CYP26B1 and allergic disease: The fact that CYP26B1 is regulated by and metabolises all-trans-retinoic acid (atRA) and our previous results, i.e. 1) being the top gene with largest average log2 FC, 2) having stable, sex- and allergy-independent expression change and 3) showing no underlying SNP hits indicated that retinoic acid-related pathways may be involved in MO.