RAC1 and sarcoidosis: The specific human leukocyte antigen (HLA) class II haplotypes, innate immunity-related genes, regulators of calcium channels, G-protein-coupled receptors, the mammalian target of rapamycin (mTOR)-related pathways, the ras-related C3 botulinum toxin substrate 1 (Rac1) hubs, PTPRD, FAT atypical cadherins and KIF genes, regulator of migration and survival, are the most strongly associated genetic risk factor for sarcoidosis, supporting the opinion that sarcoidosis is an exposure-mediated immunologic disease [32,33,34].