Mutations in a novel gene lead to kidney tumors, lung wall defects, and benign tumors of the hair follicle in patients with the Birt-Hogg-Dubé syndrome.

Birt-Hogg-Dubé (BHD) syndrome is a rare inherited genodermatosis characterized by hair follicle hamartomas, kidney tumors, and spontaneous pneumothorax. Recombination mapping in BHD families delineated the susceptibility locus to 700 kb on chromosome 17p11.2. Protein-truncating mutations were identified in a novel candidate gene in a panel of BHD families, with a 44% frequency of insertion/deletion mutations within a hypermutable C(8) tract. Tissue expression of the 3.8 kb transcript was widespread, including kidney, lung, and skin. The full-length BHD sequence predicted a novel protein, folliculin, that was highly conserved across species. Discovery of disease-causing mutations in BHD, a novel kidney cancer gene associated with renal oncocytoma or chromophobe renal cancer, will contribute to understanding the role of folliculin in pathways common to skin, lung, and kidney development.

Identification of the genes for kidney cancer: opportunity for disease-specific targeted therapeutics.

Recent advances in understanding the kidney cancer gene pathways has provided the foundation for the development of targeted therapeutic approaches for patients with this disease. Kidney cancer is not a single disease; it includes a number of different types of renal cancers, each with different histologic features, a different clinical course, a different response to therapy, and different genes causing the defects. Most of what is known about the genetic basis of kidney cancer has been learned from study of the inherited forms of kidney cancer: von Hippel Lindau (VHL gene), hereditary papillary renal carcinoma (c-Met gene), Birt Hogg Dubé (BHD gene), and hereditary leiomyomatosis renal cell cancer (fumarate hydratase gene). These Mendelian single-gene syndromes provide a unique opportunity to evaluate the effectiveness of agents that target the VHL, c-Met, BHD, and fumarate hydratase pathways.

Genotype-phenotype correlation in von Hippel-Lindau disease with retinal angiomatosis.

OBJECTIVES: To characterize the germline mutations found in a large population of persons having von Hippel-Lindau (VHL) disease mutations with the clinical characteristics of associated retinal capillary hemangioblastomas (RCHs), to measure the prevalence of RCHs among patients with VHL disease generally and specifically for each genotype category, to establish genotype-phenotype correlations between genotype category and phenotypic features of ocular VHL disease, and to establish genotype-phenotype correlations between genotype category and visual function. METHODS: Cross-sectional and molecular genetic study. Of 890 patients with VHL disease, 335 had ocular involvement in the form of RCHs. Statistical analysis was used to correlate the structure of the mutated VHL protein with the ocular phenotype. RESULTS: Three genotype categories (amino acid substitutions, protein-truncating mutations, and complete deletions of VHL protein) were defined in all patients. The prevalence of RCHs was lowest (14.5%) among patients with complete deletions; the overall prevalence of retinal angiomatosis was 37.2%. Genotype category had no correlation with the unilaterality or bilaterality of ocular disease or with the number or extent of peripheral RCHs. The prevalence of RCHs at the juxtapapillary location was lower among patients with protein-truncating mutations compared with those with amino acid substitutions. Complete deletions were associated with the highest mean visual acuity compared with the other 2 genotype categories. CONCLUSION: Patients with complete deletions of VHL protein have the lowest prevalence of ocular disease and the most favorable visual outcome. CLINICAL RELEVANCE: The VHL mutation genotype may be used to predict the prevalence and outcome of ocular VHL disease and to guide ophthalmic follow-up.

von Hippel-Lindau disease.

von Hippel-Lindau disease is a heritable multisystem cancer syndrome that is associated with a germline mutation of the VHL tumour suppressor gene on the short arm of chromosome 3. This disorder is not rare (about one in 36000 livebirths) and is inherited as a highly penetrant autosomal dominant trait (ie, with a high individual risk of disease). Affected individuals are at risk of developing various benign and malignant tumours of the central nervous system, kidneys, adrenal glands, pancreas, and reproductive adnexal organs. Because of the complexities associated with management of the various types of tumours in this disease, treatment is multidisciplinary. We present an overview of the clinical aspects, management, and treatment options for von Hippel-Lindau disease.

Tumors of the endolymphatic sac in patients with von Hippel-Lindau disease: implications for their natural history, diagnosis, and treatment.

OBJECT: Endolymphatic sac tumors (ELSTs), which often are associated with von Hippel-Lindau (VHL) disease, cause irreversible hearing loss and vestibulopathy. Clinical and imaging surveillance protocols provide new insights into the natural history, mechanisms of symptom formation, and indications for the treatment of ELSTs. To clarify the uncertainties associated with the pathophysiology and treatment of ELSTs, the authors describe a series of patients with VHL disease in whom serial examinations recorded the development of ELSTs. METHODS: Patients with VHL disease were included if serial clinical and imaging studies captured the development of ELSTs, and the patients underwent tumor resection. The patients' clinical, audiological, and imaging characteristics as well as their operative results were analyzed. Five consecutive patients (three men and two women) with a mean age at surgery of 34.8 years and a follow-up period of 6 to 18 months were included in this study. Audiovestibular symptoms were present in three patients before a tumor was evident on neuroimaging. Imaging evidence of an intralabyrinthine hemorrhage coincided with a loss of hearing in three patients. Successful resection of the ELSTs was accomplished by performing a retrolabyrinthine posterior petrosectomy (RLPP). Hearing stabilized and vestibular symptoms resolved after surgery in all patients. No patient has experienced a recurrence. CONCLUSIONS: Audiovestibular symptoms, including hearing loss, in patients with VHL disease can be the result of microscopic ELSTs. Once an ELST has been detected, it can be completely resected via an RLPP with preservation of hearing and amelioration of vestibular symptoms. Early detection and surgical treatment of small ELSTs, when hearing is still present, should reduce the incidence and severity of hearing loss, tinnitus, vertigo, and cranial nerve dysfunction, which are associated with these tumors.

Genetic basis of cancer of the kidney: disease-specific approaches to therapy.

Studies during the past two decades have shown that kidney cancer is not a single disease; it is made up of a number of different types of cancer that occur in this organ. Clear cell renal carcinoma is characterized by mutation of the VHL gene. The VHL gene product forms a heterotrimeric complex with elongin C, elongin B, and Cul-2 to target hypoxia-inducible factors 1 and 2alpha for ubiquitin-mediated degradation. VHL-/- clear cell renal carcinoma overexpresses epidermal growth factor receptor and transforming growth factor alpha. Both hypoxia-inducible factor 1alpha and the epidermal growth factor receptor are potential therapeutic targets in clear cell renal carcinoma. Studies of the hereditary form of renal cell carcinoma (RCC) associated with hereditary papillary renal carcinoma (HPRC) determined that the c-Met proto-oncogene on chromosome 7 is the gene for HPRC and for a number of sporadic papillary RCCs. The HPRC c-Met mutations are activating mutations in the tyrosine kinase domain of the gene. The gene for a new form of hereditary RCC (Birt Hogg Dubé syndrome) associated with cutaneous tumors, lung cysts, and colon polyps or cancer has recently been identified. Studies are currently under way to determine what type of gene BHD is and how damage to this gene leads to kidney cancer. Individuals affected with hereditary leiomyomatosis renal cell carcinoma are at risk for the development of cutaneous leiomyomas, uterine leiomyomas (fibroids), and type 2 papillary RCC. The HLRC gene has been found to be the Krebs cycle enzyme, fumarate hydratase. Studies are under way to understand the downstream pathway of this cancer gene.

Risk of renal and colonic neoplasms and spontaneous pneumothorax in the Birt-Hogg-Dubé syndrome.

The Birt-Hogg-Dubé syndrome, a genodermatosis characterized by benign tumors of the hair follicle, has been associated with renal and colonic neoplasms and spontaneous pneumothorax, but the risk of developing these disorders is unknown. We identified risk factors for renal tumors and spontaneous pneumothorax in 98 patients affected with the Birt-Hogg-Dubé syndrome, in 13 Birt-Hogg-Dubé haplotype carriers, and in 112 unaffected family members. Development of renal tumors was strongly associated with the Birt-Hogg-Dubé syndrome and age. The odds ratio for renal tumor in BHD-affected family members adjusted for age was 6.9 (95% confidence interval, 1.5-31.6) and approximately 9.0 for the other risk factors considered. Chromophobe renal carcinoma, an uncommon type of renal cancer, was the predominant type of renal cancer found. Spontaneous pneumothorax was also strongly associated with the Birt-Hogg-Dubé syndrome and age. The odds ratio for pneumothorax in BHD-affected individuals, adjusted for age, was 50.3 (95% confidence interval, 6.4-392), and about 32 times higher adjusting for the other risk variables. Colon cancer and colon polyps were not related to the Birt-Hogg-Dubé syndrome. The Birt-Hogg-Dubé syndrome confers an increased risk for the development of renal tumors and spontaneous pneumothorax. We found no increase in risk for the development of colon polyps or colon carcinomas.

The natural history of hemangioblastomas of the central nervous system in patients with von Hippel-Lindau disease.

OBJECT: The goals of this study were to define the natural history and growth pattern of hemangioblastomas of the central nervous system (CNS) that are associated with von Hippel-Lindau (VHL) disease and to correlate features of hemangioblastomas that are associated with the development of symptoms and the need for treatment. METHODS: The authors reviewed serial magnetic resonance images and clinical histories of 160 consecutive patients with VHL disease who harbored CNS hemangioblastomas and serially measured the volumes of tumors and associated cysts Six hundred fifty-five hemangioblastomas were identified in the cerebellum (250 tumors), brainstem (64 tumors, all of which were located in the posterior medulla oblongata), spinal cord (331 tumors, 96% of which were located in the posterior half of spinal cord), and the supratentorial brain (10 tumors). The symptoms were related to a mass effect. A serial increase in hemangioblastoma size was observed in cerebellar, brainstem, and spinal cord tumors as patients progressed from being asymptomatic to symptomatic and requiring surgery (p < 0.0001). Twenty-one (72%) of 29 symptom-producing cerebellar tumors had an associated cyst, whereas only 28 (13%) of 221 nonsymptomatic cerebellar tumors had tumor-associated cysts (p < 0.0001). Nine (75%) of 12 symptomatic brainstem tumors had associated cysts, compared with only four (8%) of 52 nonsymptomatic brainstem lesions (p < 0.0001). By the time the symptoms appeared and surgery was required, the cyst was larger than the causative tumor; cerebellar and brainstem cysts measured 34 and 19 times the size of their associated tumors at surgery, respectively. Ninety-five percent of symptom-producing spinal hemangioblastomas were associated with syringomyelia. The clinical circumstance was dynamic. Among the 88 patients who had undergone serial imaging for 6 months or longer (median 32 months), 164 (44%) of 373 hemangioblastomas and 37 (67%) of 55 tumor-associated cysts enlarged. No tumors or cysts spontaneously diminished in size. Symptomatic cerebellar and brainstem tumors grew at rates six and nine times greater, respectively, than asymptomatic tumors in the same regions. Cysts enlarged seven (cerebellum) and 15 (brainstem) times faster than the hemangioblastomas causing them. Hemangioblastomas frequently demonstrated a pattern of growth in which they would enlarge for a period of time (growth phase) and then stabilize in a period of arrested growth (quiescent phase). Of 69 patients with documented tumor growth, 18 (26%) harbored tumors with at least two growth phases. Of 160 patients with hemangioblastomas, 34 patients (median follow up 51 months) were found to have 115 new hemangioblastomas and 15 patients new tumor-associated cysts. CONCLUSION: In this study the authors define the natural history of CNS hemangioblastomas associated with VHL disease. Not only were cysts commonly associated with cerebellar, brainstem, and spinal hemangioblastomas, the pace of enlargement was much faster for cysts than for hemangioblastomas. By the time symptoms appeared, the majority of mass effect-producing symptoms derived from the cyst, rather than from the tumor causing the cyst. These tumors often have multiple periods of tumor growth separated by periods of arrested growth, and many untreated tumors may remain the same size for several years. These characteristics must be considered when determining the optimal timing of screening for individual patients and for evaluating the timing and results of treatment.

Endolymphatic sac tumors in von Hippel-Lindau disease.

OBJECT: Von Hippel-Lindau (VHL) disease is a hereditary multiple-neoplasia syndrome mapping to chromosome 3p25-26. Endolymphatic sac (ELS) tumors have been identified as a neoplastic manifestation of VHL disease. The purpose of this study was to evaluate comprehensively the natural history of inner ear disease in a large population of patients with confirmed or suspected VHL disease and to correlate the clinical features with the VHL genotype. METHODS: The authors collated and analyzed clinical and genotypic data obtained in patients enrolled in an Institutional Review Board-approved protocol in which families and individuals affected by VHL disease were studied. These data included results from multidisciplinary history workups and physical examinations, imaging studies, and a battery of audiological tests. One hundred seventy-five patients were enrolled in the study, 129 with confirmed VHL disease and 46 of their family members in whom test results for VHL disease were negative and who served as controls. Twenty-one patients had ELS tumors that were evident on magnetic resonance images; three of them had bilateral ELS lesions. Hearing loss, often sudden in onset and severe to profound in nature, vestibulopathy, aural fullness, and tinnitus represented the primary symptoms of ELS tumor. Distinct patterns of auditory and vestibular dysfunction occurred at different stages of the disease. Phenotypic data showed that 17 of 21 patients with ELS tumors did not have pheochromocytomas, whereas all had VHL disease affecting the kidney, all but two had VHL disease affecting the central nervous system, and all but one had disease affecting the pancreas. Genotyping revealed 10 rearrangements (partial deletions), eight single bp substitutions, and one 3-bp insertion. Although there was no difference in the incidence of hearing loss between populations, symptoms of imbalance and aural fullness were more common in patients with VHL disease but without imaging evidence of ELS tumor than they were in family members who did not have VHL disease (p < 0.01). CONCLUSIONS: Endolymphatic sac tumors are frequently associated with VHL disease. Symptoms of disequilibrium or aural fullness in patients with VHL disease may be an early indication of endolymphatic dysfunction. Patients with VHL disease provide a unique opportunity to examine the effects of specific gene mutations and a discrete neoplastic process on the human inner ear. The study of ELS tumors in this group also provides a pathological model of ELS function and supplies evidence for a role of the ELS in clinical Ménière-like disease(s).

Close ties: an exploratory Colored Eco-Genetic Relationship Map (CEGRM) study of social connections of men in Familial Testicular Cancer (FTC) families.

BACKGROUND: Testicular cancer, while rare compared with other adult solid tumors, is the most common cancer in young men in northern Europe and North America. Risk factors include white race, positive family history, contralateral testicular cancer, cryptorchidism, infertility and testicular microlithiasis. As the genetic causes of familial clusters (Familial Testicular Cancer or FTC) are being sought, it is also important to understand the psycho-social experiences of members of FTC families. METHODS: This is a cross-sectional examination via the Colored Eco-Genetic Relationship Map (CEGRM) of social connections reported by 49 men in FTC families participating in NCI research study 02-C-178. RESULTS: The CEGRM was acceptable and feasible for use with men in FTC families, and valuable in understanding their social connections. These men have largely adjusted to the TC history in themselves and/or their relatives. They have considerable social and emotional support from family and friends, although there is wide variability in sources and types. CONCLUSIONS: The CEGRM focuses on men's social connections and close emotional bonds in FTC families. This action-oriented process of placing colored symbols on significant relationships uncovered previously under-appreciated emotions accompanying men's social exchanges. Most men in FTC families succeed in re-establishing a sense of normalcy in their lives and social connections, in the aftermath of a testicular cancer diagnosis.

Association of germline mutations in the fumarate hydratase gene and uterine fibroids in women with hereditary leiomyomatosis and renal cell cancer.

OBJECTIVE: To investigate the risk of uterine fibroids and other reproductive risk factors in women with hereditary leiomyomatosis and renal cell cancer (HLRCC). DESIGN: Case-control study. SETTING: National Institutes of Health, Rockville, Maryland. Patients A family-based case-control study was conducted between July 1, 2004, and June 30, 2006, including 105 women from families with HLRCC ascertained throughout North America. A telephone interview was conducted with all participants using a standardized questionnaire that elicited information about their menstrual, pregnancy, uterine fibroid, and hormonal contraceptive use history. Diagnosis of uterine fibroids was confirmed by pathologic diagnosis and by medical record review. DNA was extracted from blood samples and was screened for germline mutations in the fumarate hydratase (FH) gene. MAIN OUTCOME MEASURES: FH germline mutation status, presence of uterine fibroids, age at diagnosis, and symptoms and treatment of uterine fibroids. RESULTS: Of 105 women, 77 reported a history of uterine fibroids. Regardless of uterine fibroid status, 75 of 105 women had a germline mutation in FH (FH(mut) positive). The risk of uterine fibroids in FH(mut)-positive women was statistically significantly increased compared with that in FH(mut)-negative women (odds ratio [OR], 7.6; 95% confidence interval [CI], 2.9-20.0), as it was among women clinically affected with HLRCC compared with those clinically unaffected with HLRCC (8.6; 3.1-24.0). The median age at uterine fibroid diagnosis for FH(mut)-positive women (28 years) was significantly younger than that for FH(mut)-negative women (38 years) (P =.03). Women with a germline mutation in FH or clinically affected with HLRCC reported younger age at menarche (P < .004) compared with FH(mut)-negative women (P = .02) or women who were clinically unaffected with HLRCC. Women with HLRCC were more likely to have had treatment for uterine fibroids (OR, 4.6; 95% CI, 1.4-15.8), including hysterectomy (P =.02) at an earlier age compared with women who were clinically unaffected with HLRCC. CONCLUSIONS: This study provides the first evidence (to our knowledge) that women with germline mutations in FH and with clinical HLRCC have an increased risk of developing uterine fibroids. These women also have a younger age at uterine fibroid diagnosis and are more likely to have treatment for uterine fibroids at a younger age than women without HLRCC in their families.

Familial renal carcinoma: clinical evaluation, clinical subtypes and risk of renal carcinoma development.

PURPOSE: Familial renal carcinoma is defined as families with 2 or more individuals with renal cell carcinoma without evidence of known hereditary renal carcinoma syndromes. To better characterize this familial cancer we reviewed renal carcinoma families evaluated at the National Cancer Institute between 1990 and 2004 to identify distinctive features of these families. We also determined the risk of renal carcinoma in first-degree relatives of affected family members. MATERIALS AND METHODS: We evaluated 141 at risk asymptomatic relatives of affected individuals from 50 families with 2 or more members with renal carcinoma. Histology slides of renal tumors from affected family members were reviewed. At risk members from renal carcinoma families were screened for occult renal neoplasms by renal ultrasound and computerized tomography. DNA from select families was tested for germline mutations of known renal carcinoma genes when clinically indicated and constitutional cytogenetic analysis was performed to search for germline chromosome alterations. RESULTS: Familial renal carcinoma families could be subdivided into subtypes based on tumor multiplicity and renal tumor histology. Of 141 at risk members of renal carcinoma families screened for occult renal tumors 2 were found to have occult renal tumors, which were identified as renal oncocytoma and a solid tumor that was not resected, respectively. No histologically confirmed occult renal carcinomas were detected in at risk family members. Several families previously classified as having familial renal carcinoma were found on further evaluation to have hereditary renal cancer syndromes. CONCLUSIONS: Familial renal carcinoma is a heterogeneous clinical and pathological entity. Familial renal carcinoma was subdivided into groups based on tumor multiplicity and tumor pathology. The empirical risk of histologically documented renal carcinoma in first-degree relatives who were members of familial renal carcinoma families was less than 1:141. One renal oncocytoma and 1 small solid renal tumor were detected.

Hereditary leiomyomatosis and renal cell cancer: a syndrome associated with an aggressive form of inherited renal cancer.

PURPOSE: Hereditary leiomyomatosis and renal cell cancer is a recently described hereditary cancer syndrome in which affected individuals are at risk for cutaneous and uterine leiomyomas, and kidney cancer. Our initial experience revealed the aggressive behavior of these renal tumors, often with early metastasis, despite small primary tumor size. We report the clinical characteristics and urological treatment of patients with hereditary leiomyomatosis and renal cell cancer associated renal tumors. MATERIALS AND METHODS: A total of 19 patients with hereditary leiomyomatosis and renal cell cancer associated renal tumors were evaluated. The 11 women and 8 men had a median age at diagnosis of 39 years (range 22 to 67), and a median clinical and radiological followup of 34 months (range 6 to 141). Hereditary leiomyomatosis and renal cell cancer manifestations in patients with renal tumors included cutaneous leiomyomas in 11 of 17 evaluable patients (65%) and uterine leiomyomas in 7 of 7 evaluable females (100%). RESULTS: Median pathological tumor size was 7.8 cm (range 1.5 to 20). Histological subtypes were consistent with hereditary leiomyomatosis and renal cell cancer renal carcinoma. Four of 7 patients with 2.0 to 6.7 cm T1 tumors had spread to regional lymph nodes or metastases at nephrectomy. Overall 9 of 19 patients (47%) presented with nodal or distant metastases. CONCLUSIONS: Renal tumors in patients with hereditary leiomyomatosis and renal cell cancer syndrome are significantly more aggressive than those in patients with other hereditary renal tumor syndromes. In contrast to other familial renal cancer syndromes, the observation of 3 cm or less renal tumors associated with hereditary leiomyomatosis and renal cell cancer is not recommended. Careful followup of affected and at risk individuals in families is necessary.

Clinical, genetic and radiographic analysis of 108 patients with von Hippel-Lindau disease (VHL) manifested by pancreatic neuroendocrine neoplasms (PNETs).

BACKGROUND: von Hippel-Lindau (vHL) disease is an autosomal dominant syndrome associated with neoplasms in multiple organs, which includes the pancreas. Here, we report the greatest single center experience in patients with vHL pancreatic endocrine neoplasm (PNETs). METHODS: Between December 1998 and November 2006, 633 patients with vHL were evaluated and those with PNETs were enrolled on a prospective protocol. RESULTS: Overall, 108 vHL patients had PNETs (17%). Nine patients had metastatic disease (8.3%) from their PNET. Patients with lesions greater than 3 cm (n = 25) were more likely to develop metastases than patients with lesions less than 3 cm (n = 83) (P < .005). Thirty-nine patients underwent resection. Germline sequencing showed that 78% of patients with metastases (7/9) had exon 3 mutations compared with 46% of patients without metastases (32/98; P < .01). Tumor doubling time was calculated for the largest PNET. The group with metastases had an average tumor doubling time of 337 days (range, 180-463 days) compared with 2630 days (range, 103-9614 days) for those without metastases (P < .0001). CONCLUSIONS: By implementing a system of selective operative resection based on defined criteria, vHL patients with PNETs can be managed safely. For patients with small primary lesions (<3 cm), without a mutation of exon 3 and slow tumor doubling time (>500 days), a nonoperative approach may be appropriate for these nonfunctional neoplasms.

Lung cysts, spontaneous pneumothorax, and genetic associations in 89 families with Birt-Hogg-Dubé syndrome.

RATIONALE: Birt-Hogg-Dubé syndrome (BHDS) is an autosomal, dominantly inherited genodermatosis that predisposes to fibrofolliculomas, kidney neoplasms, lung cysts, and spontaneous pneumothorax. OBJECTIVES: We evaluated 198 patients from 89 families with BHDS to characterize the risk factors for pneumothorax and genotype-pulmonary associations. METHODS: Helical computed tomography scans of the chest were used to screen for pulmonary abnormalities. BHD mutation data were used for genotype-pulmonary associations. We examined the relationship of pneumothorax with categorical parameters (sex, smoking history, and lung cysts) and continuous parameters (number of cysts, lung cyst volume, and largest cyst diameter and volume). Logistic regression analyses were used to identify the risk factors associated with pneumothorax. MEASUREMENTS AND MAIN RESULTS: Twenty-four percent (48/198) of patients with BHDS had a history of pneumothorax. The presence of lung cysts was significantly associated with pneumothorax (p = 0.006). Total lung cyst volume, largest cyst diameter and volume, and every parameter related to the number of lung cysts were significantly associated (p < 0.0001) with pneumothorax. A logistic regression analysis showed that only the total number of cysts in the right parenchymal lower lobe and the total number of cysts located on the pleural surface in the right middle lobe were needed to classify a patient as to whether or not he or she was likely to have a pneumothorax. Exon location of the BHD mutation was associated with the numbers of cysts (p = 0.0002). CONCLUSIONS: This study indicates that patients with BHDS have a significant association between lung cysts and spontaneous pneumothorax.

Evaluation and management of renal tumors in the Birt-Hogg-Dubé syndrome.

PURPOSE: Herein we describe the evaluation and management of renal tumors in Birt-Hogg-Dubé (BHD), an autosomal dominant disorder predisposing to cutaneous fibrofolliculomas, pulmonary cysts, spontaneous pneumothorax and renal tumors. MATERIALS AND METHODS: A total of 124 affected individuals underwent comprehensive clinical evaluation, including body computerized tomography, to determine cutaneous, pulmonary and renal manifestations of BHD. Of these individuals 14 had their renal tumors managed at our institution. RESULTS: Of the 124 BHD affected individuals 34 (27%) had renal tumors of various histologies, most commonly hybrid oncocytic tumor and chromophobe renal carcinoma. Average age at renal tumor detection was 50.4 years and multiple tumors were found in a majority of patients. Some patients with renal tumors were identified that did not have the characteristic cutaneous hallmarks of BHD. In 4 of the 14 patients treated at our institution small (less than 3 cm) renal tumors were observed, while 10 others underwent a total of 12 renal procedures, including 4 radical and 8 partial nephrectomies. At a median of 38 months of followup 5 of these 10 patients remained free of disease, 3 had small renal tumors and 2 died of metastatic renal cancer. CONCLUSIONS: Patients with BHD are at risk for multiple renal tumors that are often malignant and can metastasize. Individuals at risk or affected by BHD should be radiographically screened for renal tumors at periodic intervals and they are best treated with nephron sparing surgical approaches. Genetic testing for this syndrome is now available.

Germline BHD-mutation spectrum and phenotype analysis of a large cohort of families with Birt-Hogg-Dubé syndrome.

Birt-Hogg-Dubé syndrome (BHD), a genodermatosis characterized by multiple hamartomas of the hair follicle (fibrofolliculoma), predisposes individuals to an increased risk of developing renal neoplasms and spontaneous pneumothorax. Previously, we localized the BHD locus (also known as FLCN) to chromosome 17p11.2 by linkage analysis and subsequently identified germline mutations in a novel gene in probands from eight of the nine families with BHD in our screening panel. Affected members of five of the families inherited an insertion/deletion of a cytosine in a C8 tract in exon 11. This mutation was also identified by exon 11 screening in probands from 22 of 52 additional families with BHD and therefore represents a hypermutable "hotspot" for mutation in BHD. Here, we screened the remaining 30 families from this large BHD cohort by direct sequence analysis and identified germline BHD mutations in 84% (51/61) of all families with BHD recruited to our study. Mutations were located along the entire length of the coding region, including 16 insertion/deletion, 3 nonsense, and 3 splice-site mutations. The majority of BHD mutations were predicted to truncate the BHD protein, folliculin. Among patients with a mutation in the exon 11 hotspot, significantly fewer renal tumors were observed in patients with the C-deletion than those with the C-insertion mutation. Coding-sequence mutations were not found, however, in probands from two large families with BHD whose affected members shared their family's BHD-affected haplotype. Of the 53 families with BHD whose members inherited either a germline mutation or the affected haplotype, 24 (45%) had at least one member with renal neoplasms. Three families classified with familial renal oncocytoma were identified with BHD mutations, which represents the first disease gene associated with this rare form of renal neoplasm. This study expands the BHD-mutation spectrum and evaluates genotype-phenotype correlations among families with BHD.