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Introduction: 35delG mutation in GJB2 gene is the most frequent mutation in genetic hearing loss. The carrier screening for 35delG mutation to identify affected newborns is at the moment relatively inexpensive method for deafness diagnosis. The casual treatment of DFNB1 is impossible. Preimplantation genetic diagnosis (PGD) is a method allowing transfer mutation free embryos and successful pregnancies. It's an established procedure allowing genetic research of the oocyte before fertilization or embryo before implantation to the uterus., Aim: The aim of the present work was to perform PGD for GJB2 35delG mutation in a couple who had already a child affected with genetic hearing loss., Materials and Methods: The patient underwent a standard IVF procedure associated with intracytoplasmic sperm injection. 6–8 cell embryos were biopsied on day 3. Single cell nested PCR-RFLP protocol and sequence analysis for PGD was used for the detection of GJB2 35delG mutation., Results: In the course of IVF-PGD procedures, from 6 analyzed embryos 3 were predicted to be free of GJB2 35delG mutation in both alleles. Two embryos were heterozygous and one was affected for this mutation as homozygous mutation in both alleles. Of these, one healthy embryo was transferred, resulting in an unaffected singleton pregnancy., Conclusions: Preimplantation genetic diagnosis (PGD) of monogenic disorders is a very efficient method, especially for patients whose previous child is homozygous for genetic disorders. It offers new possibilities for the treatment for genetic disease carriers.

Unlabelled: The aim was to identify the frequency of different causes of congenital hearing loss and to investigate the age of treatment intervention., Material: 197 children with hearing loss, hospitalized in the Department of Infant Diseases between 2007-2009., Methods: Three-level audiological examinations, clinical investigations, specific tests for selected congenital infections and GJB2 mutations, neuroimaging., Results: In 14 children with negative screening test hearing loss was confirmed; in 14 with positive was excluded; in 5 newborns screening test was not performed. In 179/197 the confirmation of hearing impairment was obtained up to 6 months (90%). Sensorineural (176/197), bilateral (157/197) hearing loss dominated; conductive and mixed was in 21/197. In 97/176 children with sensorineural hearing loss, congenital CMV infection was confirmed; in 47/176 - GJB2 mutations; in 21 simultaneous CMV infection and GJB2 mutation; in 26 the reason was not identified. The hearing aids were applied in 128, in 76 up to 6 months; the cochlear implants received 36, mainly in the 1st. and 2nd. year of life. The improvement of hearing was obtained in 33., Conclusions: 1. Early identification of infants with hearing loss allows for an earlier introducing of comprehensive treatment and improvement of hearing. 2. The significant proportion of children with hearing loss in the course of congenital cytomegalovirus infection indicates the need to carry out tests to identify infection in newborns with abnormal hearing screening test. 3. Cochlear implants are now in Poland the standard method of treatment in partial and complete deafness in children, also the youngest.

Progress in the field of clinical and experimental electrophysiology helps us to elucidate connections between clinical problems and genetic cellular abnormalities. So far four genes have been discovered to be responsible for inherited forms of atrial fibrillation. Several polymorphisms in genes encoding angiotensinogen, connexin 40 and subunits of potassium channels (KCNE1) have been disclosed to correlate with this disease. On the other hand genetic background of preexcitation, atrio-ventricular nodal reentry tachycardia and ventricular tachycardias need further studies. More research is also needed to assess the efficacy of pharmacogenetic treatment methods for atrial fibrillation.

We present the results of complex clinical examination of children affected with sensorineural hearing loss. The siblings (minimum two) were born from unaffected parents and came from twelve families. Molecular studies confirmed genetic background of hearing loss in 6 families and enabled identification of GJB2 mutations in investigated probants.

Charcot-Marie-Tooth type X disease (CMTX) is the second most frequent inherited neuropathy, after CMT1A type associated with 17p11.2-p12 duplication. CMTX is inherited as X dominant trait and is caused by point mutations in Cx32 gene. In the study the first Polish group of 11 patients with CMTX from 4 families is presented. The following four mutations were found in Cx32 gene: Gly110Asp, Val 152 Asp, Arg 183 His and Glu 208 Gly. CMTX is characterized by X dominant trait of inheritance, a mild clinical course in affected females and slowly progressive atrophy and weakness of distal limb muscles. Both electrophysiological and sural nerve biopsy studies show axonal changes with secondary demyelination.

The GJB2 gene defects are the most frequent cause of autosomal recessive non-syndromic hearing loss (DFNB1). Epidemiological data suggest that 35delG is the most prevalent mutation found in 88% of mutated alleles. Another mutations - 313del14 was found in 7% of mutated alleles. The other mutations were identified only in single families. Following the analysis of distribution of GJB2 mutations in the Polish population we propose an algorithm for molecular diagnosis of DFNB1. We propose to screen all patients affected with prelingual non-syndromic deafness for 35delG mutation using ASO or multiplex AS-PCR methods. The presence of 35delG on two alleles confirms DFNB1. The identification of heterozygous 35delG mutation requires additional GJB2 analysis including 313del14 mutation detection and en exon 2 direct sequencing. To determinate the frequency of digenic (GJB2/GJB6) background of DFNB we screened 17 patients with heterozygous 35delG mutation for deletion of 342 kb in GJB6 gene. No such mutation was detected in the analyzed group.

Deafness is one of the most frequent congenital hearing impairments. Knowledge of its causes will result in elimination of risk factors and applying prophylactic activities. It is recognized that about 40% of hearing impairments have genetic origin and 80% of these are autosomal recessive. Introducing molecular diagnosis to medical practice makes precise identification of hearing impairment and genetic counseling possible. The authors present results of DNA examination in patients with hereditary deafness, performed at the National Research Institute of Mother and Child in Warsaw. Genetic cause of deafness was confirmed in 60% cases.

The aim of this study was to identify subjects with 35delG mutation of GJB2 gene as the most frequent genetic cause of deafness. Deaf patients receiving cochlear implantation at the ENT Clinic at University of Medical Sciences in Poznań and their family members were recruited to the study. Peripheral blood lymphocytes DNA was amplified in allele-specific PCR and analysed for single strand conformation polymorphism (SSCP) to detect mutation at DFNB1 locus. 35delG mutation at both alleles was found at 42.9% of deaf patients and 29.4% of health relatives were found to be carrier of the mutation at one allele. The study is thought to be a first step in analysis of typical mutations in Polish deaf population.