GREM1 and sarcoidosis: Variations in certain genes, specifically those encoding gremlin for tissue repair (GREM1) (Heron et al., 2011), caspase recruitment domain-containing protein 15 (CARD15) - also referred to as nucleotide-binding oligomerization domain containing protein 2 (NOD2) (Sato et al., 2010), and the cytokine transforming growth factor (TGF) β3 (Kruit et al., 2006), increase susceptibility to fibrosis in sarcoidosis.