Restrictive respiratory sindrome in DM2 patients

Objectives: Respiratory involvement in myotonic dystrophy type 1 (DM1) is frequent. Respiratory insufficiency is, together with cardiac failure, the main cause of death in these patients. Reports on respiratory involvement in DM2 are limited. The aims of our study were to determine the frequency and severity of respiratory involvement and sleep apnoea in patients with DM2 compared to DM1. Methods: 20 patients with genetically determined DM2 (mean age 64.3 ± 8) and 40 patients with moderately severe age-matched DM1 (mean age 38.5 ± 11) were subjected to muscle strength assessment and: (1) subjective assessment of excessive daytime sleepiness (Epworth Sleepiness Scale-ESS); (2) spirometry and nocturnal polygraphy (PSG). Results: (1) 4 of 20 (20%) patients with DM2 and 12 of 40 (30%) patients with DM1 complained of daytime sleepiness; (2) 5 of 20 (25%) patients with DM2 and 14 patients with DM1 (35%) showed a restrictive respiratory impairment on respiratory function tests. Indication to nocturnal assisted ventilation (Bi-level) either due to nocturnal desaturation or sleep apnoeas was identified in 30% patients with DM1 subjected to PSG compared to 10% of patients with DM2 subjected to PSG. Conclusions: Although preliminary, our results indicate that respiratory involvement in DM2 is present and needs to be considered in patients with DM2 just like in DM1, because of the potentially treatable nature of the associated symptoms. Whether severity of respiratory involvement correlates with muscle impairment (MMRC) and disease duration needs to be further explored on a larger number of patients.