A Multicenter Retrospective Study in Turkish Children with Myotonic Dystrophy Type 1

Objectives: Myotonic dystrophy type 1 (DM1) is a multisystem disorder with a broad spectrum of severity caused by autosomal dominant inherited unstable expanded CTG repeat in the DMPK gene. DM1 is the most common type of adult-onset muscular dystrophy. In this study, it was aimed to investigate the genetic and clinical features of pediatric-onset cases, which are less common. Methods: Demographic, genetic and clinical data of the patients younger than 18 years with a genetically confirmed diagnosis, from nine centers in different geographical regions of Turkey were retrospectively investigated. Results: Twenty-six patients (mean age 11.9 years, 50% females, with 30.8% congenital, 53.8% pediatric, 15.4% juvenile form) were included. Antenatal history of polyhydramnios (7.7%), reduced fetal movements (26.9 %), low birth weight (15.3%), and prematurity (23.1%) were evident. Six patients needed mechanical ventilator care in the neonatal period. 22 patients had a family history of DM1 (13 maternal/ 9 paternal). The initial clinical manifestations were muscle weakness (53.9%), hypotonia (38.4%), myotonia (26.9%), developmental delay (23%), and abnormal gait (7.6%). Various findings showing multisystem involvement (3/26 cardiac dysrhythmia, 2/26 type 1 diabetes mellitus, 1/26 polycystic ovary syndrome, 12/26 psychiatric comorbidities (6/12 attention deficiency and hyperactivity), 6/25 gastrointestinal system findings, 3/25 abnormality in cranial magnetic resonance imaging) were detected. 15 patients were receiving carbamazepine and two mexiletine. 13 of them had partial treatment response. Conclusion: The genetic and clinical findings of pediatric DM1 patients are diverse, which requires a multi-faceted approach and management.