Renal dysfunction can be a common complication in patients with myotonic dystrophy 1

• Age and sex were correlated to cystatin C even in neuromuscular patients.
• DM1 patients had elevated cystatin C, implying disease-specific mechanisms.
• Cystatin C was not elevated in patients with dystrophinopathy when compared by sex.
• A cardiorenal association was suggested in dystrophinopathy and DM1.

Although renal failure can be a life-threatening complication even in neuromuscular disorders (NMDs), renal dysfunction is easily overlooked because muscle atrophy decreases the serum creatinine level. Renal function was retrospectively assessed using cystatin C (CysC) in various NMDs to clarify the differences among diseases. As is in the general population, age was correlated to CysC, and female patients showed lower CysC levels. Although elevated CysC was frequent in myotonic dystrophy 1 (DM1: MIM 160900) and motor neuron disorders, an inter-disease comparison by sex adjusted for age showed that only DM1 had a higher CysC compared to other diseases. Multivariate linear regression with the stepwise method also suggested that the number of CTG repeats had an impact on CysC levels. In two autopsy DM1 cases, nephrosclerotic changes were observed even though they were in their forties. These facts suggested a disease-specific pathomechanism for renal dysfunction in DM1. Although further study is required, renal function should be carefully monitored in patients with DM1.