Analysis of long-term observations of the large group of Russian patients with Hunter syndrome (mucopolysaccharidosis type II).

BACKGROUND: 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. METHODS: We 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. RESULTS: The 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). CONCLUSION: The 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.

Epidemiology and Genetics of Mucopolysaccharidosis Type VI in Russia.

Mucopolysaccharidosis VI (MPS VI) is an autosomal recessive lysosomal storage disease caused by mutations in the arylsulfatase B gene (ARSB) and consequent deficient activity of ARSB, a lysosomal enzyme involved in the glycosaminoglycan (s) (GAGs) metabolism. Here, we present the results of the study of ARSB DNA analysis in MPS VI patients in the Russian Federation (RF) and other republics of the Former Soviet Union. In a cohort of 68 patients (57 families) with MPS VI, a total of 28 different pathogenic alleles were found. The most prevalent nucleotide changes included NM_000046.5:c.194C>T and NM_000046.5:c.454C>T. Five pathogenic alleles were novel, not previously reported (NM_000046.5:c.304C>G, NM_000046.5:c.533A>G, NM_000046.5:c.941T>C, NM_000046.5:c.447_456del10, and NM_000046.5:c.990_10003del14). The nucleotide variant NM_000045.6:c.454C>T was the prevalent allele among Slavic Russian patients. The nucleotide variant NM_000045.6:c.194C>T was found only in MPS VI families from the Republic of Dagestan. Based on the analysis of dry blood spots (DBSs) collected from newborns in this RF region, we showed the frequency of this mutant allele in the Republic of Dagestan to be 0.01 corresponding to the MPS VI frequency of nearly 1:10,000, which is one of the highest worldwide. This may eventually make the selective asymptomatic carrier test and newborn screening highly feasible in this region of the country.

Homocystinuria due to cystathionine beta-synthase (CBS) deficiency in Russia: Molecular and clinical characterization.

We present the results of the 45-year clinical observation of 27 Russian homocystinuria patients. We made a mutation analysis of the CBS gene for thirteen patients from eleven unrelated genealogies. All patients except for the two were compound heterozygotes for the mutations detected. The most frequent mutation in the cohort investigated was splice mutation IVS11-2a->c. We detected one new nonsense mutation, one new missense-mutation and three novel small deletions. We also report the clinical case of the B6-responsive patient genotyped as Ile278Thr/Cys109Arg.

Attenuated osteoarticular phenotype of type VI mucopolysaccharidosis: a report of four patients and a review of the literature.

Mucopolysaccharidosis type VI (Maroteaux-Lamy syndrome, MPS VI, OMIM 253200) is caused by mutations in the gene coding for N-acetylgalactosamine-4-sulfatase (4-sulfatase, arylsulfatase B, ARSB, EC 3.1.6.12), a lysosomal enzyme involved in the degradation of dermatan sulfate (DS). The clinical presentation of MPS VI varies greatly with respect to age of onset and rate of disease progression. This report focuses on the attenuated form of MPS VI, which can go unrecognized for years and often presents with atypical signs or symptoms. We described a cohort of MPS VI patients (n = 4) heterozygous for the p.Y210C mutation who had a significant osteoarticular involvement at the onset of their disease and who were diagnosed years or even decades later. We have also reviewed the literature (n = 36). Two types of attenuated MPS VI phenotypes could be distinguished: osteoarticular and cardiac. The majority of MPS VI patients reported so far as relatively attenuated presented with an essentially osteoarticular phenotype associated with the p.Y210C mutation. Patients homozygous for the p.R152W mutation presented with a cardiac phenotype, which, despite fulfilling the generally used criteria for attenuated phenotype, may lead to fast disease progression and abrupt death. The knowledge of natural history and genotype-phenotype correlation may help in developing a tailored therapy potentially using enzyme replacement therapy with substrate reduction therapy or chaperones.

Mucopolysaccharidosis type VI in Russia, Kazakhstan, and Central and Eastern Europe.

BACKGROUND: The aim of this study was to describe the natural clinical course, incidence and prevalence of mucopolysaccharidosis type VI (MPS VI) in Russia, Kazakhstan, and Central and Eastern Europe. METHODS: Patients (n = 49) were identified by retrieving the data from eight international centers for MPS VI. RESULTS: A large number of patients presented with an attenuated phenotype (33%). Height and genotype were related to the severity of the disease, while no clear trend was observed between height and urinary glycosaminoglycan level. A high prevalence of the p.R152W mutation was observed both in the whole series (42%) as well as in Russian patients (43%). The incidence rate ranged from 0.0363 to 0.64 per 100,000 live births in Poland and Lithuania, respectively. CONCLUSIONS: The observed high p.R152W carrier frequency in the Lithuanian population may indicate a possible founder effect in this region. The high prevalence of this mutation observed in the whole series, as well as the Slavic origin of the majority of patients homozygous for this mutation, suggest that p.R152W may be of Slavic, not Lithuanian origin. Resettlement of the Polish population after World War II resulted in dilution of the prevalence of carriers in Poland and a very low MPS VI incidence.

Mucopolysaccharidosis type VI: a predominantly cardiac phenotype associated with homozygosity for p.R152W mutation in the ARSB gene.

Mucopolysaccharidosis type VI (MPS VI) is a rare lysosomal, autosomal recessive storage disorder caused by deficient activity of N-acetylgalactosamine-4-sulfatase (ARSB). Approximately, 140 ARSB gene mutations have been identified; however, most are private mutations making genotype-phenotype correlation for most MPS VI patients difficult. The aim of this study was to describe the natural clinical course in patients homozygous for the p.R152W mutation from eight unrelated families. From our database of 70 patients with MPS VI, we selected 10 patients homozygous for the p.R152W mutant allele (median age 27.5 years, range 18-38 years). We performed a cross-sectional observational study characterizing the onset and prevalence of clinical manifestations. First signs of the disease, such as cardiac valve disease, slightly decreased joint range of motion and mild growth retardation, were observed in mid-adolescent years (median 15 years). Within the disease course, the most common clinical feature in all the patients was progressive heart disease of predominantly valve origin leading to symptoms of heart failure. Other typical MPS VI features were subtle and not present in all the patients. Delays up to 23 years (median 8.5 years) intervened between symptom onset and disease diagnosis. Patients homozygous for the p.R152W mutation present a cardiac variant of MPS VI characterized by progressive cardiac valve disease leading to serious cardiac complications including abrupt death due to cardiac failure.