Myostatin and follistatin as monitoring and prognostic biomarkers in dysferlinopathy

•Myostatin is lower in non-ambulant than ambulant dysferlinopathy patients.•Myostatin concentration can predict loss of ambulation in dysferlinopathy.•Change in myostatin concentration did not correlate with change in motor function.•Use of myostatin as a surrogate for function needs confounding variable adjustment.•Endogenous inhibition by follistatin was not linked to slower disease progression.