What's in a name? That which we call IPF, by any other name would act the same.

Idiopathic pulmonary fibrosis (IPF) remains a truly idiopathic fibrotic disease, with a modest genetic predilection and candidate triggers but no overall explanation for the development of disease in non-familial cases. Agreement on terminology has contributed to major clinical and translational advances since the millennium. It is likely that the entity currently captured by the term "IPF" will be radically reclassified over the next decade, either through "splitting" (into IPF subgroups responding selectively to individual disease-modifying agents) or through "lumping" of IPF with other forms of progressive fibrotic lung disease (with shared pathogenetic mechanisms and IPF-like disease behaviour). In this perspective, we summarise the clinical and pathogenetic justification for a focus on "the progressive fibrotic phenotype" in future clinical and translational research. By this means, we can hope to address the needs of non-IPF patients with inexorably progressive fibrotic disease, currently disenfranchised by lack of access to agents that are efficacious in IPF. In this regard, ongoing trials of anti-fibrotic therapies in non-IPF patients with progressive fibrosis may be highly influential. Future revision of IPF nomenclature may be warranted if there are major conceptual changes but without compelling justification, the benefits of renaming IPF are likely to be outweighed by the resulting confusion.