FLCN and Birt-Hogg-Dubé syndrome: Birt-Hogg-Dubé (BHD) syndrome is a renal tumour predisposition syndrome, in which affected individuals develop a variety of histological types of renal tumours, pulmonary cysts and cutaneous fibrofolliculomas.1, 2, 3, 4 The folliculin (FLCN) gene, which is responsible for BHD syndrome, is a metabolic gene which regulates oxidative phosphorylation, amino acid sensing and kidney cell growth rate in collaboration with its interacting partners, folliculin-interacting proteins 1 (FNIP1) and 2 (FNIP2).5, 6, 7, 8, 9