Skin lesions of Birt-Hogg-Dubé syndrome: clinical and histopathological findings in 31 Japanese patients who presented with pneumothorax and/or multiple lung cysts.

Birt-Hogg-Dubé syndrome (BHDS) typically involves fibrofolliculomas (FFs) and trichodiscomas (TDs) of the skin, multiple pulmonary cysts often with pneumothorax, and renal neoplasms [1–4]. Although the FLCN gene located in chromosome 17p11.2, when mutated, causes BHDS [5,6], its onset and conditions vary in each organ. Spontaneous pneumothorax usually develops in 20- to 40-year (yr)-olds, but in few patients over 40 [4], whereas skin lesions are commonly found in those over 25–35 yrs old and renal tumors appear in some over 40.