A 37-year-old man presented with an asymptomatic right renal mass detected by ultrasonography and CT (Fig. a). No apparent cutaneous lesions were found by careful inspection and palpation of the skin. The patient had a history of spontaneous pneumothorax on both sides and underwent pulmonary bullectomy on the right side at the age of 30. His father had a history of recurrent spontaneous pneumothorax starting at the age of 28 and died of stoke at the age of 63. His uncle had a history of recurrent spontaneous pneumothorax starting at the age of 24 and died of an accident at the age of 56. Open partial nephrectomy was performed on the patient. Histopathologic examination revealed that the tumor was chromophobe RCC, nuclear grade G2, and 2.2 cm × 2.0 cm × 2.0 cm in size (Fig. b).\nGenomic DNA was extracted from blood samples collected from the patient and his family members. Mutation examination revealed that the proband carried a deletion of three bases (CCT) at nucleotides c.770-772 in exon 7 (c.770-772delCCT) (Fig. c), resulting in deletion of the 257th serine residue (p.257delS). No FLCN mutations were found in any other members of the patient’s family.
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).