The constantly evolving spectrum of phenotypes in titinopathies : will it ever stop?

PURPOSE OF REVIEW: The last few years have confirmed previous assumptions of an enormous impact of the titin gene (TTN) on the occurrence of muscle disease, cardiomyopathy, or both together. The reason for this rather late understanding of its importance is because of the huge size which prevented sequencing of the whole gene by the previous Sanger technique in the individual cases. An update of the advances in diagnosing titinopathies is the main focus of this review. RECENT FINDINGS: High throughput methods are now widely available for TTN sequencing and a corresponding explosion of different types of identified titinopathies is observed and published in the literature, although final confirmation is lacking in many cases with recessive missense variants. SUMMARY: The implications of these findings for clinical practice are easy to understand: patients with previously undiagnosed muscle disease can now have a correct diagnosis and subsequently receive a likely prognosis, can have accurate genetic counseling for the whole family and early treatment for predictable complications from the heart and respiratory muscles. In addition not to forget, they can avoid wrong diagnoses leading to wrong treatments.