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Biomedical subjects

Thomas Balkany

Publications and source records attributed to Thomas Balkany.

7 recordsLinked to original sources
PubMed2005

Characterization of Usher syndrome type I gene mutations in an Usher syndrome patient population.

Usher syndrome type I (USH1), the most severe form of this syndrome, is characterized by profound congenital sensorineural deafness, vestibular dysfunction, and retinitis pigmentosa. At least seven USH1 loci, USH1A-G, have been mapped to the chromosome regions 14q32, 11q13.5, 11p15, 10q21-q22, 21q21, 10q21-q22, and 17q24-25, respectively. Mutations in five genes, including MYO7A, USH1C, CDH23, PCDH15 and SANS, have been shown to be the cause of Usher syndrome type 1B, type 1C, type 1D, type 1F and type 1G, respectively. In the present study, we carried out a systematic mutation screening of these genes in USH1 patients from USA and from UK. We identified a total of 27 different mutations; of these, 19 are novel, including nine missense, two nonsense, four deletions, one insertion and three splicing defects. Approximatelly 35-39% of the observed mutations involved the USH1B and USH1D genes, followed by 11% for USH1F and 7% for USH1C in non-Acadian alleles and 7% for USH1G. Two of the 12 MYO7A mutations, R666X and IVS40-1G > T accounted for 38% of the mutations at that locus. A 193delC mutation accounted for 26% of CDH23 (USH1D) mutations, confirming its high frequency. The most common PCDH15 (USH1F) mutation in this study, 5601-5603delAAC, accounts for 33% of mutant alleles. Interestingly, a novel SANS mutation, W38X, was observed only in the USA cohort. The present study suggests that mutations in MYO7A and CDH23 are the two major components of causes for USH1, while PCDH15, USH1C, and SANS are less frequent causes.

Abnormalities, Multiple↗
PubMed2005

Coenzyme Q-10 treatment of patients with a 7445A--->G mitochondrial DNA mutation stops the progression of hearing loss.

CONCLUSION: CoQ 10 may be helpful in delaying the progression of hearing loss in patients with the 7445A-->G mitochondrial mutation. Objective. To assess the effect of an antioxidant drug (Coenzyme Q-10) on the hearing level of patients with the mitochondrial DNA 7445A-->G mutation and associated sensorineural hearing loss (SNHL). Material and methods. We identified three patients with bilateral non-syndromic SNHL harboring the mitochondrial 7445A-->G mutation. Two patients had a family history of hearing loss with a strong matrilineal inheritance. The other patient did not have a family history of hearing loss. Two patients (1 with familial and 1 with sporadic SNHL) received treatment with 75 mg of Coenzyme Q-10 (CoQ10) twice a day for 1 year. The remaining patient with a familial form of hearing loss did not agree to take the treatment. Average bone conduction pure-tone thresholds for 0.5, 1, 2 and 4 kHz were obtained before and after diagnosis of mitochondrial hearing loss, and before and after treatment with CoQ10. Results. CoQ10-treated patients did not show any additional deterioration of their SNHL after 12 (familial case) and 13 months (sporadic case). The progression rate of SNHL was 6 dB/year in the 2 years prior to initiation of treatment in the familial case who received CoQ10 treatment. One year after being diagnosed with mitochondrial hearing loss, the patient who refused CoQ10 treatment exhibited an 11-dB deterioration of his hearing thresholds. There were no side-effects related to treatment with CoQ10.

Adult↗
PubMed2005

Audiological features of GJB2 (connexin 26) deafness.

OBJECTIVE: The aim of the present study was to characterize audiological profiles in patients with GJB2 deafness DESIGN: We screened DNA from 399 individuals with nonsyndromic deafness for mutations in the connexin 26 gene (GJB2) by sequence analysis. A total of 77 (19%) of these deaf individuals were biallelic GJB2 mutations (either homozygous or compound heterozygous mutations) (GJB2 deafness). Using the audiological classification criteria of genetic deafness proposed by the European Workshop on Genetic Hearing Loss, we analyzed audiograms of these patients to characterize audiological features of the GJB2 deafness. In addition, we reviewed audiological data of 411 deafness cases from the literature providing details of audiological data (including 157 with GJB2 deafness). RESULTS: All categories of hearing loss severity were found, with significant differences in the findings from GJB2 cases: 1 (4.5%) of 22 individuals with mild hearing loss, 10 (13.3%) of 75 with moderate loss, 14 (14.9%) of 94 with severe loss, and 52 (25%) of 208 with profound deafness (Chi-square test, 3 df, p = 0.016). 81.6% of patients with GJB2 mutations had severe to profound loss, 18.4% with mild to moderate loss (Chi-square test, p = 0.014). The 235delC mutation was always associated with profound deafness. The main audiogram shapes found were residual/sloping (72.7%) and flat (23.4%). There were no differences in the severity and audiogram shapes of the hearing impairment between homozygous and compound heterozygous GJB2 deafness (Chi-square test, p > 0.05). CONCLUSIONS: Our study shows that the probability of finding biallelic GJB2 mutations increases with the severity of hearing loss. Audiograms associated with GJB2 deafness were usually nonspecific. Patients with unknown causes of severe or profound hearing loss should be routinely tested for GJB2 mutations, but due to the variability in hearing loss, individuals with lesser degrees of hearing loss should not be precluded from testing.

Adolescent↗
PubMed2003

Cochlear implantation concurrent with translabyrinthine acoustic neuroma resection.

OBJECTIVES/HYPOTHESIS: Cochlear implants provide successful auditory rehabilitation for patients with profound sensorineural hearing loss who do not derive at least marginal benefit from conventional hearing aids. Patients with neurofibromatosis type 2 can present with bilateral profound sensorineural hearing loss caused by bilateral vestibular schwannomas. Auditory rehabilitation in these patients can be challenging. We present the case of one such patient who underwent a concurrent translabyrinthine vestibular schwannoma resection and cochlear implantation in the same ear. STUDY DESIGN: A case report and review of the literature. METHODS: Review the patient's medical record and MEDLINE literature search. RESULTS: The patient presented with a relatively small tumor that was situated in the fundus of the internal auditory canal with intralabyrinthine extension. Postoperative performance with implant stimulation was in the higher range of that for other cochlear implant patients. CONCLUSIONS: To the best of our knowledge, this is the first case reported of simultaneous cochlear implant and translabyrinthine acoustic neuroma resection in the same ear of a patient with neurofibromatosis type 2.

Auditory Threshold↗
PubMed2002

The prevalence of connexin 26 ( GJB2) mutations in the Chinese population.

Mutations in GJB2, encoding gap junction beta 2 protein (connexin 26), are responsible for the commonest form of non-syndromic recessive deafness in many populations. It has been reported recently that the most common 35delG mutation in GJB2 is exceptionally low in Japanese and Korean populations, but another deletion, 235delC, is relatively frequent. Since the Chinese constitute approximately one fifth of the global population, the frequency of GJB2 mutations in the population has important implications for understanding worldwide causes of genetic deafness. To determine whether GJB2 mutations are an important cause of deafness in Chinese, we conducted mutation screening for GJB2 in 118 deaf Chinese probands, including 60 from simplex and 58 from multiplex families with non-syndromic deafness, and 150 normal hearing Chinese controls. Four mutations, including 235delC, 299-300delAT, V37I, and 35delG, were found in the patients. Thirty-nine percent of the probands had a GJB2mutation. Of the 118 probands, 19 carried two definitely pathogenic mutations: three among the 58 multiplex cases (5.2%) and 16 among the 60 simplex cases (26.7%). Twenty-seven probands (22.9%) were found to carry only single GJB2 mutations. None of them had mutations in exon 1 of GJB2 and or the 342-kb deletion of GJB6. The 235delC mutation was the most prevalent mutation (20.3% of alleles), accounting for 81% of the pathologic alleles in multiplex cases and 67% in simplex cases. Analysis of the affected haplotypes in the patients with the homozygous 235delC mutation yielded evidence for a single origin of the mutation. The carrier frequency of the 235delC mutation in control subjects with normal hearing was 1.3%. The 35delG mutation was only noted as a heterozygous change in two simplex cases (1.2% of alleles). These results indicated that mutations in GJB2 are a major cause of inherited and sporadic congenital deafness in the Chinese population. The 235delC mutation, rather than 35delG, is the most common mutation found in the Chinese deaf population. Our data support the view that specific combinations of GJB2 mutation exist in different populations.

Alleles↗
PubMed2002

Mutations in the alternatively spliced exons of USH1C cause non-syndromic recessive deafness.

We have recently shown that USH1C underlies Usher syndrome type 1c (USH1C), an USH1 subtype characterized by profound deafness, retinitis pigmentosa, and vestibular dysfunction. USH1C encodes a PDZ-domain-containing protein, harmonin. Eight different Ush1c transcripts were identified in the mouse inner ear. Moreover, transcripts containing seven alternatively spliced exons (A-F, G/G) were found to be expressed in the inner ear, but not in the eye. These findings suggested that mutations involving USH1C might also be the cause of DFNB18, a form of non-syndromic deafness, which maps to a chromosomal region that includes USH1C. We screened 32 Chinese multiplex families with non-syndromic recessive deafness for USH1C mutations. In one family, congenital profound deafness without RP was associated with a C to G transversion in the alternatively spliced exon D, predicting an arginine to proline substitution at codon 608 in the proline-, serine- and threonine-rich region of harmonin. We also screened 320 deaf probands from other ethnic background and found three who were heterozygous for changes in the alternately spliced exons including Gly431Val in exon B, Arg620Leu and Arg636Cys in exon D. None of these mutations were detected in DNA from 200 control subjects with normal hearing including 110 Chinese. We also screened 121 non-Acadian probands with type 1 Usher syndrome. None carried any mutations in these exons of USH1C. Our findings show that USH1C mutations can also cause non-syndromic deafness and that some harmonin isoforms are specifically required for inner ear function.

Adaptor Proteins, Signal Transducing↗