Our data presented here revealed an intraindividual filamin C ratio below 4 (range 1.1–3.9) in all 15 myotilinopathy patients indicating that the filamin C ratio is also suited for differentiation of filaminopathy from myotilinopathy (sensitivity of this diagnostic marker to detect filaminopathy in our MFM cohort 100 %, specificity 100 %). This evidence concerns the gene FLNC and myofibrillar myopathy 5.