[DIAGNOSIS OF GENETIC VARIANT CARRIERS IN A PATIENT WITH ASYMPTOMATIC BIRT-HOGG-DUBÉ SYNDROME: A CASE REPORT].

Birt-Hogg-Dubé (BHD) syndrome is an autosomal dominant disorder caused by germline mutations in the folliculin gene (FLCN). It is characterized by skin tumors, multiple lung cysts, and renal tumors. Active genetic testing and appropriate periodic examinations of family lines of patients with BHD syndrome have not been widely performed. In this report, we present our experience regarding the diagnosis of asymptomatic family members with BHD syndrome. The proband was a 65-year-old female with a family history of colorectal cancer and spontaneous pneumothorax that affected her father. Computed tomography revealed an approximately 10 cm-sized tumor protruding from the upper pole of the left kidney, a buried tumor approximately 1.5 cm in length in the right kidney, and multiple pulmonary cysts. The patient underwent laparoscopic radical left nephrectomy. Pathological examination indicated that the resected tumor was a chromophobe renal cell carcinoma. After the surgery, there was no evidence of local recurrence or metastasis. The size of the tumor in the right kidney was monitored, but it did not increase. On FLCN genetic examination, targeted next generation sequencing revealed a partial deletion of exon 14, thus confirming the diagnosis of the patient to be BHD syndrome that caused the previously unreported pathogenic variant. Three years after the surgery, we conducted genetic counseling for the proposita and her three children. Genetic examination, performed at the request of the second daughter, confirmed that she carried the same genetic variant as her mother. This diagnosis prompted the second daughter to begin managing her health via periodic imaging tests.