[Gerstmann-Sträussler disease: a familial case with common PRNP mutation and atypical features]. / Bolezn' Gerstmana­Shtrosslera: semeinyi sluchai s chastoi mutatsiei gena PRNP i atipichnymi proyavleniyami.

Gerstmann-Sträussler disease (GSD) is a very rare autosomal dominant late-onset neurodegenerative disorder related to prion protein gene PRNP. Mutation p.Pro102Leu produces about 80% of cases, which are often named GSD-102. DNA testing provides exact diagnosis. In the presented Russian family there were 3 patients: a female index case, age 32 years, her brother, age 37 years (age of onset in both is 27 years) and their deceased father (onset in 35 years, death in 44 years). GSD was not suspected until whole exome sequencing in the female detected PRNP mutation p.Pro102Leu confirmed in her and in the brother by Sanger sequencing. Atypical features of the case are: early onset in siblings, absence of mental and behavioral problems in the female and in the father and mild disturbances in the brother; epilepsy in the brother; atypical onset with transient signs in the brother. Other intrafamilial differences are prevailing spastic paraparesis in the female in contrast to predominant ataxia in the brother and dysarthria absence in the female. The case illustrates GSD-102 variability, complicating clinical diagnostics.

Genetic Landscape of Nephropathic Cystinosis in Russian Children.

Nephropathic cystinosis is a rare autosomal recessive disorder characterized by amino acid cystine accumulation and caused by biallelic mutations in the CTNS gene. The analysis methods are as follows: tandem mass spectrometry to determine the cystine concentration in polymorphonuclear blood leukocytes, Sanger sequencing for the entire coding sequence and flanking intron regions of the CTNS gene, multiplex PCR to detect a common mutation-a 57 kb deletion, and multiplex ligation-dependent probe amplification to analyze the number of exon copies in the CTNS gene. Haplotype analysis of chromosomes with major mutations was carried out using microsatellite markers D17S831, D17S1798, D17S829, D17S1828, and D17S1876. In this study, we provide clinical, biochemical, and molecular genetic characteristics of 40 Russian patients with mutations in the CTNS gene, among whom 30 patients were selected from a high-risk group of 85 people as a result of selective screening, which was carried out through cystine concentration measurement in polymorphonuclear blood leukocytes. The most common pathogenic variant, as in most described studies to date, was the 57 kb deletion, which represented 25% of all affected alleles. Previously non-described variants represented 22.5% of alleles. The founder effect in the Karachay and Chechen ethnic groups was shown for the following major variants: c.1015G > A and c.518A > G.

[Atypical spastic paraplegia type 4 due to p.Arg499His mutation in SPAST gene]. / Atipichnaya spasticheskaya paraplegiya 4-go tipa s mutatsiei p.Arg499His gena SPAST.

A case of spastic paraplegia type 4 (SPG4) due to SPAST p.Arg499His mutation de novo in a child, aged 2 years 8 months, is presented. The differences of this first Russian case with the mutation and of a number of reported cases from typical SPG4 are very early onset, severe disabling spasticity and additional signs, cognitive disturbances in particular; SPAST mutations de novo are also infrequent. Specific patterns point to the relationship between genotype and phenotype. Methods of exome sequencing are particularly informative in atypical cases difficult for clinical diagnostics.

A Mosaic Mutation in the LAMA2 Gene in a Case of Merosin-deficient Congenital Muscular Dystrophy.

Merosine deficient congenital muscular dystrophy is one of the most common forms of congenital muscular dystrophy. This disease is caused by a primary deficiency or a functionally inactive form of the protein merosin in muscle tissue. The type of inheritance of this disease is autosomal recessive. De novo variants with this type of inheritance are rare, and it is quite possible that the de novo variant may hide a mosaic form in the parent of an affected child. We present a birth family with two affected children who inherited a previously undescribed pathogenic variant c.1755del from their mother and a previously described pathogenic variant c.9253C > T in the LAMA2 gene from their mosaic father. LAMA2 gene mutation analysis was performed by mass parallel sequencing and direct sequencing of genomic DNAs.

[Diversity of CACNA1A-related disorders]. / Raznoobrazie boleznei, svyazannykh s genom CACNA1A.

Four cases of autosomal dominant CNS disorders related to CACNA1A mutations and detected by massive parallel sequencing are reported: a non-familial case of episodic ataxia type 2 (EA2) with the previously reported mutation c.269_270insA (p.Tyr90Ter) in a 35-year-old man; familial hemiplegic migraine type 1 (FHM1) in a girl aged 3 years 10 months and her mother aged 38 yrs with a novel mutation 1829C>T (p.Ser610Phe), members of a family with 4 patients and incomplete penetrance; developmental and epileptic encephalopathy 42 (DEE42) in a 9-year-old girl and a 5-year-old boy from different families with the identical de novo mutation c.2137G>A (p.Ala713Thr) reported earlier. Clinical and genetic characteristics are analyzed compared to literature.

HINT1 gene pathogenic variants: the most common cause of recessive hereditary motor and sensory neuropathies in Russian patients.

Pathogenic variants in the HINT1 gene lead to hereditary axonopathy with neuromyotonia. However, many studies show that neuromyotonia may remain undiagnosed, while axonopathy is the major clinical finding. The most common cause of neuromyotonia and axonopathy, especially in patients of Slavic origin, is a c.110G>C (p.Arg37Pro) pathogenic variant in homozygous or compound heterozygous state. In this study, we analyzed a peripheral neuropathy caused by pathogenic variants in the HINT1 gene and evaluated its contribution to the hereditary neuropathy structure. The studied group included 1596 non-related families diagnosed with hereditary motor and sensory neuropathy (HMSN). The results show that HINT1 gene pathogenic variants make a significant contribution to the hereditary neuropathy epidemiology in Russian patients. They account for at least 1.9% of all HMSN cases and 9% of axonopathy cases. The most common HINT1 pathogenic variant in Russian patients is the c.110G>C (p.Arg37Pro) substitution. Its allelic frequency is 0.2% (95% CI 0.19-0.21%), carrier frequency is 1 in 250 people in Russian Federation, and the estimated disease incidence is 1 in 234,000 individuals. It was determined that the cause of this pathogenic variant's prevalence is the founder effect.

[Ataxia-telangiectasia with rare phenotype and unusual pedigree]. / Ataksiia-teleangiéktaziia s redkim fenotipom i neobychnoi rodoslovnoi.

The authors present an unique familial case of ataxia-telangiectasia (AT) mimicking autosomal dominant inheritance with different phenotypes in a 3-year-old boy (ataxia and moderate dyskinesia since 1.5 years) and his 31-year-old mother (mild dystonia, predominantly torticollis, since 10 years). Exome sequencing of the boy detected two heterozygous ATM mutations c.1564_1565delGA (p.Glu522fs) and c.6154G>A (p.Glu2052Lys) reported earlier. Sanger sequencing found both mutations in the child, the father was heterozygous for c.1564_1565delGA, the mother for 6154G>A earlier reported in the rare A-T phenotype of 'pure' local dystonia. Exome sequencing of the mother, who considered herself healthy, detected the allelic ATM mutation c.7630-2A>C in intron 51.

[Coincidence of hereditary motor and sensory neuropathy type 1A and limb girdle muscular dystrophy type 2A]. / Cochetanie nasledstvennoi motorno-sensornoi neiropatii 1A tipa i poiasno-konechnostnoi myshechnoi distrofii 2A tipa.

A rare case of two neuromuscular disorders in a 29-year-old female is presented: autosomal dominant hereditary motor and sensory neuropathy type 1A (HMSN1A) due to PMP22 duplication and autosomal recessive limb girdle muscular dystrophy type 2A (LGMD2A) produced by CAPN3 common mutation c.550delA and novel c.575C>G (p.Thr192Ser).Walking difficulties appeared in 27 years, the patient had signs of both disorders, more of LGMD, but was not disabled. HMSN1A was inherited from her father whose disease was not recognized earlier.

[Clinical-genetic correlations in the hereditary motor-sensor neuropathy caused by mutations in the MPZ (P0) gene].

Hereditary motor-sensor neuropathy (HMSN) caused by mutations in the MPZ (P0) gene is a rare variant of hereditary demyelinating polyneuropathies that makes up 5-10% of all cases in different populations. Based on the complex examination of patients of the Russian Federation with different MPZ (P0) mutations, we obtained clinical-genetic, electromyographic and molecular-genetic characteristics of HMSN caused by mutations in the MPZ (P0) gene. Peculiarities of clinical presentations in patients with HMSN, types 1B and 2I, are presented. Diagnostic criteria of these genetic variants have been formed. The new allelic variants of HMSN caused by mutations in the MPZ (P0) gene are described. The distribution of mutations by protein domains has been analyzed.

[Spectrum and frequency of mutations in the connexin 32 gene (GJB1) in hereditary and sensory neuropathy type 1X patients from Bashkortostan].

Hereditary motor and sensory neuropathy type 1X (HMSN 1X) is the second most frequent form of demyelinating polyneuropathies and is caused by mutations in the gene for connexin 32 protein (Cx32, GJB1). The contribution of HMSN 1X to the structure of HMSN in the Republic of Bashkortostan was determined. The GJB1 mutations were detected in 18 out of 131 unrelated patients, which constituted 13.7%. The four missense mutations identified were represented by: Pro87Ala (c.259C>G) with the frequency of 10%; Arg22Gln (c.65G>A) (2.98%); Arg15Gln (c.44G>A); and Thr86Ile (c.257C