A 54-year old man with asymptomtic, tiny, multiple, flesh-colored papules on both cheeks () was referred to us from the cardiothoracic surgery department, where he had been treated for recurrent pneumothorax of the left lung. He did not remember the onset of the lesions, but stated that the number was increasing. He had no special medical or family history. The papules were thought to be sebaceous hyperplasia or verruca plana and a punch biopsy was performed. The specimen showed an epithelial cord and fibrous stroma in the dermis and an anastomosing band from follicular epithelium (). A diagnosis of fibrofolliculoma was made, which is the major feature of BHDS.\nThere was no family history of the skin lesions, lung disease, and of benign or malignant tumors. Furthermore, multiple variable-sized lung cysts were found on his chest following computed tomographic scan and a right renal cyst 2 cm in diameter was found on abdominal sonography (). Molecular analysis of FLCN was performed after informed consent from the patient. Sequencing revealed a single nucleotide frameshift duplication occurring within the polycytosine tract located in exon 11, c.1285dupC (p.H429Pfs*27), resulting in a change of the 429th amino acid from histidine to proline in the FLCN gene product. Based on this, it is possible to accurately diagnose BHDS.\nHis pneumothorax was treated with thoracostomy and pleurodesis, and active treatment was not required for the skin lesions, lung cysts and renal cyst. He is on regular follow-up because renal and colorectal cancer can occur in this syndrome.
The first patient was a 37-year-old female who presented with an asymptomatic left renal tumor that was revealed by ultrasound and computed tomography (CT) examinations (fig. ). The CT examination also revealed the presence of asymptomatic bilateral multiple PCs (fig. ). Since the age of 35, a few firm papules had developed on her face and head (fig. ). The patient had no family history of pulmonary, renal, or cutaneous disease. A laparoscopic left nephrectomy was performed. On gross examination, the resected kidney was a yellowish, solid tumor with partial hemorrhage (fig. ). The tumor was identified as a clear cell renal carcinoma (fig. ) positive for vimentin stain (fig. ) and negative for CK-7. A skin biopsy of the papule on her head revealed it was a fibrofolliculoma (FF; fig. ) positive for factor 13a (fig. ) and c-kit (fig. ), and negative for CD34, α-smooth muscle actin (α-SMA), S100, and CD68. Because the findings for this patient met 1 major criterion and 2 minor criteria [], she was diagnosed with Birt-Hogg-Dubé syndrome (BHD).