Novel variants in Nordic patients referred for genetic testing of telomere-related disorders.

Telomere-related disorders are a clinically and genetically heterogeneous group of disorders characterized by premature telomere shortening and proliferative failure of a variety of tissues. This study reports the spectrum of telomere-related gene variants and telomere length in Nordic patients referred for genetic testing due to suspected telomere-related disorder. We performed Sanger sequencing of the genes TERT, TERC, DKC1, and TINF2 on 135 unrelated index patients and measured telomere length by qPCR on DNA from peripheral blood leukocytes. We identified pathogenic or likely pathogenic variants in 10 index patients, all of which had short telomeres compared to age-matched healthy controls. Six of the 10 variants were novel; three in TERC (n.69_74dupAGGCGC, n.122_125delGCGG, and n.407_408delinsAA) and three in TERT (p.(D684G), p.(R774*), and p.(*1133Wext*39)). The high proportion of novel variants identified in our study highlights the need for solid interpretation of new variants that may be detected. Measurement of telomere length is a useful approach for evaluating pathogenicity of genetic variants associated with telomere-related disorders.