Our study elucidated the molecular pathology of TTN variants in Slovenian patients with cardiomyopathy and presented the clinical manifestation of the recurrently identified TTN:c.12478del, moreover, it contributes to the understanding of the genetic background in this geographical region and highlights the importance of screening for rare TTNtv-s in the constitutively expressed exons of the I-band of the gene TTN in patients with DCM. The gene discussed is TTN; the disease is familial dilated cardiomyopathy.