Bioimpedance phase angle as a prognostic tool in late-onset pompe disease: a single-centre prospective study with a 15-year follow-up

We reported the long-term follow-up of a population of Late onset Pompe disease treated with enzyme replacement therapy. Among predictors of treatment effectiveness and prognosis, we include body composition assessment by bioelectrical vectorial impedance.

Methods. In this single Centre, prospective study, we evaluate the response to enzyme replacement therapy in 15 patients (7 males) with LOPD in different stages of disease, aged 49.4+16.1, followed-up for 15 years. Treatment response was measured by the six-minute walking test, vital capacity in supine and upright position, respiratory muscle strength, muscle MRI, manual muscle testing. We investigated the usefulness of Body Impedance Vectorial Analysis for serial body composition assessment.

Results (in brief). Although most patients with LOPD benefit from long-term treatment, some secondary decline may occur after the first 3-5 years. Some nutritional (lower body mass index, higher fat free mass, higher phase angle) and disease parameters (higher creatinine and shorter disease duration at the beginning of treatment) seem to predict a better motor outcome. Lower Phase Angle may reflect loss of integrity of skeletal muscle membranes, resulting from lysosomal and autophagosomal dysregulation; this leads to treatment mis-targeting, and thus to worse treatment response, and ultimately to whole cell damage. Indeed, the muscle is one of the tissue with the highest rate of autophagosome formation and degradation.