Patients showed heterogeneity in muscle affectation and disability measured by different scales
Five clinically heterogeneous patients with DM1 were included in this study, whose age of onset ranged between 15 and 48 years. Their muscle dysfunction was studied using several different scales (Table 1 ). By using the mRS, we determined the degree of disability and/or dependence in the daily activities of these DM1 patients. In our cohort, P3 (with a mRS score of 1) had no significant disability and had no limitation in daily life activities despite the presented symptoms. Three patients, P1, P2 and P5 (mRS score of 2) presented with a slight disability, meaning they were unable to do activities they were able to in the past, but they remained independent. Moderate disease disability, (mRS score of 4) was found in P4, who was unable to walk and to attend to self-care. With regard to the MIRs scale, P3 showed minimal signs, P2 and P5 had distal weakness, and P1 and P4 mild-to-moderate proximal weakness. We also evaluated the same patients using the MRC scale, to measure strength in the biceps muscle (the muscle from which we obtained muscle cells). P2, P3 and P5 had preserved muscle strength (i.e. , MRC score = 5). Yet, P1 and P4 had an MRC of 4, indicating decreased muscle strength, a result consistent with the more proximal weakness that these two patients had when assessed with the MIRS scale. The same patients were submitted to a 6MWD test and P5 showed values within the normal range (Casanova et al., 2011). Values below the normal range were found for 6MWD in P1, P2 and P3. Although having better scores for mRS, MIRS and biceps MRC than P1, P2 walked 100 meters less. P4 was not able to perform the 6MWD test, since she was unable to walk. All scales showed heterogeneity among the patients in muscle function and degree of disability.