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Glaucoma is a neurodegenerative disorder characterized by thinning of neuroretinal rim, enlarged cup-to-disc ratio (CDR) and visual field damage. Although raised intraocular pressure is main risk factor for development of glaucoma, it can occur with consistently normal measurements in the intraocular pressure as normal tension glaucoma (NTG). Enlargement of CDR is a classical sign of glaucoma, but it can also result from non-glaucomatous optic neuropathies such as Leber hereditary optic neuropathy (LHON). We describe a case of LHON with increased CDR, discuss its differential diagnosis with NTG and highlight the reasons for misdiagnoses between these two entities. [ABSTRACT FROM AUTHOR]

Auditory neuropathy is a type of hearing loss that constitutes a change in the conduct of the auditory stimulus by the involvement of inner hair cells or auditory nerve synapses. It is characterized by the absence or alteration of waves in the examination of brainstem auditory evoked potentials, with otoacoustic and/or cochlear microphonic issues. At present, four loci associated with non-syndromic auditory neuropathy have been mapped: Autosomal recessive deafness-9 [DFNB9; the otoferlin (OTOF) gene] and autosomal recessive deafness-59 [DFNB59; the pejvakin (PJVK) gene], associated with autosomal recessive inheritance; the autosomal dominant auditory neuropathy gene [AUNA1; the diaphanous-3 (DIAPH3) gene]; and AUNX1, linked to chromosome X. Furthermore, mutations of connexin 26 [the gap junction β2 (GJB2) gene] have also been associated with the disease. OTOF gene mutations exert a significant role in auditory neuropathy. In excess of 80 pathogenic mutations have been identified in individuals with non-syndromic deafness in populations of different origins, with an emphasis on the p.Q829X mutation, which was found in ~3% of cases of deafness in the Spanish population. The identification of genetic alterations responsible for auditory neuropathy is one of the challenges contributing to understand the molecular bases of the different phenotypes of hearing loss. Thus, the present study aimed to investigate molecular changes in the OTOF gene in patients with auditory neuropathy, and to develop a DNA chip for the molecular diagnosis of auditory neuropathy using mass spectrometry for genotyping. Genetic alterations were investigated in 47 patients with hearing loss and clinical diagnosis of auditory neuropathy, and the c.35delG mutation in the GJB2 gene was identified in three homozygous patients, and the heterozygous parents of one of these cases. Additionally, OTOF gene mutations were tracked by complete sequencing of 48 exons, although these results are still preliminary. Studying the genetic basis of auditory neuropathy is of utmost importance for obtaining a differential diagnosis, developing more specific treatments and more accurate genetic counseling. [ABSTRACT FROM AUTHOR]

Background: Mutations in the mitochondrial DNA (mtDNA) have been associated with aminoglycoside-induced and nonsyndromic deafness in different populations. In the present study, we investigated the contribution of mutations in mitochondrial genes to the etiology of hearing loss in a Brazilian sample. Methods: Using mass spectrometry genotyping technology, combined with direct sequencing, 50 alterations previously described in 14 mitochondrial genes were screened in 152 patients with sensorineural hearing loss and in104 normal hearing controls. Results: Fifteen known mitochondrial alterations were detected (G709A, A735G, A827G, G988A, A1555G, T4363C, T5628C, T5655C, G5821A, C7462T, G8363A, T10454C, G12236A, T1291C, G15927A). Pathogenic mutations in MT-RNR1 and MT-TK genes were detected in 3 % (5/152) of the patients with hearing loss. Conclusions: This study contributed to show the spectrum of mitochondrial variants in Brazilian patients with hearing loss. Frequency of A1555G was relatively high (2.6 %), indicating that this mutation is an important cause of hearing loss in our population. This work reports for the first time the investigation and the detection of the tRNALys G8363A mutation in Brazilian patients with maternally inherited sensorineural hearing loss. [ABSTRACT FROM AUTHOR]

Background: Recent advances in molecular genetics have enabled to determine the genetic causes of non-syndromic hearing loss, and more than 100 genes have been related to the phenotype. Due to this extraordinary genetic heterogeneity, a large percentage of patients remain without any molecular diagnosis. This condition imply the need for new methodological strategies in order to detect a greater number of mutations in multiple genes. In this work, we optimized and tested a panel of 86 mutations in 17 different genes screened using a high-throughput genotyping technology to determine the molecular etiology of hearing loss. Methods: The technology used in this work was the MassARRAY iPLEX® platform. This technology uses silicon chips and DNA amplification products for accurate genotyping by mass spectrometry of previous reported mutations. The generated results were validated using conventional techniques, as direct sequencing, multiplex PCR and RFLP-PCR. Results: An initial genotyping of control subjects, showed failures in 20 % of the selected alterations. To optimize these results, the failed tests were re-designed and new primers were synthesized. Then, the specificity and sensitivity of the panel demonstrated values above 97 %. Additionally, a group of 180 individuals with NSHL without a molecular diagnosis was screened to test the diagnostic value of our panel, and mutations were identified in 30 % of the cases. In 20 % of the individuals, it was possible to explain the etiology of the HL. Mutations in GJB2 gene were the most prevalent, followed by other mutations in in SLC26A4, CDH23, MT-RNR1, MYO15A, and OTOF genes. Conclusions: The MassARRAY technology has the potential for high-throughput identification of genetic variations. However, we demonstrated that optimization is required to increase the genotyping success and accuracy. The developed panel proved to be efficient and cost-effective, being suitable for applications involving the molecular diagnosis of hearing loss. [ABSTRACT FROM AUTHOR]

Single nucleotide polymorphisms (SNPs) are important markers in many studies that link DNA sequence variations to phenotypic changes; such studies are expected to advance the understanding of human physiology and elucidate the molecular basis of diseases. The DFNB1 locus, which contains the GJB2 and GJB6 genes, plays a key role in nonsyndromic hearing loss. Previous studies have identified important mutations in this locus, but the contribution of SNPs in the genes has not yet been much investigated. The aim of this study was to investigate the association of nine polymorphisms located within the DFNB1 locus with the occurrence of autosomal recessive nonsyndromic hearing loss (ARNSHL). The SNPs rs3751385 (C/T), rs7994748 (C/T), rs7329857 (C/T), rs7987302 (G/A), rs7322538 (G/A), rs9315400 (C/T), rs877098 (C/T), rs945369 (A/C), and rs7333214 (T/G) were genotyped in 122 deaf patients and 132 healthy controls using allele-specific PCR. There were statistically significant differences between patients and controls, in terms of allelic frequencies in the SNPs rs3751385, rs7994748, rs7329857, rs7987302, rs945369, and rs7333214 (P<0.05). No significant differences between the two groups were observed for rs7322538, rs9315400, and rs877098. Our results suggest that SNPs present in the GJB2 and GJB6 genes may have an influence on ARNSHL in humans. [ABSTRACT FROM AUTHOR]

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Objective: Evaluation of the effectiveness of imaging and genetic testing, and establishment of a cost-effective diagnostic protocol for the etiologic diagnosis of sensorineural hearing loss (SNHL) in Brazil. Design: Prospective cohort study. Study sample: Analysis of 100 unrelated Brazilian patients with severe to profound bilateral SNHL submitted to cochlear implant (CI) between 2002 and 2010 at the University of Campinas hospital. The study was based upon three groups: individuals with congenital, progressive, and sudden SNHL. Results: After the diagnostic investigation, the number of cases with unknown etiology was reduced from 72 to 42 (a 42% reduction); 25% of cases were due to environmental factors, 19% to genetic causes, and 14% to inner-ear abnormalities or other clinical features. The genetic and imaging findings contributed to the diagnosis of SNHL in 19% and 20% of the cases analysed, respectively. Molecular testing mainly contributed to the diagnosis of patients with congenital SNHL, while the contribution of radiologic examination was higher for individuals with progressive or sudden SNHL. A sequential diagnostic protocol was proposed based on these data. Conclusions: The proposed diagnostic workup algorithm could provide better optimization of etiologic diagnosis, as well as reduced costs, compared to a simultaneous testing approach. [ABSTRACT FROM AUTHOR]

Copyright of Revista Brasileira em Promoção da Saúde is the property of Revista Brasileira em Promocao da Saude and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Purpose: The aim of this study was to describe clinical features and search for primary mitochondrial DNA (mtDNA) mutations in 13 unrelated Brazilian patients with Leber’s hereditary optic neuropathy (LHON). Methods: Analysis of the G11778A, G3460A, and T14484C mutations was done by polymerase chain reaction and restriction fragment length polymorphism, and mutations were confirmed by direct sequencing. Mean age of onset was 24.5 years and all cases were bilateral. Results: Sex ratio (12M:1F) and frequency of simultaneous involvement (9/13) were higher than in other studies. In nine cases there was familial recurrence: 24 male and two female relatives. Ten patients had a mutation: G11778A in six, T14484C in three and one G3460A. The frequency of patients bearing a primary mutation was lower than that described in multicentric studies but similar to that observed among Asians. A higher frequency of the T14484C mutation was detected. Conclusions: The contribution of Amerindians and Africans to the Brazilian mtDNA pool may account for differences in the type and frequency of primary LHON mutations. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the issue on topics including molecular mechanism of vestibular schwannoma, hearing loss in osteogenesis imperfecta, and distribution of mutations in pediatric patients.

Abstract: Hearing impairment is the most prevalent sensorial deficit in the general population. Congenital deafness occurs in about 1 in 1000 live births, of which approximately 50% has hereditary cause in development countries. Non-syndromic deafness can be caused by mutations in both nuclear and mitochondrial genes. Mutations in mtDNA have been associated with aminoglycoside-induced and non-syndromic deafness in many families worldwide. However, the nuclear background influences the phenotypic expression of these pathogenic mutations. Indeed, it has been proposed that nuclear modifier genes modulate the phenotypic manifestation of the mitochondrial A1555G mutation in the MTRNR1 gene. The both putative nuclear modifiers genes TRMU and MTO1 encoding a highly conserved mitochondrial related to tRNA modification. It has been hypothesizes that human TRMU and also MTO1 nuclear genes may modulate the phenotypic manifestation of deafness-associated mitochondrial mutations. The aim of this work was to elucidate the contribution of mitochondrial mutations, nuclear modifier genes mutations and aminoglycoside exposure in the deafness phenotype. Our findings suggest that the genetic background of individuals may play an important role in the pathogenesis of deafness-associated with mitochondrial mutation and aminoglycoside-induced. [Copyright &y& Elsevier]

HDR syndrome is a rare autosomal dominant disorder caused by mutations in the GATA3 gene and characterized by hypoparathyroidism, sensorineural deafness and renal abnormalities. Here we report a Brazilian family, from which the proband, his mother and his grandfather were diagnosed with bilateral sensorineural hearing loss. Molecular screening of the GJB2, GJB6 and MTRNR1 genes in the proband showed no alterations; however, whole exome sequencing detected a heterozygous mutation, c.1099C > T (p.Arg367*), in the GATA3 gene. Segregation analyses showed that the mother also had the mutation, but not the grandparents, hence indicating a different hearing impairment type for the grandfather. Paternity test of the mother of the proband confirmed that she has a de novo mutation. Furthermore, HDR syndrome was confirmed with new clinical evaluations showing right kidney agenesis in the proband. This is the first study reporting only deafness and renal abnormalities as symptoms of the p.Arg367* mutation in the GATA3 gene, and also the sixth HDR syndrome case in the world, and the first on the American continent. Together with other reported cases, this study highlights the variability of HDR syndrome symptoms in individuals with the p.Arg367* mutation, emphasizing the importance of molecular analyses for correct diagnosis.

Purpose: Leber hereditary optic neuropathy (LHON) is a mitochondrial inherited disease characterized by bilateral vision problems, such as reduced visual acuity, dyschromatopsia, and central or centrocecal scotoma. Of these cases, 95% are caused by three mutations in mitochondrial DNA (mtDNA): m.G11778A, followed by m.T14484C and m.G3460A. The remaining 5% of cases of LHON are caused by rare mutations also present in mtDNA. Although conventional molecular tools for molecular screening of LHON are becoming popular, in most cases these tools are still expensive and time-consuming and are difficult to reproduce. Therefore, to meet the need for more accurate, faster, and cheaper techniques for molecular screening, as well as make it more accessible, we used the high-throughput method TaqMan ® OpenArray ™ Genotyping platform for developing a customized high-throughput assay for the three main mutations related to LHON., Methods: The assay was performed for 87 individuals diagnosed with LHON or acquired optic neuropathy of unknown origin. The three main mutations were screened using the customized assay with the TaqMan ® OpenArray ™ Genotyping platform, and all reactions were performed in triplicate. The positive and negative results were revalidated with restriction fragment length polymorphism PCR (RFLP-PCR) and Sanger sequencing., Results: The main mutations related to LHON were detected in 34 patients with genotyping reactions, of which 27 cases had the m.G11778A mutation, and seven had the m.T14484C mutation., Conclusions: The TaqMan ® OpenArray ™ Genotyping platform was shown to be an effective tool for molecular screening of the most common mutations related to LHON without presenting false positive or negative results for the analyzed mutations. In addition, this tool can be considered a cheaper, faster, and more accurate alternative for molecular screening of LHON mutations than PCR and Sanger sequencing, as 94 genotyping reactions can be performed within 6 h and specific TaqMan probes are used.

Objectives: Ménière's disease (MD) is a complex disease of unknown etiology characterized by a symptomatic tetrad of vertigo, hearing loss, tinnitus, and aural fullness. In addition to factors related to homeostasis of the inner ear, genetic factors have been implicated in its pathophysiology, including genes related to the transport of water and ionic composition maintenance of the endolymph, such as the aquaporin genes AQP2 and AQP3, and the potassium channel gene KCNE1. The aim of this study was to identify polymorphisms of these genes and determine their association with clinical characteristics of patients with MD., Design: A case-control genetic association study was carried out, including 30 patients with definite Ménière's disease and 30 healthy controls. The coding regions of the target genes were amplified from blood samples by polymerase chain reaction (PCR), followed by direct sequencing. The associations of polymorphisms with clinical characteristics were analyzed with logistic regression., Results: Five polymorphisms were identified: rs426496 in AQP2; rs591810 in AQP3; and rs1805127, rs1805128, and rs17173510 in KCNE1. After adjustment, rs426496 was significantly associated with tinnitus during the initial crisis and with altered electronystagmography, and rs1805127 was significantly associated with nephropathy., Conclusions: The genetic variant rs426496 in AQP2; rs591810 in AQP3 and rs1805127, rs1805128, and rs17173510, in KCNE1 were found in patients with Ménière's disease. The polymorphism rs426496, in AQP2, is associated with tinnitus at the onset of Ménière's disease and altered electronystagmography. In addition, rs1805127, in KCNE1, is associated with the presence of nephropathy.

Purpose: Leber hereditary optic neuropathy (LHON) is a mitochondrial disease characterized by bilateral vision loss. More than 95% of LHON cases are associated with one of the three main mtDNA mutations: G11778A, T14484C, and G3460A. The other 5% of cases are due to other rare mutations related to the disease. The aim of this study was to identify the prevalence and spectrum of LHON mtDNA mutations, including the haplogroup, in a cohort of Brazilian patients with optic neuropathy and to evaluate the usefulness of iPLEX Gold/matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) technology in detecting LHON mutations., Methods: We analyzed a total of 101 patients; 67 had a clinical diagnosis of LHON and 34 had optic neuropathy of unknown etiology. Direct sequencing and iPLEX Gold/MALDI-TOF MS were used to screen for the most common pathogenic point mutations in LHON, together with the rare mutations G3733A, C4171A, T10663C, G14459A, C14482G, A14495G, C14568T, and C14482A., Results: We identified mutations in 36 patients, of whom 83.3% carried the G11778A mutation and 16.7% carried the T14484C mutation. In individuals with mutations, the haplogroups found were L1/L2, L3, C, R, U, D, and H. Rare mutations were not detected in any of the patients analyzed., Conclusions: The frequencies of the main LHON mutations were similar to those previously reported for Latin America. A different frequency was found only for the A3460G mutation. The most frequent haplogroups identified were of African origin. The iPLEX Gold/MALDI-TOF MS technology proved to be highly accurate and efficient for screening mutations and identifying the haplogroups related to LHON. The MassArray platform, combined with other techniques, enabled definitive diagnosis of LHON in 36% (36/101) of the cases studied.

Auditory neuropathy is a type of hearing loss that constitutes a change in the conduct of the auditory stimulus by the involvement of inner hair cells or auditory nerve synapses. It is characterized by the absence or alteration of waves in the examination of brainstem auditory evoked potentials, with otoacoustic and/or cochlear microphonic issues. At present, four loci associated with non‑syndromic auditory neuropathy have been mapped: Autosomal recessive deafness‑9 [DFNB9; the otoferlin (OTOF) gene] and autosomal recessive deafness‑59 [DFNB59; the pejvakin (PJVK) gene], associated with autosomal recessive inheritance; the autosomal dominant auditory neuropathy gene [AUNA1; the diaphanous‑3 (DIAPH3) gene]; and AUNX1, linked to chromosome X. Furthermore, mutations of connexin 26 [the gap junction β2 (GJB2) gene] have also been associated with the disease. OTOF gene mutations exert a significant role in auditory neuropathy. In excess of 80 pathogenic mutations have been identified in individuals with non‑syndromic deafness in populations of different origins, with an emphasis on the p.Q829X mutation, which was found in ~3% of cases of deafness in the Spanish population. The identification of genetic alterations responsible for auditory neuropathy is one of the challenges contributing to understand the molecular bases of the different phenotypes of hearing loss. Thus, the present study aimed to investigate molecular changes in the OTOF gene in patients with auditory neuropathy, and to develop a DNA chip for the molecular diagnosis of auditory neuropathy using mass spectrometry for genotyping. Genetic alterations were investigated in 47 patients with hearing loss and clinical diagnosis of auditory neuropathy, and the c.35delG mutation in the GJB2 gene was identified in three homozygous patients, and the heterozygous parents of one of these cases. Additionally, OTOF gene mutations were tracked by complete sequencing of 48 exons, although these results are still preliminary. Studying the genetic basis of auditory neuropathy is of utmost importance for obtaining a differential diagnosis, developing more specific treatments and more accurate genetic counseling.

Introduction: Auditory neuropathy is a condition in which there is a change in the neuronal transmission of the auditory stimuli. Our objective was to describe the patients' series within the clinical spectrum of auditory neuropathy., Material and Methods: We designed a transversal, retrospective study, with a description of a consecutive case series. Auditory neuropathy was defined by the presence of acoustic otoemissions plus absent/abnormal auditory brainstem responses with cochlear microphonism., Results: 34 patients with bilateral hearing loss, 23 males and 11 females, were included in the study. Eighty percent of the cases had congenital onset of hearing loss. Acoustic otoemissions were absent in 67% of them. Cochlear microfonism was present in 79% of all cases. Prenatal, perinatal or ambiental factors were present in 35.2% of the cases., Discussion: Medical literature shows great variability in findings related to auditory neuropathy, both in its etiology and epidemiological data., Conclusion: Auditory neuropathy presents a broad spectrum of changes that may result from mild to severe changes in the functioning of the auditory pathway, and in our sample we observed that 80% of Auditory neuropathy have congenital onset of hearing loss and/or with cochlear microphonism identified. 91% of patients experience significant hearing impairment and 53% suffer from severe or profound deafness.

Background: Recent advances in molecular genetics have enabled to determine the genetic causes of non-syndromic hearing loss, and more than 100 genes have been related to the phenotype. Due to this extraordinary genetic heterogeneity, a large percentage of patients remain without any molecular diagnosis. This condition imply the need for new methodological strategies in order to detect a greater number of mutations in multiple genes. In this work, we optimized and tested a panel of 86 mutations in 17 different genes screened using a high-throughput genotyping technology to determine the molecular etiology of hearing loss., Methods: The technology used in this work was the MassARRAY iPLEX® platform. This technology uses silicon chips and DNA amplification products for accurate genotyping by mass spectrometry of previous reported mutations. The generated results were validated using conventional techniques, as direct sequencing, multiplex PCR and RFLP-PCR., Results: An initial genotyping of control subjects, showed failures in 20 % of the selected alterations. To optimize these results, the failed tests were re-designed and new primers were synthesized. Then, the specificity and sensitivity of the panel demonstrated values above 97 %. Additionally, a group of 180 individuals with NSHL without a molecular diagnosis was screened to test the diagnostic value of our panel, and mutations were identified in 30 % of the cases. In 20 % of the individuals, it was possible to explain the etiology of the HL. Mutations in GJB2 gene were the most prevalent, followed by other mutations in in SLC26A4, CDH23, MT-RNR1, MYO15A, and OTOF genes., Conclusions: The MassARRAY technology has the potential for high-throughput identification of genetic variations. However, we demonstrated that optimization is required to increase the genotyping success and accuracy. The developed panel proved to be efficient and cost-effective, being suitable for applications involving the molecular diagnosis of hearing loss.

Background: Hearing loss is the most common sensory deficit in humans, affecting approximately 10% of the global population. In developed countries, one in every 500 individuals suffers from severe to profound bilateral sensorineural hearing loss. For those up to 5 years old, the proportion is higher, at 2.7 in 1000 individuals, and for adolescents the average is 3.5 in 1000. Among the causes of hearing loss, more than 50% are related to genetic factors. To date, nearly 150 loci and 64 genes have been associated with hearing loss. Mutations in the GJB2 gene, which encodes connexin 26, constitute the main genetic cause. So far, more than 300 variations have been described in this gene.As a response to the clinical and genetic heterogeneity of hearing loss and the importance of correct molecular diagnosis of individuals with hereditary hearing loss, this study worked in the optimization for a diagnostic protocol employing a high-throughput genotyping technology., Methods: For this work, was used the TaqMan® OpenArray™ Genotyping platform. This is a high performance, high-throughput technology based on real-time PCR, which enables the evaluation of up to 3072 SNPs (Single Nucleotide Polymorphisms), point mutations, small deletions, and insertions, using a single genotyping plate. For the study, were selected the layout allowing to analyze 32 alterations in 96 individuals simultaneously. In the end, the generated results were validated by conventional techniques, as direct sequencing, Multiplex PCR and RFLP-PCR., Results: A total of 376 individuals were analyzed, of which 94 were healthy controls, totaling 4 plates in duplicate. All 31 of the changes analyzed were present in the nuclear genes GJB2, GJB6, CRYL1, TMC1, SLC26A4, miR-96, and OTOF, and in the mitochondrial genes MT-RNR1 and MT-TS1. The reactions were subsequently validated by established techniques (direct sequencing, multiplex PCR, and RFLP-PCR) that had previously been used to perform molecular screening of hearing loss at the Human Genetics Laboratory of the Center for Molecular Biology and Genetic Engineering (CBMEG), at the State University of Campinas (UNICAMP). In total, 11,656 genotyping reactions were performed. Of these, only 351 reactions failed, representing approximately 3.01% of the total. The average accuracy of genotyping using the OpenArray™ plates was 96.99%., Conclusions: The results demonstrated the accuracy, low cost, and good reproducibility of the technique, indicating that the TaqMan® OpenArray™ Genotyping Platform is a useful and reliable tool for application in molecular diagnostic testing of hearing loss.

Mutations in the genes coding for connexin 26 (Cx26), connexin 30 (Cx30), and connexin 31 (Cx31) are the main cause of autosomal recessive nonsyndromic sensorineural hearing loss (AR-NSNHL). The 35delG mutation is the most frequent in the majority of Caucasian populations and may account for up to 70% of all GJB2 mutations. As a large number of affected individuals (10%-40%) with GJB2 mutations carry only one mutant allele, it has been postulated that the presence of additional mutations in the GJB6 gene (Cx30) explains the deafness condition found in these patients. In the present study, we screened the c.35delG mutation in ~600 unrelated Brazilian patients, with moderate to profound AR-NSNHL. Other point mutations in the coding region of the GJB2 gene were screened by sequencing analysis as well as the IVS 1+1 G>A splice site mutation in the same gene. Digenic mutations including large deletions and duplications were investigated in the Cx26, 30, and 31 genes in monoallelic individuals for mutations in the GJB2 gene. Large deletions and duplications were assessed by multiplex ligation-dependent probe amplification. We found 46 patients with mutations in only one GJB2 allele. Different pathogenic mutations associated with c.35delG were found in 13 patients. Two patients were identified with digenic heterozygous mutations. Our findings contributed to more accurate diagnosis and more appropriate genetic counseling in 28% of patients studied (13/46).

Purpose: There are many similarities in the clinical presentation of Leber hereditary optic neuropathy (LHON) and in patients who have optic neuropathy and a history of heavy tobacco and alcohol consumption. The main objective of this study is to investigate the frequency of primary and secondary mitochondrial DNA (mtDNA) mutations for LHON in patients diagnosed as having alcohol and tobacco optic neuropathy (ATON)., Methods: Twenty-six patients who had a history of heavy alcohol and tobacco consumption and who developed bilateral optic neuropathy were tested for primary mutations (G11778A, T14484C, and G3460A) by restriction analysis, and 14 secondary mutations in the genes mitochondrially encoded NADH dehydrogenase 1 (MT-ND1), mitochondrially encoded NADH dehydrogenase 4 (MT-ND4), mitochondrially encoded NADH dehydrogenase 4L (MT-ND4L), mitochondrially encoded NADH dehydrogenase 5 (MT-ND5), mitochondrially encoded NADH dehydrogenase 6 (MT-ND6), and mitochondrially encoded cytochrome B (MT-CYB) by direct sequencing., Results: Four (15.4%) of 26 patients tested positive for LHON primary mutations, two for the G11778A mutation, and two for the T14484C mutation. No patient tested positive for any of the 14 secondary mutations. Familial recurrence was present in four patients, and only three of these patients have presented the LHON mutation., Conclusions: The diagnosis of LHON should be considered in all patients diagnosed as having optic neuropathy, particularly those with familial recurrence of vision loss.

Mutations in GJB2 gene are the most common cause of nonsyndromic sensorineural recessive hearing loss. One specific mutation, c.35delG, is the most frequent in the majority of Caucasian populations and may account for up to 70% of all GJB2 mutations. However, 10-40% of the patients carry only one pathogenic mutation in the GJB2 gene. Deletions del(GJB6-D13S1830) and del(GJB6-D13S1854), truncating the GJB6 gene, have been detected in GJB2 heterozygous patients in different populations. The IVS 1+1 G>A splice site mutation in the noncoding region of the GJB2 gene has been found in heterozygous state in addition to c.35delG mutation. This mutation has not been reported in Brazilian deaf patients. In the present study we investigated the presence of the IVS 1+1 G>A mutation by multiplex ligation-dependent probe amplification in 185 unrelated Brazilian patients with autosomal recessive nonsyndromic sensorineural hearing loss (43 heterozygous patients and 142 without any pathogenic mutation in the GJB2-coding region). We have found two patients (4.6%) carrying the IVS 1+1 G>A mutation in compound heterozygous with c.35delG mutation.