In addition, mutations in six genes linked to telomere function have been found in familial IPF (telomerase reverse transcriptase, TERT [27,28]; telomerase RNA component, TR [27,28]; dyskerin, DKC1 [29]; telomere interacting factor 2, TINF2 [30]; regulator of telomere elongation helicase, RTEL1 [31]; and poly(A)-specific ribonuclease deadenylation nuclease, PARN [31]), which implicate telomere shortening and DNA-damage responses in IPF pathogenesis and which are also strongly suggested to induce AECII apoptosis [27,28,29,31]. Here, RTEL1 is linked to idiopathic pulmonary fibrosis.