In five families without an identifiable FLCN mutation (BHD 2, 5, 9, 25 and 28) the clinical diagnosis BHD was based on histologically confirmed multiple fibrofolliculomas; in one of these kindreds both pneumothorax and renal cancer occurred (BHD 25, Table 5). Here, FLCN is linked to Birt-Hogg-Dube syndrome.