Contribution of molecular analyses to the estimation of the risk of congenital myotonic dystrophy.
A molecular analysis of the maternal and child CTG repeat size and intergenerational amplification was performed in order to estimate the risk of having a child with congenital myotonic dystrophy (CMD). In a study of 124 affected mother-child pairs (42 mother-CMD and 82 mother-non-CMD) the mean maternal CTG allele in CMD cases was three times higher (700 repeats) than in non-CMD cases (236 repeats). When the maternal allele was in the 50-300 repeats range, 90% of children were non-CMD. In contrast, when the maternal allele was greater than 300 repeats, 59% inherited the congenital form. Furthermore, the risk of having a CMD child is also related to the intergenerational amplification, which was significantly greater in the mother-CMD pairs than in the mother-non-CMD pairs. Although the risk of giving birth to a CMD child always exists for affected mothers, our data show that such a risk is considerably higher if the maternal allele is greater than 300 repeats.
Cobo
A M
AM
Neurology Department, Hospital Ntra Sra de Aránzazu, Basque Country, Spain.
Poza
J J
JJ
Martorell
L
L
López de Munain
A
A
Emparanza
J I
JI
Baiget
M
M
D000328:Adult; D000483:Alleles; D002648:Child; D004247:DNA / Q000032:analysis*; D004587:Electrophoresis, Agar Gel; D005189:False Positive Reactions; D005260:Female; D005820:Genetic Testing; D006579:Heterozygote; D006801:Humans; D008297:Male; D018598:Minisatellite Repeats / Q000235:genetics*; D009223:Myotonic Dystrophy / Q000151:congenital* / Q000235:genetics*; D010375:Pedigree; D012306:Risk
D004247:DNA