Editors' Note: Prospective Natural History Study in 24 Adult Patients With LGMDR12 Over 2 Years of Follow-up: Quantitative MRI and Clinical Outcome Measures

De Wel et al. prospectively studied 24 patients with autosomal recessive limb-girdle muscular dystrophy type 12 (LGMDR12). Patients with LGMDR12 had no appreciable clinical worsening over a 2-year period according to repeated standardized clinical assessments, such as the 6-minute walk distance, 10-meter walk test, or Medical Research Council sum scores of muscle power. However, for patients with LGMDR12 and intermediate-stage fatty replacement of muscle tissue (20%–70% proton density fat fraction), there was a significant worsening of Biodex Isometric Dynamometry even after 1 year. The investigators conclude this quantitative tool may be useful in monitoring clinical progression and response to targeted treatments for LGMDR12. Dr. Kawada expresses a concern regarding lead-time bias in the cohort (unclear time of disease onset in a recessive condition) which may have confounded any differences in the various qualitative and quantitative assessments over time. In response, the investigators confirmed that patients were included at the time of clinical symptom onset. Both investigators agree that sex-related differences in disease progression are less well understood, and additional studies are suggested to explore reasons for the variability in prognosis between sexes and age groups.