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

Birt-Hogg-Dubé syndrome in an overall view: Focus on the clinicopathological prospects in renal tumors

Birt-Hogg-Dubé syndrome (BHD) represents a rare autosomal dominant tumor predisposition syndrome characterized by skin lesions, lung cysts, and renal tumors. The predominant histological subtypes of BHD-related renal tumors include hybrid oncocytoma-chromophobe tumors, oncocytomas, and chromophobe renal cell carcinomas, all exhibiting eosinophilic/oncocytic features. Immunohistochemistry staining for KIT (CD117) and CK7 exhibits variability in these tumor types. Germline mutations in FLCN have been consistently identified. Generally, patients with BHD demonstrate a favorable prognosis with minimal metastatic potential. Nonetheless, the comprehensive elucidation of pathological characteristics of BHD remains incomplete, particularly in BHD-associated renal tumors that deviate from the previously identified subtypes, thereby complicating the differential diagnosis. In this review, we provide a comprehensive overview of BHD encompassing epidemiology, clinical manifestations, genetic and molecular pathogenesis, as well as clinical diagnostic modalities. Emphasis is placed on clinicopathological features, specifically focusing on BHD-associated renal tumors. Collectively, this review aims to present the latest insights into BHD which benefits in the early detection, therapeutic decision-making, and prognosis prediction in BHD cases, and deepen the understanding of sporadic renal tumors.

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.

Coexistent Sjogren's syndrome and Birt-Hogg-Dube´ syndrome: a case report

We report a rare case of Sjogren's syndrome complicated with Birt-Hogg-Dubé syndrome (BHDS) not previously mentioned in the literature. Further, there is insufficient evidence linking the two diseases. Here, we review existing diagnostic algorithms for diagnosing diffuse cystic lung disease and provide new insights. The patient initially complained of thirst and dry eyes for ten years, and gradually developed shortness of breath. After admission, physical examination showed five missing teeth, decreased respiratory sounds in both lower lungs, and Velcro rales. Computed tomography showed multiple thin-walled cystic lesions in both lungs. Initial xerophthalmia and labial gland biopsy seemed to reveal a pulmonary cystic change associated with Sjogren's syndrome. Before discharge, a rash suspected to indicate a fibrofollicular tumor in the neck was observed, and then FLCN variant has been found. The challenges how to clarify the diagnosis of DCLD causes are discussed.

Renal Cell Tumor and Cystic Lung Disease: A Genetic Link for Generalists to Be Aware of

Birt-Hogg-Dubé syndrome (BHDS) is a rare autosomal dominant condition characterized by multiple pulmonary cysts, fibrofolliculomas, and renal cell carcinoma. The typical presentations leading to diagnosis include fibrofolliculomas and spontaneous pneumothoraxes. We present a case of a 52-year-old Chinese male who was diagnosed with BHDS after the incidental pickup of an echogenic heterogenous lesion on an abdominal ultrasound done to investigate an abnormal liver function test. The presence of renal cell carcinoma with cystic pulmonary disease should prompt the clinician to consider the diagnosis of BHDS. Knowledge of extrapulmonary findings of common cystic lung diseases may contribute to improved diagnosis of this condition.

Clinical and genetic features of 334 Asian patients with Birt-Hogg-Dubé syndrome (BHDS) who presented with pulmonary cysts with or without a history of pneumothorax, with special reference to BHDS-associated pneumothorax

BACKGROUND

The clinical pulmonary manifestations and genetic features of Birt-Hogg-Dubé syndrome (BHDS) in Asian patients remained unclear. We aimed to clarify the clinical features of BHDS-associated pneumothorax (PTX) and retrospectively investigate potential contributing factors in the largest Asian cohort to date.

METHODS

We reviewed the clinical and genetic data collected in 2006-2017, from the BHDS patients who were Asian and presented with pulmonary cysts with or without a history of PTX.

RESULTS

Data from 334 (41.3% males; 58.7% females) patients from 297 unrelated families were reviewed. Among them, 314 (94.0%) patients developed PTX. The median age at the first occurrence of PTX was 32 years, which was significantly lower in males (P = 0.003) and patients without notable skin manifestations (P < 0.001). Seventy-six (24.2%) patients experienced their first PTX episode before the age of 25 years. PTX simultaneously occurred in the bilateral lungs of 37 (11.8%) patients. Among 149 patients who had their first PTX episode at least 10 years before BHDS diagnosis, PTX occurred more frequently in males (P = 0.030) and light smokers than in nonsmokers (P = 0.014). The occurrence of PTX peaked in the early 30s and gradually decreased with age but remained high in females (P = 0.001). We identified 70 unique FLCN germline variants, including duplications (46.4%), substitutions (7.1%), insertions/deletions (30.0%), and variants affecting splicing (12.5%). Approximately 80% of Asian patients suspected of having BHDS could be genetically diagnosed by examining FLCN exons 7, 9, 11, 12, and 13. No apparent genotype-phenotype correlation regarding pulmonary manifestations was identified.

CONCLUSIONS

Our findings indicate that sex, smoking history, and skin manifestations at BHDS diagnosis significantly influence the clinical features of BHDS-associated PTX. These findings may contribute to the appropriate management and treatment of BHDS-associated PTX.

Exons 1-3 deletion in FLCN is associated with increased risk of pneumothorax in Chinese patients with Birt-Hogg-Dubé syndrome

BACKGROUND

The pathogenic variants responsible for Birt-Hogg-Dubé syndrome (BHDS) in folliculin (FLCN) gene mostly consist of point mutations. Although large intragenic deletions/duplications have been reported in several case reports, the relationship between large intragenic deletions/duplications and phenotype in BHDS remains unclear.

METHODS

We retrospectively identified and reviewed patients with a large intragenic deletion spanning exons 1-3 and analyzed their phenotypic features to compare with those of point mutation carriers in our hospital from January 1, 2017 to August 31, 2022.

RESULTS

Twenty unique point mutations (including 4 novel mutations) were detected in 62 patients from 45 families (90%). Exons 1-3 deletion were identified in 8 patients from 5 families (10%) that resided in the same region, Feidong County of Anhui Province, China. Breakpoint analysis indicated that all the deletion breakpoints were flanked by Alu repeats. The prevalence of exons 1-3 deletion carriers in Feidong County was 8.1-times higher than that for BHDS in Anhui Province, suggesting a clustered phenomenon of exons 1-3 deletion. Significantly increased risk of pneumothorax was observed in those with exons 1-3 deletion compared with point mutations (91% vs. 58%, p value 0.047). The risk of renal cancer may be higher in those with exons 1-3 deletion than for those with point mutations (18% vs. 4%, p > 0.05).

CONCLUSIONS

Large intragenic deletion of exons 1-3 in FLCN was identified as a local aggregation phenomenon in Feidong County, China, and was associated with a significantly higher risk of pneumothorax compared to those with point mutations.

Birt-Hogg-Dubé syndrome with c.1579_1580insA variant in a Chinese family: a case report

Birt-Hogg-Dubé (BHD) syndrome, is a rare genetic disease with heterogeneous manifestations in different populations. In this study, we reported a Chinese female BHD case and her family members with c.1579_1580insA variant in FLCN gene, who were characterized by diffused pulmonary cysts/bulla, and reviewed another five familial BHD cases in China. Based on these cases, recurrent spontaneous pneumothorax is likely to be the first symptom for BHD in Chinese patients, with particularly but not limited to c.1579_1580insA variant. Therefore, attention to the early diagnosis of BHD in China should focus on pulmonary signs, but skin or kidney lesions still can not be neglected.

Birt-Hogg-Dubé syndrome: Another mTOR phenomenon

Birt-Hogg-Dubé syndrome is an uncommon autosomal dominant systemic disorder with cutaneous findings notable for fibrofolliculomas or trichodiscomas on the scalp, face, neck, and trunk. These cutaneous signs are associated with bilateral renal cell carcinoma, benign renal cysts, pulmonary cysts, and spontaneous pneumothorax. Given its autosomal dominant inheritance pattern, the successful diagnosis of Birt-Hogg-Dubé syndrome (BHDS) may elucidate a diagnosis in family members. BHDS results from a mutation in the FLCN gene encoding the folliculin protein, a transcriptional regulator of the mammalian target of rapamycin signaling pathway. Like tuberous sclerosis, BHDS's clinical features may subside with the use of oral rapamycin for mammalian target of rapamycin inhibition, a theoretical concept meriting exploration. Although its prevalence in the general population has been estimated at 2 cases per million, BHDS has been detected in a few patients from the nearby Portuguese-lineage quarter of the city of Newark, a disproportionate prevalence possibly explained by the founder effect.

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.