Familial analysis: pulmonary Birt-Hogg-Dubé syndrome in two siblings.

Birt-Hogg-Dubé syndrome (BHDS) is a rare autosomal dominant genetic disorder. This case report aims to increase awareness of pulmonary cystic lesions and BHDS in China by providing insights into the clinical features of this syndrome. We present two cases of BHDS from the same family. We describe their clinical presentations, imaging findings, genetic mutations and the disease within their family tree. Two confirmed BHDS patients, initially presented with recurrent pneumothorax. No concurrent skin cystic changes but multiple lung cysts and FLCN gene mutation were found. Additionally, they have a family history of pneumothorax. Colorectal lesions are also noticed in their family. Remarkably, the younger sister also carried a mutation in the MSH6 gene. For patients with lung cysts or pneumothorax on chest CT, it is advisable to trace the family history and remain vigilant for colorectal lesions.