Predictors of prognosis in type 1 myotonic dystrophy (DM1): longitudinal 18-years experience from a single center

Marco Mazzoli 1, Alessandra Ariatti 1, Gian Carlo Garuti 2, Virginia Agnoletto 3, Maurilio Genovese 4, Manuela Gozzi 5, Shaniko Kaleci 6, Alessandro Marchioni 7, Marcella Malagoli 4, Giuliana Galassi 1

1 Department of Biomedical, Metabolic and Neural Sciences, University Hospitals of Modena, Italy; 2 Respiratory Unit, Mirandola Hospital, Italy; 3 Cardiology Unit, University Hospitals of Modena, Italy; 4 Neuroradiology Unit, University Hospitals of Modena, Italy; 5 Radiology Unit, University Hospitals of Modena, Italy; 6 Department of Surgical, Medical, Dental and Morphological Science with Interest in Transplant, Oncological and Regenerative Medicine, University of Modena and Reggio Emilia, Italy; 7 Respiratory Diseases Unit, Department of Medical and Surgical Sciences, University Hospitals of Modena, Italy

The aim of the study was to identify possible predictors of neurological worsening and need of non-invasive ventilation (NIV) in individuals affected by myotonic dystrophy type 1 (DM1), the most common form of adult-onset muscular dystrophy.

Methods. A retrospective observational cohort study was undertaken. Thirty-three patients with genetic diagnosis of DM1 were followed at our Neuromuscular unit in Modena. Abnormal trinucleotide repeat (CTG) expansion of dystrophy protein kinase gene (MDPK) on chromosome 19q 13.3 was the prerequisite for inclusion. The number of CTG repeats was determined. All the participants were older than 14 at the time of enrolment, therefore they could be included into the juvenile or adult form of the disease. Participants were neurologically evaluated every 6-8 months up to 18 years. Neurological impairment was assessed by Muscular Impairment Rating (MIRS), Medical Research Council (MRC), and modified Rankin (mRS) scales. The independent variables considered for prognosis were age at first evaluation, duration of the disease, CTG repeat number, gender, and presence of cardiac and vascular morbidities. 

Male patients were 51.5% and female patients 48.5%. Sixteen patients were younger than the mean age of 30.1 years, while the remaining 17 were up to 65. Twelve subjects (36.4%) underwent NIV before the end of follow-up. Muscle force and disability scores showed statistically significant deterioration (p < 0.001) during follow-up. The worsening was significantly higher among patients carrying higher number of CTG repeats and of younger age. The presence of cardio-vascular involvement has significant impact on neurological and respiratory progression.

Neurological worsening is predicted by CTG expansion size, young age and presence of cardio-vascular morbidities.

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