Functional assessment tools in children with Pompe disease: A pilot comparative study to identify suitable outcome measures for the standard of care

Background: Pompe disease (PD) is a rare condition caused by mutations in gene encoding for the enzyme alpha-glucosidase, resulting in an abnormal intracellular accumulation of glycogen. The disease clinical spectrum ranges from severe infantile forms to adult-onset forms with minor limitations. Since 2000 enzyme replacement therapy (ERT) is available and disease natural history has changed, with prolonged survival and evidence of myopathic features. Methods: In this study, we monitored disease progression up to three years in eight young patients with PD. Based on the literature data and the long term personal experience, we selected validated functional scales for neuromuscular disorders and compared the results to identify a simple and reliable protocol for the follow-up of children with PD. Moreover, we evaluated cognitive functions using developmental/cognitive tests. Results: Based on study results, we suggest that motor functions in children with PD could be better assessed by Chop Intend, MFM20 (Motor Function Measure Scale for Neuromuscular Diseases 20) and NSAA (North Star Ambulatory Assessment), according to age and functional level. Evaluation should be completed with ROM (Range Of Motion) measurement, MRC (Medical Research Council) evaluation and 6MWT (6 Minute Walk test) when possible. Conclusions: The proposed protocol seems to be reliable and should be done every six months, because of the progressive natural history of the disease, the rapid changes typical of developmental age and the need to document ERT effects. About cognitive functions, additional tests to classical intelligence scales (WISC, WPPSI) should be useful to better describe specific neuropsychological profile.