• pleural disease
• rare lung diseases

Individuals with pneumothoraces are frequently divided into young patients with the so-called primary spontaneous pneumothorax and older patients with lung disease causing secondary pneumothoraces. In truth, the younger patients may also have underlying lung disease either acquired through smoking, particularly cannabis, or inherited. Ten per cent of individuals presenting with apparently primary pneumothoraces will have a family history of pneumothorax, indicating a large heritable component.1 The most common genetic diagnosis in patients with familial pneumothoraces is Birt-Hogg-Dubé syndrome (BHD), an autosomal dominant condition caused by mutations of the FLCN gene encoding the protein folliculin. Two articles in this edition of Thorax address different aspect of BHD biology with potential implications for the diagnosis and management of these patients.2 3

Folliculin is so named because its deficiency can cause fibrofolliculomas to form. These hamartomas of the skin can aid diagnosis of BHD. Mutation of FLCN can also cause renal cell carcinomas to develop in up to a third of patients which if not treated early can be lethal. The diagnosis of BHD can often be made clinically based on a family history of pneumothoraces and/or renal cancer, dermatological examination revealing fibrofolliculomas and other skin lesions, and characteristic cross-sectional imaging of the thorax with predominantly basal cysts. Confirmation of the …