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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., (Copyright © 2016 Elsevier B.V. All rights reserved.)

We made a cross-sectional study to analyze glucose intolerance of myotonic dystrophy type 1 (DM1) with several examination including oral glucose tolerance test (OGTT), insulin tolerance test (ITT) and adiponectin. Ninety-five DM1 patients participated in this study. Health examination data from general people were used as controls. In DM1, homeostasis model assessment-insulin resistance (HOMA-IR) was higher than control even in the lowest fasting blood sugar (FBS) stage (<80 mg/dl) and insulin sensitivity assessed by ITT was low regardless of their FBS. Insulinogenic index of DM1 was positively correlated to HOMA-IR. Insulinogenic index and sum of IRI in OGTT were markedly elevated in the lowest FBS stage and declined along with elevation of FBS. Consequently, as many as 13.3% of DM1 patients with 90-110 mg/dl of FBS exhibited DM pattern, while only 1.9% in control. Adiponectin was higher in DM1 than control. Although age correlated with adiponectin in both control and DM1, its impact was stronger in DM1. DM1 predisposes insulin resistance and compensatory hyperinsulinemia exist even in patients with low FBS. We should pay attention to glucose intolerance of DM1 patients earlier than that of the general population. It seemed that 90 mg/dl of FBS is an important index as an indication of careful managements.