* This is a 2 stage exploratory study with a 3-month observational phase on the natural course, followed by a 12-month, open-label, non-comparative, single-arm, phase II pilot study on the efficacy, safety and tolerability of a low-protein diet (LPD) in 8 adult patients with Bethlem myopathy (BM) and Ullrich congenital muscular dystrophy (UCMD). * Objective of this trial is to test the effect of a normocaloric LPD to reactivate autophagy in BM/UCMD patients. The primary end point of the study will be the change in muscle biopsy of Beclin 1, a marker of autophagy, at 1 year of LPD treatment when compared to baseline. * The rationale rests on our discoveries that (i) mitochondrial dysfunction mediated by inappropriate opening of the PTP plays a key role in collagen VI myopathies; (ii) defective autophagy with impaired removal of defective mitochondria amplifies the defect; and (iii) reactivation of autophagy with a low-protein diet or treatment with cyclosporine A, the mitochondrial PTP inhibitor, cured Co6a1-/- mice, hinting at a common target among all beneficial treatments - namely autophagy. * Specific aims of this project are to (i) study the modifications of clinical, nutritional and laboratory parameters in a cohort of patients with BM/UCMD during a 3-month observational period before starting the LPD treatment; (ii) assess the effect of a normocaloric LPD in correcting defective autophagy in muscle of patients; (iii) test if new non-invasive biomarkers of activation of autophagy examined in the blood are mirroring the effect of LPD in the muscle biopsy; (iv) assess the clinical efficacy and safety of the LPD with an innovative combination of complementary measures of the nutritional status in patients. * The anticipated output is defining and validating a therapeutic nutritional approach in autophagy upregulation for BM/UCMD.
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Reactivation of autophagy measured as a change in Beclin 1 as a marker of autophagy in muscle biopsy from baseline (Day 1) to Day 365
Timeframe: one year