Long-term Evaluation Parameters in GNE Myopathy: A Five-year Observational Follow-up Natural History Study

Abstract BackgroundA number of clinical trials targeting GNE myopathy patients have been conducted. However, useful clinical parameters for post-marketing surveillance and long-term clinical observation have not yet been established. ObjectiveWe 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. MethodsThirty-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-minute walk test, percent vital capacity and percent force vital capacity (%FVC), lean body mass (whole body, arms, and legs), creatine kinase (CK), Barthel Index, modified Rankin Scale, and SF-36 national standard scores were examined. ResultsOf 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=0.001), GMFM (p=0.001), grip power (p=0.013), pinch power (p<0.001), CK (p=0.030), %FVC (p<0.001), leg lean body mass (p=0.040), and the Physical Functioning subscale score of the SF-36 (p=0.015) at the 5th year evaluation relative to baseline. Among these parameters, summed MMT score, GMFM, pinch power, and %FVC showed significant changes even in non-ambulant patients.ConclusionsMMT, GMFM, pinch power, CK, %FVC, lean body mass, and Physical Functioning subscale score of the SF-36 are useful parameters for the long-term evaluation of GNE myopathy patients.