A novel FLCN gene mutation in a patient with bilateral renal tumors and no other clinical features of Birt Hogg Dubé syndrome. C.T. Dvorak^1,2, Y. Lien¹, G. Pridjian^1,2,3. 1) Human Genetics Program, Tulane Sch Medicine, New Orleans, LA; 2) Department of Pediatrics, Tulane Sch Medicine, New Orleans, LA; 3) Department of OB/GYN, Tulane Sch Medicine, New Orleans, LA.
   Birt Hogg Dubé Syndrome (BHD) was initially described as a genodermatosis syndrome in 1977, and since then a number of other clinical features (including renal tumors and spontaneous pneumothorax) have been observed in a portion of affected individuals. We describe a 46 year old female who presented with bilateral renal tumors of the chromophobe type. An analysis of the folliculin gene (FLCN) in peripheral blood lymphocytes revealed a novel frameshift mutation in exon 11 (c.1286dupA) that was similar in location and effect to previously described mutations in patients with BHD syndrome. However, our patient did not exhibit the commonly described skin findings or other phenotypic features of BHD, suggesting a greater degree of clinical variability than is typically described for the syndrome. We argue that BHD should be included (along with Von Hippel Lindau and other hereditary cancer syndromes involving the kidney) in the differential diagnosis of all patients presenting with bilateral renal tumors, even in the absence of other clinical findings. In addition, individuals considering FLCN mutation testing should be counselled regarding the variable expressivity and reduced penetrance that can be observed even among family members with BHD.