Notably, only one individual in the case cohort carried both the SPDL1 minor allele and a qualifying variation in either RTEL1, PARN, TERC, or TERT, further suggesting that these are two independent mechanisms of IPF pathogenesis, and that mitotic spindle dysfunction pathway underlies a novel non-telomeric mechanism in IPF. This evidence concerns the gene RTEL1 and idiopathic pulmonary fibrosis.