The clinical characteristics of East Asian patients with Birt-Hogg-Dubé syndrome

Familial pulmonary cysts: A clue to diagnose Birt-Hogg-Dubé syndrome: A case report and literature review

Birt-Hogg-Dubé syndrome (BHD) is an inherited autosomal dominant condition caused by germline mutations in the FLCN gene, mapped to chromosome 17p11.2. Typical manifestations include pulmonary cysts, spontaneous pneumothorax, fibrofolliculomas, and kidney neoplasms. This report details the case of a 56-year-old female non-smoker diagnosed with multiple pulmonary cysts, presenting with a history of recurrent spontaneous pneumothorax. A computed tomography (CT) scan of her daughter revealed similar pulmonary cysts, raising suspicion of BHD. Further abdominal enhanced CT revealed a left renal tumour and cutaneous fibrofolliculomas on her daughter's neck. Consequently, whole-exome sequencing confirmed an FLCN germline mutation in the patient and three relatives, establishing a diagnosis of BHD. This case highlights the importance of familial pulmonary cysts as a clue for diagnosing BHD, providing crucial insights into comparable clinical presentations.

Outstanding Characteristics of Birt-Hogg-Dube Syndrome in Korea

Birt-Hogg-Dube (BHD) is a rare genetic disorder characterized by multiple lung cysts, typical skin manifestations, and renal tumors. We prospectively enrolled thirty-one subjects from four South Korean institutions with typical lung cysts, and next-generation sequencing was conducted. We prospectively enrolled thirty-one subjects from four Korean institutions with typical lung cysts. Next-generation sequencing was performed to investigate mutations in the following genes: FLCN, TSC1, TSC2, CFTR, EFEMP2, ELN, FBLN5, LTBP4, and SERPINA1. BHD was diagnosed in 11 of the 31 enrolled subjects (35.5%; FLCN mutations). Notably, we identified three novel mutations (c.1098G>A, c.139G>T, and c.1335del) that have not been previously reported. In addition to FLCN mutations, we also observed mutations in CFTR (16.1%), LTBP4 (9.7%), TSC2 (9.7%), TSC1 (3.2%), ELN (3.2%), and SERPINA1 (3.2%). According to a systematic review of 45 South Korean patients with BHD, the prevalence of pneumothorax (72.7%) was greater in South Korea than in the rest of the world (50.9%; p = 0.003). The prevalence of skin manifestations (13.6%) and renal tumors (9.1%) was lower in Korea than in the rest of the world, at 47.9% [p < 0.001] and 22.5% [p = 0.027], respectively). This study confirmed a significant prediction model for BHD based on age, number of lung cysts (>40), and maximal diameter of lung cysts (>2 cm) regardless of skin manifestations and renal tumors. Importantly, three novel mutations (c.1098G>A, c.139G>T, and c.1335del) were identified. In conclusion, South Korean patients with BHD display characteristics that are different from those observed in patients of other nationalities. Detailed characterization of lung cysts is needed to define BHD, especially in South Korea, even if patients do not present with skin or renal lesions.

PRDM10 directs FLCN expression in a novel disorder overlapping with Birt-Hogg-Dubé syndrome and familial lipomatosis

Birt-Hogg-Dubé syndrome (BHD) is an autosomal dominant disorder characterized by fibrofolliculomas, pulmonary cysts, pneumothoraces and renal cell carcinomas. Here, we reveal a novel hereditary disorder in a family with skin and mucosal lesions, extensive lipomatosis and renal cell carcinomas. The proband was initially diagnosed with BHD based on the presence of fibrofolliculomas, but no pathogenic germline variant was detected in FLCN, the gene associated with BHD. By whole exome sequencing we identified a heterozygous missense variant (p.(Cys677Tyr)) in a zinc-finger encoding domain of the PRDM10 gene which co-segregated with the phenotype in the family. We show that PRDM10Cys677Tyr loses affinity for a regulatory binding motif in the FLCN promoter, abrogating cellular FLCN mRNA and protein levels. Overexpressing inducible PRDM10Cys677Tyr in renal epithelial cells altered the transcription of multiple genes, showing overlap but also differences with the effects of knocking out FLCN. We propose that PRDM10 controls an extensive gene program and acts as a critical regulator of FLCN gene transcription in human cells. The germline variant PRDM10Cys677Tyr curtails cellular folliculin expression and underlies a distinguishable syndrome characterized by extensive lipomatosis, fibrofolliculomas and renal cell carcinomas.

Characteristic Chest Computed Tomography Findings for Birt-Hogg-Dube Syndrome Indicating Requirement for Genetic Evaluation

Background: Chest computed tomography (CT) findings are important for identifying Birt−Hogg−Dube (BHD) syndrome. However, the predictive power of classical criteria for chest CT findings is weak. Here, we aimed to identify more specific chest CT findings necessitating genetic examination for FLCN gene mutations. Methods: From June 2016 to December 2017, we prospectively enrolled 21 patients with multiple bilateral and basally located lung cysts on chest CT with no other apparent cause, including cases with and without spontaneous primary pneumothorax. All enrolled patients underwent FLCN mutation testing for diagnosis confirmation. Results: BHD was diagnosed in 10 of 21 enrolled patients (47.6%). There were no differences in clinical features between the BHD and non-BHD groups. Maximal cyst diameter was significantly greater in the BHD group (mean ± standard deviation; 4.1 ± 1.1 cm) than in the non-BHD group (1.6 ± 0.9 cm; p < 0.001). Diversity in cyst size was observed in 100.0% of BHD cases and 18.2% of non-BHD cases (p = 0.001). Morphological diversity was observed in 100.0% of BHD cases and 54.6% of non-BHD cases (p = 0.054). Areas under the receiver operating characteristic curves for predicting FLCN gene mutations were 0.955 and 0.909 for maximal cyst diameter and diversity in size, respectively. The optimal cut-off value for maximal diameter FLCN mutations prediction was 2.1 cm (sensitivity: 99%; specificity: 82%). Conclusions: Reliable chest CT features suggesting the need for FLCN gene mutations screening include variations in cyst size and the presence of cysts > 2.1 cm in diameter, predominantly occurring in the bilateral basal lungs.

Heterozygous germline FLCN mutation in Birt-Hogg-Dubé syndrome with bilateral renal hybrid oncocytic/chromophobe tumor and unilateral renal chromophobe cell carcinoma: a case report

BACKGROUND

Birt-Hogg-Dubé (BHD) syndrome is a rare autosomal dominant tumor syndrome caused by Folliculin (FLCN) gene mutation. The clinical manifestations are diverse, and the renal tumor is the most serious.

CASE PRESENTATION

We report the case of a 51-year-old female with multiple space-occupying lesions in both kidneys, as well as bilateral renal cysts and multiple lung cysts. The resected tumors were finally diagnosed as bilateral renal hybrid oncocytic/chromophobe tumor (HOCT) and unilateral chromophobe cell carcinoma. A history of pneumothorax surgery 4 years ago was convinced. All of these strongly suggested the possibility of BHD syndrome. Gene test confirmed a heterozygous germline FLCN nonsense mutation (c.1429C > T, p.Arg477Ter). The patient is still doing well after 20 months of follow-up (cut-off date July 2022).

CONCLUSION

This is a case of BHD syndrome presented with bilateral renal tumor, renal cysts, and multiple lung cysts, and confirmed by gene testing. Patients with any combination of one or more of the manifestations should remain alert to the BHD syndrome. Our report will help to deepen the understanding of the clinicopathological features and molecular changes of BHD syndrome.

Birt-Hogg-Dubé syndrome encountered at rare lung disease clinic in Anhui province, China

Background

Diagnosis of rare diseases remains a challenge in China. We describe our experience with Birt-Hogg-Dubé syndrome (BHDS) encountered at a Rare Lung Disease Clinic recently established in China.

Methods

After the first patient with BHDS was recognized in 2017, a Rare Lung Disease Clinic with a multidisciplinary team of specialists was established. We retrospectively analyzed the data of consecutive patients with BHDS encountered from inception to December 2021.

Results

There were 1, 1, 15, 12 and 21 cases with BHDS diagnosed from year 2017 to 2021, respectively. All 50 patients (34 women) were of Han race with a mean age of 47.4 years. The common manifestations were pulmonary cysts (98%), pneumothorax (54%) and skin lesions (68%). Renal cancer was detected in two patients and renal angiomyolipoma in four other patients. The main presentations leading to diagnosis were pneumothorax (42%), family screening (36%), and lung cysts identified on radiologic imaging (20%). The average delay in diagnosis was 8.3 years, and 4.7 years in patients with only pulmonary cysts. The most frequent pathogenic variant was c.1285del/dup on exon 11 (23%) among 44 patients confirmed by genetic testing. Renal cancer has not been found on follow-up surveillance thus far.

Conclusions

Increasing number of patients with BHDS are being recognized in China, facilitated by establishment of a Rare Lung Disease Clinic. Pulmonary cysts and pneumothorax were commonly encountered features, but skin lesions appeared to be more prevalent in Chinese subjects than previously reported in other Asian countries.

Clinical and Genetic Comparison of Birt–Hogg–Dubé Syndrome (Hornstein–Knickenberg Syndrome) in Chinese: A Systemic Review of Reported Cases

Background

Birt–Hogg–Dubé syndrome (BHD), also named Hornstein–Knickenberg syndrome, is a rare autosomal dominant disease characterized by lung cysts, recurrent pneumothoraxes, renal cell carcinoma and skin fibrofolliculomas.

Purpose

This study summarizes the clinical and genetic information of Chinese BHD patients from all available reported cases and explores the relationship between the clinical and genetic spectrum in the hope of improving the prognosis of Chinese BHD patients.

Methods

Relative studies were collected by searching PubMed, Cochrane Library, Embase, OVID medicine, SinoMed, Web of Science, China National Knowledge Infrastructure, Wanfang Data and China Hospital Knowledge Database from January 1, 1977 to December 31, 2021. The search strategy included the following term keys: (Birt–Hogg–Dubé syndrome OR Hornstein-Kinckenberg syndrome OR familial pulmonary cysts OR familial spontaneous pneumothorax OR fibrofolliculomas OR trichodiscomas OR inherited renal cancer syndromes OR FLCN) AND (Chinese OR China).

Results

In total, 287 Chinese patients from 143 families described in 31 references were included in this article. Chinese BHD patients tended to present more pulmonary symptoms but fewer skin lesions and renal malignancies, which appeared to be atypical when compared with Caucasian patients. The FLCN mutation spectrum among Chinese BHD patients was established with the mutational hot spot c.1285depC/delC as the most frequent mutation. In addition, this mutation spectrum also showed some differences from other races, with a relatively frequent large deletion c.872–429_1740+1763del (exon 9–14 deletion) reported only in Chinese individuals but no observation of the two mutational hot spots found in Japanese individuals. We also attempted to establish potential pheno-genotype correlations in Chinese BHD patients, but the results were negative.

Conclusion

To improve the prognosis of BHD patients, physicians need to increase their awareness of BHD by focusing on the family history of pneumothorax as well as skin lesions in patients with lung cysts and promptly advising patients on genetic sequencing.

Genetic insight into Birt-Hogg-Dubé syndrome in Indian patients reveals novel mutations at FLCN

Background

Birt-Hogg-Dubé syndrome (BHDS) is a rare monogenic condition mostly associated with germline mutations at FLCN. It is characterized by either one or more manifestations of primary spontaneous pneumothorax (PSP), skin fibrofolliculomas and renal carcinoma (chromophobe). Here, we comprehensively studied the mutational background of 31 clinically diagnosed BHDS patients and their 74 asymptomatic related members from 15 Indian families.

Results

Targeted amplicon next-generation sequencing (NGS) and Sanger sequencing of FLCN in patients and asymptomatic members revealed a total of 76 variants. Among these variants, six different types of pathogenic FLCN mutations were detected in 26 patients and some asymptomatic family members. Two of the variants were novel mutations: an 11-nucleotide deletion (c.1150_1160delGTCCAGTCAGC) and a splice acceptor mutation (c.1301-1G > A). Two variants were Clinvar reported pathogenic mutations: a stop-gain (c.634C > T) and a 4-nucleotide duplication (c.1329_1332dupAGCC). Two known variants were: hotspot deletion (c.1285delC) and a splice donor mutation (c.1300 + 1G > A). FLCN mutations could not be detected in patients and asymptomatic members from 5 families. All these mutations greatly affected the protein stability and FLCN-FNIP2 interaction as observed by molecular docking method. Family-based association study inferred pathogenic FLCN mutations are significantly associated with BHDS.

Conclusion

Six pathogenic FLCN mutations were detected in patients from 10 families out of 15 families in the cohort. Therefore, genetic screening is necessary to validate the clinical diagnosis. The pathogenic mutations at FLCN affects the protein–protein interaction, which plays key roles in various metabolic pathways. Since, pathogenic mutations could not be detected in exonic regions of FLCN in 5 families, whole genome sequencing is necessary to detect all mutations at FLCN and/or any undescribed gene/s that may also be implicated in BHDS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02326-5.

Case Report: A BRCA2 Mutation Identified Through Next-Generation Sequencing in a Birt–Hogg–Dubè Syndrome Family

Birt–Hogg–Dubé syndrome (BHDS) is a rare autosomal dominant inherited disorder caused by a mutation in folliculin (FLCN) gene transmitted via germline autosomal dominant pattern. Patients with this syndrome have an increased susceptibility to renal cell carcinoma, lung cysts, spontaneous pneumothorax, and benign skin hamartomas, and its diagnosis is not easy and consequently underestimated. Several mutations have been identified in FLCN gene, among which the majority of alterations are frameshift (insertion/deletion), nonsense, or splice-site mutations that generally produce unfunctional truncated FLCN proteins. Our aim is to present a case of a BHDS family whose proband is a 56-year-old patient who has been experiencing multiple disorders, has an FLCN genetic mutation, and has also been identified to have a pathogenic variant in BRCA2 gene. Our further purpose is to emphasize the importance of the next-generation sequencing (NGS) approach to identify potential multiple germline mutations in complex and rare oncologic disorders, allowing strict and more targeted cancer screening programs.

Birt-Hogg-Dubé syndrome in Chinese patients: a literature review of 120 families

Objective

To clarify the epidemiological and clinical features of Birt–Hogg–Dubé syndrome (BHDS) in Chinese patients.

Methods

We identified reports on Chinese patients with BHDS by searching the China Academic Journals Database, Wanfang Chinese Database, and PubMed databases, either in Chinese or English languages published from January 1, 2008 to December 31, 2020. Studies without sufficient clinical data were excluded and cases under 18 years old were excluded.

Results

Twenty papers were included and comprised 120 families with 221 cases. Most families with BHDS were reported from institutions in Beijing (66.7%) and Jiangsu Province (15.8%); 80.8% of cases were reported within the past five years. The average duration from clinical presentation to diagnosis was 9.6 years. The average age was 47.0 ± 13.9 years (range, 18–84 years) and the ratio of male to female was 1:1.6. The most common manifestations of BHDS were multiple pulmonary cysts (92.4%), spontaneous pneumothorax (71.0%), skin lesions (18.1%) and renal tumors (3.6%). Pulmonary cysts were predominantly distributed in the lower lobe on chest CT imaging. Family history of spontaneous pneumothorax was identified in 84.7% of the families and average number of pneumothoraxes was 1.8 (range, 1–6). The FLCN gene mutation c.1285dupC/delC in exon 11 was the most frequent mutation observed (17.4% of patients). The recurrence rate of pneumothorax after conservative treatment (including tube thoracostomy) was 29/41 (71%) while the pneumothorax recurred after surgical treatment (pulmonary bullectomy or pleurodesis) in only 4/37 (11%).

Conclusions

Although BHDS has been increasingly reported in the recent years, only minority of families were reported from institutions outside of Beijing and Jiangsu Province. The dominant clinical manifestations were pulmonary cysts associated with recurrent pneumothorax, while skin lesions and renal tumors were less commonly reported. Delayed diagnosis along with suboptimal management appear to represent critical challenges for Chinese patients with BHDS.