Intergenerational Influence of Gender and the DM1 Phenotype of the Transmitting Parent in Korean Myotonic Dystrophy Type 1

Myotonic dystrophy type 1 (DM1) is the most common autosomal-dominant disorder caused by the CTG repeat expansion of the , and it has been categorized into three phenotypes: mild, classic, and congenital DM1. Here, we reviewed the intergenerational influence of gender and phenotype of the transmitting parent on the occurrence of Korean DM1. A total of 44 parent-child pairs matched for the gender of the transmitting parent and the affected child and 29 parent-child pairs matched for the gender and DM1 phenotype of the transmitting parent were reviewed. The CTG repeat size of the in the affected child was found to be significantly greater when transmitted by a female parent to a female child (DM1-FF) (median, 1309 repeats; range, 400-2083) than when transmitted by a male parent to a male child (650; 160-1030; = 0.038 and 0.048 using the Tukey HSD and the Bonferroni test) or by a male parent to a female child (480; 94-1140; = 0.003). The difference in the CTG repeat size of the between the transmitting parent and the affected child was also lower when transmitted from a male parent with classic DM1 (-235; -280 to 0) compared to when it was transmitted from a female parent with mild DM1 (866; 612-905; = 0.015 and 0.019) or from a female parent with classic DM1 (DM1-FC) (605; 10-1393; = 0.005). This study highlights that gender and the DM1 phenotype of the transmitting parent had an impact on the CTG repeat size of the in the affected child, with greater increases being inherited from the DM1-FF or DM1-FC situations in Korean DM1.