Phenotypic Variability of LGMD 2C/R5 in a Genetically Homogenous Group of Bulgarian Muslim Roma.

Sarcoglycanopathies are among the most frequent and severe forms of autosomal recessive forms of limb-girdle muscular dystrophies (LGMDs) with childhood onset. Four subtypes are known: LGMDR3, LGMDR4, LGMDR5 and LGMDR6, which are caused, respectively, by mutations in the SGCA, SGCB, SGCG and SGCD genes. We present the clinical variability of LGMD 2C/R5 among a genetically homogeneous group of 57 patients, belonging to 35 pedigrees. Molecular genetic analysis showed that all 57 patients were homozygous for the C283Y variant. The muscles of the pelvic girdle and the trunk were affected early and were more severely affected, followed by the shoulder girdle. Macroglossia, hypertrophy of the calves, scapular winging and lumbar hyperlordosis were common in the ambulatory phase. A great intra and interfamilial variability in the clinical presentation of LGMD 2C/R5 was observed, despite having the same underlying molecular defect. Females demonstrated a relatively milder clinical course compared to males. Mean creatine phosphokinase (CK) CK levels were 20 times above normal values. Muscle computer tomography (CT) CT or MRIs showed earlier and more severe involvement of the flexor proximal limb muscles in comparison to extensor muscles.

Genetic Modifiers of ALS: The Impact of Chromogranin B P413L in a Bulgarian ALS Cohort.

This study investigated the role of the CHGB P413L variant (rs742710) in sporadic amyotrophic lateral sclerosis (sALS) within the Bulgarian population. We analyzed 150 patients with sALS (85 male and 65 female) for the presence of this variant, its potential impact on disease susceptibility, and age of onset. Genotyping was performed using PCR amplification and direct Sanger sequencing. Statistical analyses included comparisons with control data from GnomAD v2.1.1, one-way ANOVA, and Kaplan-Meier survival analysis. Results revealed a higher frequency of the minor T allele in patients with sALS compared to all control groups and a statistically significant increase in carrier genotypes compared to non-Finnish Europeans (χ2 = 15.4572, p = 0.000440). However, the impact on age of onset was less clear, with no statistically significant differences observed across genotypes or between carriers and non-carriers of the T allele. Kaplan-Meier analysis suggested a potential 2.5-year-earlier onset in T allele carriers, but the small sample size of carriers limits the reliability of this finding. Our study provides evidence for an association between the CHGB P413L variant and sALS susceptibility in the Bulgarian population, while its effect on age of onset remains uncertain, highlighting the need for further research in larger, diverse cohorts.

Identification and Characterization of Novel Founder Mutations in NDRG1: Refining the Genetic Landscape of Charcot-Marie-Tooth Disease Type 4D in Bulgaria.

Charcot-Marie-Tooth neuropathy type 4D (CMT4D) is a rare genetic disorder of the peripheral nervous system caused by biallelic mutations in the N-Myc Downstream Regulated 1 gene (NDRG1). Patients present with an early onset demyelinating peripheral neuropathy causing severe distal muscle weakness and sensory loss, leading to loss of ambulation and progressive sensorineural hearing loss. The disorder was initially described in the Roma community due to a common founder mutation, and only a handful of disease-causing variants have been described in this gene so far. Here, we present genetic and clinical findings from a large Bulgarian cohort of demyelinating CMT patients harboring recurrent and novel variants in the NDRG1 gene. Notably, two splice-site variants are exclusive to Bulgarian Muslims and reside in ancestral haplotypes, suggesting a founder effect. Functional characterization of these novel variants implicates a loss-of-function mechanism due to shorter gene products. Our findings contribute to a deeper understanding of the genetic and clinical heterogeneity of CMT4D and highlight novel founder mutations in the ethnic minority of Bulgarian Muslims.

Characterization of Clinical Phenotypes in Congenital Myasthenic Syndrome Associated with the c.1327delG Frameshift Mutation in CHRNE Encoding the Acetylcholine Receptor Epsilon Subunit.

Background: Congenital myasthenic syndromes (CMS) are a group of rare but often treatable inherited disorders of neuromuscular transmission characterized by fatigable skeletal muscle weakness. In this paper we present the largest phenotypic analysis to date of a cohort of patients carrying the pathogenic variant c.1327delG in the CHRNE gene, leading to CHRNE-CMS. Objective: This study aims to identify the phenotypic variability in CMS associated with c.1327delG mutation in the CHRNE gene. Methods: Disease specific symptoms were assessed using specific standardized tests for autoimmune myasthenia (Quantitative Myasthenia Gravis score) as well as patient-reported scales for symptom severity. Evaluated clinical manifestations included ocular symptoms (ophthalmoparesis and ptosis), bulbar weakness, axial muscle weakness, proximal and distal muscle weakness, and respiratory function. Patients were allocated into three groups according to clinical impression of disease severity: mild, moderate, and severe. Results: We studied 91 Bulgarian Roma patients, carrying the same causative homozygous CHRNE c.1327delG mutation. Bulbar weakness was present in patients throughout all levels of severity of CHRNE-CMS in this study. However, difficulties in eating and swallowing are more prominent characteristics in the moderate and severe clinical phenotypes. Diplopia and ptosis resulting from fatigue of the extraocular muscles were permanent features regardless of disease severity or age. Levels of axial, proximal and distal muscle weakness were variable between disease groups. The statistical analysis showed significant differences between the patients in the three groups, emphasizing a possible variation in symptom manifestation in the evaluated patient population despite the disease originating from the same genetic mutation. Impairment of respiratory function was more prominent in severely affected patients, which might result from loss of compensatory muscle function in those individuals. Conclusion: Results from our study indicate significant phenotypic heterogeneity leading to mild, moderate, or severe clinical manifestation in CHRNE-CMS, despite the genotypic homogeneity.

Clinical and genetic variability among Bulgarian patients with autosomal recessive spastic ataxia of Charlevoix-Saguenay.

BACKGROUND: Autosomal recessive spastic ataxia ofCharlevoix-Saguenay (ARSACS) is a rare neurodegenerative disorder characterizedby early-onset cerebellar ataxia, peripheral sensorimotor neuropathy, and lowerlimb spasticity. We present clinical andgenetic data of the first Bulgarian patients diagnosed with ARSACS by wholeexome sequencing (WES). METHODS: Variant filtering was performed usinglocally established pipeline and the selected variants were analysed by Sangersequencing. All patients underwent clinical examination and testingincluding the standard rating scales for spastic paraplegia and ataxia. RESULTS: Five different SACS gene variants, three of which novel, have been identified inpatients from three different ethnic groups. In addition to the classicalclinical triad, brain MRI revealed cerebellar atrophy, linear pontineT2-hypointensities, and hyperintense rim lateral tothalamus combined with retinal nerve fiber layer thickening on opticcoherence tomography (OCT). CONCLUSION: We expand the mutation, geographic, and phenotypic spectrum of ARSACS, adding Bulgaria to the world map of the disease, and drawing attention to the fact that it is still misdiagnosed. We demonstrated that brain MRI and OCT are necessary clinical tests for ARSACS diagnosis, even if one of the cardinal clinical features is lacking.

Essential components of an effective transition from paediatric to adult neurologist care for adolescents with Duchenne muscular dystrophy; a consensus derived using the Delphi methodology in Eastern Europe, Greece and Israel.

PURPOSE: An increasing number of patients with Duchenne muscular dystrophy (DMD) now have access to improved standard of care and disease modifying treatments, which improve the clinical course of DMD and extend life expectancy beyond 30 years of age. A key issue for adolescent DMD patients is the transition from paediatric- to adult-oriented healthcare. Adolescents and adults with DMD have unique but highly complex healthcare needs associated with long-term steroid use, orthopaedic, respiratory, cardiac, psychological, and gastrointestinal problems meaning that a comprehensive transition process is required. A sub-optimal transition into adult care can have disruptive and deleterious consequences for a patient's long-term care. This paper details the results of a consensus amongst clinicians on transitioning adolescent DMD patients from paediatric to adult neurologists that can act as a guide to best practice to ensure patients have continuous comprehensive care at every stage of their journey. METHODS: The consensus was derived using the Delphi methodology. Fifty-three statements were developed by a Steering Group (the authors of this paper) covering seven topics: Define the goals of transition, Preparing the patient, carers/parents and the adult centre, The transition process at the paediatric centre, The multidisciplinary transition summary - Principles, The multidisciplinary transition summary - Content, First visit in the adult centre, Evaluation of transition. The statements were shared with paediatric and adult neurologists across Central Eastern Europe (CEE) as a survey requesting their level of agreement with each statement. RESULTS: Data from 60 responders (54 full responses and six partial responses) were included in the data set analysis. A consensus was agreed across 100% of the statements. CONCLUSIONS: It is hoped that the findings of this survey which sets out agreed best practice statements, and the transfer template documents developed, will be widely used and so facilitate an effective transition from paediatric to adult care for adolescents with DMD.

Advancing the Understanding of Vesicle-Associated Membrane Protein 1-Related Congenital Myasthenic Syndrome: Phenotypic Insights, Favorable Response to 3,4-Diaminopyridine, and Clinical Characterization of Five New Cases.

BACKGROUND: Congenital myasthenic syndromes (CMS) are a group of inherited neuromuscular junction (NMJ) disorders arising from gene variants encoding diverse NMJ proteins. Recently, the VAMP1 gene, responsible for encoding the vesicle-associated membrane protein 1 (VAMP1), has been associated with CMS. METHODS: This study presents a characterization of five new individuals with VAMP1-related CMS, providing insights into the phenotype. RESULTS: The individuals with VAMP1-related CMS exhibited early disease onset, presenting symptoms prenatally or during the neonatal period, alongside severe respiratory involvement and feeding difficulties. Generalized weakness at birth was a common feature, and none of the individuals achieved independent walking ability. Notably, all cases exhibited scoliosis. The clinical course remained stable, without typical exacerbations seen in other CMS types. The response to anticholinesterase inhibitors and salbutamol was only partial, but the addition of 3,4-diaminopyridine (3,4-DAP) led to significant and substantial improvements, suggesting therapeutic benefits of 3,4-DAP for managing VAMP1-related CMS symptoms. Noteworthy is the identification of the VAMP1 (NM_014231.5): c.340delA; p.Ile114SerfsTer72 as a founder variant in the Iberian Peninsula and Latin America. CONCLUSIONS: This study contributes valuable insights into VAMP1-related CMS, emphasizing their early onset, arthrogryposis, facial and generalized weakness, respiratory involvement, and feeding difficulties. Furthermore, the potential efficacy of 3,4-DAP as a useful therapeutic option warrants further exploration. The findings have implications for clinical management and genetic counseling in affected individuals. Additional research is necessary to elucidate the long-term outcomes of VAMP1-related CMS.

Rare disease research workflow using multilayer networks elucidates the molecular determinants of severity in Congenital Myasthenic Syndromes.

Exploring the molecular basis of disease severity in rare disease scenarios is a challenging task provided the limitations on data availability. Causative genes have been described for Congenital Myasthenic Syndromes (CMS), a group of diverse minority neuromuscular junction (NMJ) disorders; yet a molecular explanation for the phenotypic severity differences remains unclear. Here, we present a workflow to explore the functional relationships between CMS causal genes and altered genes from each patient, based on multilayer network community detection analysis of complementary biomedical information provided by relevant data sources, namely protein-protein interactions, pathways and metabolomics. Our results show that CMS severity can be ascribed to the personalized impairment of extracellular matrix components and postsynaptic modulators of acetylcholine receptor (AChR) clustering. This work showcases how coupling multilayer network analysis with personalized -omics information provides molecular explanations to the varying severity of rare diseases; paving the way for sorting out similar cases in other rare diseases.

Clinical and Genotype Characteristics and Symptom Migration in Patients With Mixed Phenotype Transthyretin Amyloidosis from the Transthyretin Amyloidosis Outcomes Survey.

INTRODUCTION: Transthyretin amyloidosis (ATTR amyloidosis) is primarily associated with a cardiac or neurologic phenotype, but a mixed phenotype is increasingly described. METHODS: This study describes the mixed phenotype cohort in the Transthyretin Amyloidosis Outcomes Survey (THAOS). THAOS is an ongoing, longitudinal, observational survey of patients with ATTR amyloidosis, including both hereditary (ATTRv) and wild-type disease, and asymptomatic carriers of pathogenic transthyretin variants. Baseline characteristics of patients with a mixed phenotype (at enrollment or reclassified during follow-up) are described (data cutoff: January 4, 2022). RESULTS: Approximately one-third of symptomatic patients (n = 1185/3542; 33.5%) were classified at enrollment or follow-up as mixed phenotype (median age, 66.5 years). Of those, 344 (29.0%) were reclassified to mixed phenotype within a median 1-2 years of follow-up. Most patients with mixed phenotype had ATTRv amyloidosis (75.7%). The most frequent genotypes were V30M (38.9%) and wild type (24.3%). CONCLUSIONS: These THAOS data represent the largest analysis of a real-world mixed phenotype ATTR amyloidosis population to date and suggest that a mixed phenotype may be more prevalent than previously thought. Patients may also migrate from a primarily neurologic or cardiologic presentation to a mixed phenotype over time. These data reinforce the need for multidisciplinary evaluation at initial assessment and follow-up of all patients with ATTR amyloidosis. TRIAL REGISTRATION: ClinicalTrials.gov: NCT00628745.

Case Report: Transthyretin Glu54Leu-a rare mutation with predominant cardiac phenotype.

We report two unrelated Bulgarian families with hereditary transthyretin (ATTR) amyloidosis due to a rare p.Glu74Leu (Glu54Leu) pathogenic variant found in seven individuals-three of them symptomatic. Only one family with the same variant and with a Swedish origin has been clinically described so far. Our patients are characterized by predominant cardiac involvement, very much similar to the Swedish patients. Although the initial complaint was bilateral carpal tunnel syndrome, advanced amyloid cardiomyopathy was found in two symptomatic carriers at diagnosis with heart failure manifestations. The neurological involvement was considered as mild, with mainly sensory signs and symptoms being present. We followed a non-biopsy algorithm to confirm the diagnosis. Tafamidis 61 mg has been initiated as the only approved disease modifying treatment for ATTR cardiomyopathy. Clinical stability in the absence of adverse events has been observed at follow up.

Navigating the ALS Genetic Labyrinth: The Role of MAPT Haplotypes.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by wide clinical and biological heterogeneity, with a large proportion of ALS patients also exhibiting frontotemporal dementia (FTD) spectrum symptoms. This project aimed to characterize risk subtypes of the H1 haplotype within the MAPT (microtubule-associated protein tau) gene, according to their possible effect as a risk factor and as a modifying factor in relation to the age of disease onset. One hundred patients from Bulgaria with sporadic ALS were genotyped for the variants rs1467967, rs242557, rs1800547, rs3785883, rs2471738, and rs7521. Haploview 4.2 and SHEsisPlus were used to reconstruct haplotype frequencies using genotyping data from the 1000 Genomes project as controls. Genotype-phenotype correlation was investigated in the context of age of disease onset and risk of disease development. While the individual variants of the subtypes do not influence the age of onset of the disease, a correlation was found between the specific haplotype GGAGCA (H1b) and the risk of developing sALS, with results showing that individuals harboring this haplotype have a nearly two-fold increased risk of developing sALS compared to other H1 subtypes. The results from this study suggest that fine transcriptional regulation at the MAPT locus can influence the risk of ALS.

A 15-year consolidated overview of data in over 6000 patients from the Transthyretin Amyloidosis Outcomes Survey (THAOS).

BACKGROUND: Transthyretin amyloidosis (ATTR amyloidosis) is a progressive, multisystemic, life-threatening disease resulting from the deposition of variant or wild-type (ATTRwt amyloidosis) transthyretin amyloid fibrils in various tissues and organs. METHODS: Established in 2007, the Transthyretin Amyloidosis Outcomes Survey (THAOS) is the largest ongoing, global, longitudinal, observational study of patients with ATTR amyloidosis, including both hereditary and wild-type disease, and asymptomatic carriers of pathogenic TTR mutations. This analysis describes the baseline characteristics of symptomatic patients and asymptomatic gene carriers enrolled in THAOS since its inception in 2007 (data cutoff: August 1, 2022), providing a consolidated overview of 15-year data from the THAOS registry. RESULTS: This analysis included 4428 symptomatic patients and 1707 asymptomatic gene carriers. The majority of symptomatic patients were male (70.8%) with a mean (standard deviation [SD]) age at symptom onset of 56.6 (17.9) years. Compared with the 14-year analysis, V30M remained the most prevalent genotype in Europe (62.2%), South America (78.6%), and Japan (74.2%) and ATTRwt remained most common in North America (56.2%). Relative to the 14-year analysis, there was an increase of mixed phenotype (from 16.6 to 24.5%) and a reduction of predominantly cardiac phenotype (from 40.7 to 31.9%). The proportion of patients with predominantly neurologic phenotype remained stable (from 40.1 to 38.7%). Asymptomatic gene carriers were 58.5% female with a mean age at enrollment of 41.9 years (SD 15.5). CONCLUSIONS: This overview of > 6000 patients enrolled over 15 years in THAOS represents the largest registry analysis of ATTR amyloidosis to date and continues to emphasize the genotypic and phenotypic heterogeneity of the disease. Nearly a quarter of the symptomatic population within THAOS was mixed phenotype, underscoring the need for multidisciplinary management of ATTR amyloidosis. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT00628745.

Arginase deficiency in Bulgaria: first cases and potential endemic region for the disorder.

Arginase deficiency is an autosomal recessive urea cycle disorder caused by pathogenic variants in the ARG1 gene. The clinical features of the disease include spasticity, tremour, ataxia, hypotonia, microcephaly and seizures. Growth delay can also be observed in the affected individuals. Here we describe the results from molecular-genetic analysis of two patients with arginase deficiency. In the first case, we reported a novel homozygous missense variant c.775G>A p.(Gly259Ser) in a patient with Bulgarian ethnic origin. In the second case, a novel homozygous splice site variant c.329+1G>A was detected in a patient from a consanguineous family of Roma ethnic origin. A hundred samples of newborns of Roma origin were screened for variant c.329+1G>A and one individual was found to be a heterozygous carrier of variant c.329+1G> A. The results from this study indicated the necessity for screening of the Roma population with respect to the disease arginase deficiency in Bulgaria.

Novel variant c.92T > G (p.Val31Gly) in the PFN1 gene (ALS18) responsible for a specific phenotype in a large Bulgarian amyotrophic lateral sclerosis pedigree.

Objectives: Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder characterized by progressive deterioration of motor function, disability, and death. Variants in the PFN1 gene, encoding the Profilin-1 protein, are related to ALS18. Methods: We present a pedigree consisting of 3 generations and 4 affected individuals, 3 of which carry a novel heterozygous variant: c.92T > G (p.Val31Gly) in the PFN1 gene. This variant was discovered through means of whole exome sequencing (WES) and targeted analysis of ALS-related genes. Results: The mean age of onset in our pedigree was 59.75 (±10.11 SD) years with a significant difference between the first two generations (females) and the third (male) of 22.33 (±3.4 SD) years. For this ALS form, we observed a longer disease progression of 4 (±1.87 SD) years (three of four affected are still alive). Clinical manifestations displayed predominant impairment of the lower motor neuron (LMN) in one limb, with gradual involvement of other limbs. A novel heterozygous missense variant c.92T > G, p. Val31Gly (NM_005022.4) in exon 1 in the PFN1 gene was discovered through means of whole exome sequencing (WES). Segregation analysis in the family showed that the detected variant was inherited from the affected mother, and the affected aunt also turned out to be a variant carrier. Conclusions: ALS18 is a very rare form of the disease. We report here a relatively large pedigree with a novel variant, leading to late onset (after 50 years), initial involvement of the lower limbs and relatively slow progression.

Telemedicine in Neuromuscular Diseases During Covid-19 Pandemic: ERN-NMD European Survey.

BACKGROUND: Telemedicine (TM) contributes to bridge the gap between healthcare facilities and patients' homes with neuromuscular disease (NMD) because of mobility issues. However, its deployment is limited due to difficulties evaluating subtle neurological signs such as mild weakness or sensory deficits. The COVID-19 pandemic has disrupted healthcare delivery worldwide, necessitating rapid measures implementation by health care providers (HCPs) to protect patients from acquiring SARS-CoV-2 while maintaining the best care and treatment. OBJECTIVES: Given the challenges faced by remote healthcare assistance of NMD patients, we aim to evaluate the use of TM in NMD during the COVID-19 pandemic. METHODS: Based on the Model for Assessment-of-Telemedicine-Applications (MAST), we conducted a survey amongst clinicians of the ERN EURO NMD (European-Reference-Network-for-Rare-Neuromuscular-Diseases). RESULTS: Based on 42 responses over 76 expected ones, our results show that the COVID-19 pandemic significantly increased the number of HCPs using TM (from 60% to 100%). The TM types most used during the COVID-19 period are teleconsultation and consultation by phone, particularly in the context of symptoms worsening in NMD patients with COVID-19 infection. Most European HCPs were satisfied when using TM but as a complementary option to physical consultations. Many responses addressed the issue of technical aspects needing improvement, particularly for elderly patients who need caregivers' assistance for accessing the TM platform. CONCLUSIONS: TM has been essential during COVID-19, but its use still presents some limitations for NMD patients with cognitive deficits or for first-time diagnosis. Thus, TM should be used as complement to, rather than substitute, for face-to-face consultations.

Efficacy and safety of vutrisiran for patients with hereditary transthyretin-mediated amyloidosis with polyneuropathy: a randomized clinical trial.

BACKGROUND: The study objective was to assess the effect of vutrisiran, an RNA interference therapeutic that reduces transthyretin (TTR) production, in patients with hereditary transthyretin (ATTRv) amyloidosis with polyneuropathy. METHODS: HELIOS-A was a phase 3, global, open-label study comparing the efficacy and safety of vutrisiran with an external placebo group (APOLLO study). Patients were randomized 3:1 to subcutaneous vutrisiran 25 mg every 3 months (Q3M) or intravenous patisiran 0.3 mg/kg every 3 weeks (Q3W) for 18 months. RESULTS: HELIOS-A enrolled 164 patients (vutrisiran, n = 122; patisiran reference group, n = 42); external placebo, n = 77. Vutrisiran met the primary endpoint of change from baseline in modified Neuropathy Impairment Score +7 (mNIS+7) at 9 months (p = 3.54 × 10-12), and all secondary efficacy endpoints; significant improvements versus external placebo were observed in Norfolk Quality of Life-Diabetic Neuropathy, 10-meter walk test (both at 9 and 18 months), mNIS+7, modified body-mass index, and Rasch-built Overall Disability Scale (all at 18 months). TTR reduction with vutrisiran Q3M was non-inferior to within-study patisiran Q3W. Most adverse events were mild or moderate in severity, and consistent with ATTRv amyloidosis natural history. There were no drug-related discontinuations or deaths. CONCLUSIONS: Vutrisiran significantly improved multiple disease-relevant outcomes for ATTRv amyloidosis versus external placebo, with an acceptable safety profile. CLINICALTRIALS.GOV: NCT03759379.

Seven Years of Selective Genetic Screening Program and Follow-Up of Asymptomatic Carriers With Hereditary Transthyretin Amyloidosis in Bulgaria.

Hereditary transthyretin amyloidosis (ATTRv amyloidosis) is a rare, autosomal-dominant (AD) multisystem disorder resulting from the extracellular deposition of amyloid fibrils formed by a destabilized mutant form of transthyretin (TTR), a transport protein predominantly produced by the liver. Aim: The aims of the current study are to demonstrate the Bulgarian experience with the screening programs among the high-risk patient population over the last 7 years, to present the results from the therapy with TTR stabilizer in our cohort, as well as to stress on the importance of a follow-up of asymptomatic carriers with TTR pathogenic variants by a multidisciplinary team of specialists. Materials and Methods: In 2014, a screening program among the high-risk patient population for ATTRv was initiated in Bulgaria. On one hand, it was conducted to identify new patients and families among people with "red flag" clinical features, while on the other hand, the program aimed to identify TTR mutation carriers among the families with already genetically proven diagnoses. Sanger sequencing methodology was used to make fast target testing for mutations in the TTR gene in the suspected individuals. All of the identified carriers underwent subsequent evaluation for neurological, cardiac, gastroenterological, and neuro-ophthalmological involvement. Those considered affected were provided with multidisciplinary treatment and a follow-up. Results: As a result of a 7-year selective screening program among the high-risk patient population and relatives of genetically verified affected individuals, 340 carriers of TTR mutations were identified in Bulgaria with the following gene defects: 78.53% with Glu89Gln, 10.29% with Val30Met, 8.24% with Ser77Phe, 2.06% with Gly47Glu, and 0.59% with Ser52Pro. All of these affected displayed a mixed phenotype with variable ages at onset and rate of progression, according to their mutation. From the 150 patients treated with TTR stabilizer, 84 remained stable, while in other 66 patients the treatment was terminated either because of polyneuropathy progression or due to death. A program for a regular follow-up of asymptomatic carriers in the last 3 years enabled us to detect the transition of 39/65 to symptomatic patients and to initiate treatment in a timely manner. Conclusion: Bulgarian ATTRv patients display a mixed phenotype with some clinical peculiarities for each mutation that should be considered when treating the affected and the follow-up of the asymptomatic carriers of a specific gene defect.

Determination of Tafamidis Plasma Concentrations in Amyloidosis Patients with Glu89Gln Mutation by HPLC-UV Detection.

Present study describes a high-performance liquid chromatography method for the determination of the potent kinetic stabilizer-Tafamidis in human plasma. It was approved for medical use in European Union in 2011. Ultra violet (UV) detection mode and isocratic elution of the mobile phase were set and made the analytical procedure fast and widely applicable. Chromatographic determination was performed on a Purospher® RP-18 column. The mobile phase consisted of 0.1% trifluoroacetic acid in water and acetonitrile in the ratio 42:58 v/v and the flow rate was 1.0 ml/min. All analyses were carried at a room temperature and the detector was set at 280 nm. Calibration curve over a range of 1.00-10.00 µM was constructed for the purposes of linearity method validation. The specificity and effectiveness of the developed method made it suitable for observation of patients' plasma Tafamidis concentration with time and drug therapy monitoring.