Background: Birt-Hogg- Dubé syndrome (BHDS) (MIM 135150) is an autosomal dominant predisposition to the development of follicular hamartomas (fibrofolliculomas), lung cysts, spontaneous pneumothorax, and kidney neoplasms. Germline mutations in BHD are associated with the susceptibility for BHDS. We previously described 51 BHDS families with BHD germline mutations.
Objective: To characterize the BHD mutation spectrum, novel mutations and new clinical features of one previously reported and 50 new families with BHDS.
Methods: Direct bidirectional DNA sequencing was used to screen for mutations in the BHD gene, and insertion and deletion mutations were confirmed by subcloning. We analyzed evolutionary conservation of folliculin by comparing human against the orthologous sequences.
Results: The BHD mutation detection rate was 88% (51/58). Of the 23 different germline mutations identified, 13 were novel consisting of: four splice site, three deletions, two insertions, two nonsense, one deletion/insertion and one missense mutation. We report the first germline missense mutation in BHD c.1978A>G (K508R) in a patient who presented with bilateral multifocal renal oncocytomas. This mutation occurs in a highly conserved amino acid in folliculin. Ten percent (5/51) of the families had individuals without histologically confirmed fibrofolliculomas. Of 44 families ascertained on the basis of skin lesions, 18 (41%) had kidney tumors. Patients with a germline BHD mutation and family history of kidney cancer had a statistically significantly increased probability of developing renal tumors compare to patients without a positive family history (p=0.0032). Similarly, patients with a BHD germline mutation and family history of spontaneous pneumothorax had a significant increased greater probability of having spontaneous pneumothorax than BHDS patients without a family history of spontaneous pneumothorax (p=0.011). A comprehensive review of published reports of cases with BHD germline mutation is discussed.
Conclusion: BHDS is characterized by a spectrum of mutations, and clinical heterogeneity both among and within families. Our findings support that BHDS is associated with a spectrum of cutaneous hamartomas ranging from fibrofolliculomas to perifollicular fibromas to angiofibroma.
- Birt-Hogg-Dube syndrome
- familial spontaneous pneumothorax
- renal neoplasms
- spontaneous pneumothorax
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