A 54-year-old man was found to have asymptomatic, bilateral renal tumors by ultrasonography and computed tomography (CT) (Fig. a, b). CT scan also showed left pneumothorax (Fig. c). No apparent cutaneous lesions were found by careful inspection and palpation of the skin. The patient had a history of spontaneous pneumothorax at the age of 30. His son also had a history of spontaneous pneumothorax at the age of 17. Open bilateral and partial nephrectomies were performed. Histopathologic examination revealed that the tumor in the left kidney was chromophobe RCC, nuclear grade G2 (partial G1), and 1.7 cm × 1.5 cm × 1.5 cm in size (Fig. d); the tumor in the right kidney was clear-cell RCC, nuclear grade G2, and 5.0 cm × 4.7 cm × 4.5 cm in size (Fig. e).\nGenomic DNA was extracted from blood samples collected from the patient and his son. Mutation examination revealed that the proband and his son carried a deletion of two bases (AG) at nucleotides c.946-947 in exon 9 (c.946-947delAG) of the FLCN gene (Fig. f), which caused a frameshift mutation starting at the 316th amino acid (p.316fs388x). No RCC was detected by abdominal CT scan on the son.
The second patient was a 35-year-old male who presented with an asymptomatic right renal tumor. The presence of the tumor was revealed by ultrasound and CT examinations (fig. ). A laparoscopic right partial nephrectomy was performed, and the tumor was diagnosed as a chromophobe renal cell carcinoma (RC; fig. ). The carcinoma was negative for CD10, vimentin, and c-kit, and was partially positive for CK-7 (fig. ) and colloidal iron (fig. ). When the patient was 40 years of age, a CT examination revealed the presence of asymptomatic bilateral multiple PCs (fig. ). His mother, aunt, uncle, and grandfather all had histories of recurrent pneumothorax (fig. ). A few firm papules were also present on the patient's face (fig. ). The results of the skin biopsies revealed that the papules were FFs (fig. ) positive for factor 13a (fig. ) and c-kit (fig. ), and negative for CD34, α-SMA, S100, and CD68. Because the findings for this patient met 1 major criterion and 2 minor criteria [], he was diagnosed with BHD.