A primary cardiomyopathy has not yet been reported in patients with confirmed mutations in the SEPN or RYR1 genes; however, cores on muscle biopsy are non-specific and may be found as an additional feature in patients with primary cardiomyopathies due to mutations in the DES, TTN, LMNA and ACTA1 genes (see paragraph on differential diagnosis). This evidence concerns the gene TTN and cardiomyopathy.