No increase in the CTG repeat size during transmission from parent with expanded allele: false suspicion of contraction phenomenon

• Published in: Advances in laboratory medicine Vol. 4; no. 2; pp. 185 - 189
• Main Authors: Goñi Ros, Nuria, Sienes Bailo, Paula, González Tarancón, Ricardo, Martorell Sampol, Loreto, Izquierdo Álvarez, Silvia
• Format: Journal Article
• Language: English
• Published: Germany De Gruyter 12-06-2023
• Subjects: dmpk; myotonic dystrophy type 1; TP-PCR limitations; trinucleotide repeats; TP-PCR limitations; trinucleotide repeats; DMPK; myotonic dystrophy type 1
• ISSN: 2628-491X; 2628-491X
• DOI: 10.1515/almed-2022-0079

Myotonic dystrophy type 1 (DM1), also known as Steinert's disease, is a chronic, progressive and disabling multisystemic disorder with a broad spectrum of severity that arises from an autosomal-dominant expansion of the Cytosine-Thymine-Guanine (CTG) triplet repeat in the 3' untranslated region of the
gene (19q13.3).
In this study, we report the case of a family with several intergenerational expansions of the CTG repeat, with an additional case of a false suspicion of contraction phenomenon due to TP-PCR limitations.
The meiotic instability of the (CTG)
repeats leads to genetic anticipation where increased size of DM1 mutation and a more severe phenotype have been reported in affected individuals across generations. Even if extremely rare, a decrease in the CTG repeat size during transmission from parents to child can also occur, most frequently during paternal transmissions.