Long-term evaluation parameters in GNE myopathy: a 5-year observational follow-up natural history study

Background: A number of clinical trials targeting GNE myopathy patients have been conducted. However, useful clinical parameters for postmarketing surveillance and long-term clinical observation have not yet been established. Objective: We conducted a 5-year observational follow-up natural history study to identify evaluation parameters, which may be useful for the long-term observation of GNE myopathy patients. Methods: Thirty-three genetically confirmed GNE myopathy patients were recruited and evaluated at study entry (baseline) and yearly in a 5-year follow-up. Hand-held dynamometer measurements of knee extension strength, grip power and pinch power, summed Manual Muscle Testing (MMT) score of 17 muscles, Gross Motor Function Measure (GMFM), 6 min walk test, percent vital capacity and percent forced vital capacity (%FVC), lean body mass (whole body, arms and legs), creatine kinase, Barthel Index, modified Rankin Scale and 36-item Short Form Survey national standard scores were examined. Results: Of the 33 patients, 22 (66%) completed evaluations for the entire 5-year follow-up period. These patients had a significant reduction in summed MMT score (p=0.005), GMFM (p=0.005), pinch power (p<0.001) and %FVC (p<0.001) at the fifth year evaluation relative to baseline. Among these parameters, summed MMT score, GMFM, pinch power and %FVC showed significant changes even in non-ambulant patients. Conclusions: MMT, GMFM, pinch power and %FVC are useful parameters for the long-term evaluation of GNE myopathy patients.