The diagnosis of BHDS is of critical importance in a patient presenting with kidney tumours since the management of these tumours is different from sporadic kidney tumours.31 Somatic BHD mutations or LOH at the BHD locus have been detected in 70% of RCCs from BHDS patients.24 The high frequency of second hits in BHD and bhd supports that it is a tumour suppressor gene. This evidence concerns the gene FLCN and kidney neoplasm.