Objective: To report a case of nonidentical twins affected with a congenital form of Steinert's myotonic dystrophy (DM1), conceived by IVF owing to parental sterility, in which the mother presented a paucisymptomatic form of DM1 which was diagnosed as a result of the condition inherited by the twins.
Design: Case report.
Setting: Neonatal intensive care unit of a tertiary hospital.
Patient(s): Newborn twins affected with the congenital form of DM1 and a 35-year-old nulliparous mother.
Intervention(s): In vitro fertilization.
Main outcome measure(s): Molecular study of the CTG triplet expansion related with DM1.
Result(s): Molecular study evidenced a pathologic expansion in both twins as well as in their mother.
Conclusion(s): This case should serve as a reminder to practitioners that assisted reproductive techniques have opened the possibility that asymptomatic or paucisymptomatic carriers of a genetic syndrome can inadvertently conceive fetuses affected with more serious forms of the illness.