[Genetics of complex and syndromic palmoplantar keratoderma]

Palmoplantar keratodermas (PPK) comprise a heterogenous group of acquired and hereditary disorders marked by excessive thickening of the epidermis of palms and soles. Hereditary PPKs can be classified into 3 groups: 1) isolated non-syndromic PPKs; 2) complex non-syndromic PPKs associated with other ectodermal defects; and 3) syndromic PPKs associated with extracutaneous manifestations. All types of inheritance have been observed: autosomal dominant, autosomal recessive, X-linked recessive, and mitochondrial. Some of these disorders are restricted to geographic isolates. This review describes the different genetic causes of hereditary syndromic and complex PPKs for which the genes have been identified. The identification of pathogenic variants has consequences in terms of genetic counseling, appropriate medical care and follow-up, especially for PPKs predisposing to hearing loss, cardiomyopathies, benign tumors or carcinomas. In addition, the development of targeted therapies based on pathophysiology of disorders should allow a more effective treatment of these conditions in the near future.

Gap Junction Protein Beta 2 Gene Variants and Non-Syndromic Hearing Impairment among Couples Referred For Prenatal Diagnosis in the Northeast of Iran

INTRODUCTION

Hearing impairment is a complex medical disorder which has genetic and non-genetic causes. Gap Junction Protein Beta 2 (GJB2) gene variant is a well-known disease-causing gene among patients with hearing impairment. The frequencies of genetic variants in the GJB2 gene are different in each population. This study aimed to discuss the GJB2 gene status in an Iranian population with hearing impairment who referred for prenatal testing.

MATERIALS AND METHODS

This cross-sectional study was conducted in a genetic laboratory affiliated with Mashhad Jahad Daneshgahi, Mashhad, Iran. A total number of 21 bilateral hearing impaired patients were enrolled in this study. The exons for target GJB2 gene were amplified by polymerase chain reaction after the confirmation of the hearing impairment and the exclusion of the acquired causes of hearing loss.

RESULTS

The c.35delG and c.79G>A variants were the first and second most common variants in the study population, respectively. The mean age of the patients was 27.5 (8.7) years and 12 cases were male. There was no significant association between hearing impairment degree and age and heterozygosity status (P=0.376 and P=.074 respectively).

CONCLUSION

The c.35delG and c.79G>A variants were determined as the first and second most common variants in the GJB2 gene, respectively. The mean age of 26 years in this study population indicates the late referral for the evaluation of the hearing difficulty. Furthermore, it highlights the further need to encourage families with a history of hearing impairment to engage in genetic counseling.