Assessment of phenotypic characters; 2—Determination of indicators of excretion of urinary glycosaminoglycans and their fractions, primarily heparan and dermatan sulfates; 3— Measurement of the activity of the lysosomal enzyme iduronate-2-sulfatase; 4—Deoxyribonucleic acid (DNA) diagnostics, including the search for nucleotide substitutions in the IDS gene with an estimate of its frequency and pathogenicity according to the International HMGD Database
Summary
This article presents the results of long-term observations and comparative analysis of genotype–phenotype features in a large group of patients (227 males and one female) with a severe, intermediate and mild form of Hunter syndrome, evaluating the quality and span of their lives, as well as their ability to social adaptation. The clinical symptoms of Hunter syndrome usually become noticeable during the first two years of life. After the first phenotype descriptions, two clinically different forms of Hunter syndrome were identified: a classical, severe form with severe somatic sings, progressive mental retardation, death at the age of 20 years or earlier; and a mild form characterized by longer life expectancy, fertility and minimal reduced intellect [8]. Later, it was suggested considering MPS II as a continuum between two extremes (severe and attenuated) [9]
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