Clinical and genetic study of a large Chinese family presented with familial spontaneous pneumothorax

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.

Clinical Characteristics and Genetic Analysis of a Family With Birt-Hogg-Dubé Syndrome and Congenital Contractural Arachnodactyly

Background: Birt-Hogg-Dubé (BHD) syndrome and congenital contractural arachnodactyly (CCA) or Beals-Hecht syndrome are clinically rare autosomal dominant genetic diseases. In this study, we describe an extremely rare family with BHD syndrome and CCA.

Objective: To investigate the clinical and genetic characteristics of a family with BHD syndrome and CCA.

Methods: We describe the clinical characteristics, family history, and clinical manifestations of the patient’s family members. The patient underwent a blood test, computed tomography (CT) of the chest, color Doppler ultrasound of the abdomen and heart, and digital radiography of the hands. Whole exome sequencing was performed on his family members.

Results: Two years ago, the male proband developed chest tightness and shortness of breath that was accompanied by an irritating cough as well as repeated (four times) spontaneous pneumothorax. The chest CT indicated spontaneous pneumothorax on the right side and cyst and bullae in both lungs. He had no kidney tumors or skin lesions. His son had a history of pulmonary bullae and experienced spontaneous pneumothorax twice. The proband, his mother, and his son were all born with a hand deformity. The sequencing results demonstrated that both the proband and his son had heterozygous variations of the folliculin (FLCN) gene c.1015C > T (p. Gln339Ter) and fibrillin-2 (FBN2) gene c.3485G > A (p. Cys1162Tyr), which are associated with BHD syndrome and CCA, respectively.

Conclusion: For patients with chest tightness, shortness of breath, recurrent spontaneous pneumothorax, and congenital hand deformity without inducement, genetic testing should be carried out as soon as possible to make a clear diagnosis, which can then guide treatment and genetic counseling.

A systematic review assessing the existence of pneumothorax-only variants of FLCN. Implications for lifelong surveillance of renal tumours

Individuals with Birt-Hogg-Dubé syndrome (BHDS) may develop fibrofolliculomas, pneumothorax and/or renal cell carcinoma (RCC). Currently, all patients with pathogenic FLCN variants are recommended to have renal surveillance. It has however been suggested that some FLCN variants only cause pneumothorax, which would make surveillance unnecessary in certain cases. This review assesses this possibility. We provide an up-to-date analysis of clinical and genetic features of BHDS. The PUBMED database was systematically searched to find all articles describing patients with pathogenic FLCN variants. The relevant clinical and genetic features of these patients were recorded and analysed. The prevalence of pneumothorax, pulmonary cysts, RCC and characteristic skin lesions in BHDS were 50.9% (n = 1038), 91.9% (n = 720), 22.5% (n = 929) and 47.9% (n = 989), respectively. There was a higher prevalence of pneumothoraces (p < 0.0001) but lower prevalence of dermatological findings (p < 0.0001) in patients from East Asia compared to North America or Europe. Of the 194 pathogenic FLCN variants, 76 could be defined as 'pneumothorax-only'. Pneumothorax only pathogenic variants (POPVs) were distributed throughout the gene, and there were no statistical differences in variant type. The majority of POPVs (65/76) affected no more than three individuals. Individuals with 'POPVs' also tended to be younger (45 vs. 47 years, p < 0.05). Many apparent POPVs in the literature could result from variable expressivity, age-related penetrance and other confounding factors. We therefore recommend that all individuals found to carry a pathogenic FLCN variant be enroled in lifelong surveillance for RCC.

Identification of a Novel Pathogenic Folliculin Variant in a Chinese Family With Birt-Hogg-Dubé Syndrome (Hornstein-Knickenberg Syndrome)

Birt–Hogg–Dubé syndrome (BHDS), which is also called Hornstein-Knickenberg syndrome (HKS), is a hereditary autosomal dominant disorder caused by germline mutations in the folliculin gene (FLCN, NM_144997). More pulmonary manifestations (pulmonary cysts and recurrent pneumothoraxes) but fewer skin fibrofolliculomas and renal malignancy are found in Asian BHDS patients compared with other BHDS patients. The atypical manifestation can easily lead to a missed or delayed diagnosis. Here, we report a Chinese family with BHDS that presented with primary spontaneous pneumothorax (PSP) and extensive pulmonary cysts in the absence of skin lesions or renal neoplasms. Next-generation sequencing (NGS) was used to sequence the FLCN gene, and Sanger sequencing was carried out on the samples to confirm the presence of these variants. Among the 13 family members, a novel frameshift variant of FLCN (c.912delT/p.E305KfsX18) was identified in seven individuals. This variant has not been reported before. Bioinformatics analysis showed that the novel variant might lead to a premature stop codon after 18 amino acid residues in exon 9, and this may affect the expression level of FLCN. The identification of this novel frameshift variant of FLCN not only further confirms the familial inheritance of BHDS in the proband but also expands the mutational spectrum of the FLCN gene in patients with BHDS.

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

Background

Birt-Hogg-Dube (BHD) syndrome is an autosomal dominant disease that has been characterized by skin lesions, multiple pulmonary cysts, spontaneous pneumothorax, and renal tumors, but the patients in Asian countries may show fewer symptoms. We aimed to explore and summarize the clinical features of BHD patients in East Asia to facilitate early diagnosis and timely interventions.

Methods

We collected and analyzed the clinical data of patients diagnosed with BHD in our hospital by reviewing medical records. We performed a systematic literature search regarding the presenting clinical features in BHD patients from China, Japan, and Korea and then reviewed the publications that were identified.

Results

In our hospital, 10 patients were diagnosed with BHD from April 2015 to September 2019. After reviewing the literature, we recruited 38 articles, including 12, 20, and 6 reports from China, Japan, and Korea, respectively. A total of 166 patients were included in this study, and 100 of them (60.2%) were females. Multiple pulmonary cysts were present in 145 patients (87.3%), and 124 patients (74.7%) had a history of pneumothorax on at least one occasion. Skin biopsy confirmed fibrofolliculomas (FFs) alone in 22 patients (13.3%), trichodiscomas (TDs) alone in 3 patients (1.8%), and both FFs and TDs in 7 patients (4.2%). Renal carcinoma only occurred in 12 (7.2%) patients. The most frequent genetic mutations in East Asian patients were c.1285delC on exon 11 (18.4%), c.1285dupC on exon 11 (18.4%), and c.1347_1353dupCCACCCT on exon 12 (8.2%).

Conclusions

Our findings suggested that pulmonary cysts are the most frequent radiological findings, and pneumothorax is the most common symptom in East Asian patients with BHD, and that skin lesions and kidney involvement are less frequent. To make an early diagnosis and minimize the severity of complications, careful observation, and timely genetic examination of the FLCN gene is essential.

Recurrent primary spontaneous pneumothorax in a large Chinese family: a clinical and genetic investigation

BACKGROUND

Primary spontaneous pneumothorax (PSP) is a common manifestation of Birt-Hogg-Dubé (BHD) syndrome, which is an autosomal dominant disorder caused by mutation of the folliculin (FLCN) gene. This study was established to investigate the mutation of the FLCN gene and the phenotype in a family with PSP.

METHODS

We investigated the clinical and genetic characteristics of a large Chinese family with recurrent spontaneous pneumothorax. Genetic testing was performed by Sanger sequencing of the coding exons (4-14 exons) of the FLCN gene.

RESULTS

Among ten affected members in a multi-generational PSP kindred, with a total of 18 episodes of spontaneous pneumothorax, the median age for the initial onset of pneumothorax was 42.5 years (interquartile range: 28.8-57.2 years). Chest computed tomography scan of the proband showed pulmonary cysts and pneumothorax. A novel nonsense mutation (c.1273C>T) in exon 11 of FLCN gene that leads to a pre-mature stop codon (p.Gln425*) was identified in the family. The genetic analysis confirmed the diagnosis of BHD syndrome in this family in the absence of skin lesions or renal tumors.

CONCLUSIONS

A novel nonsense mutation of FLCN gene was found in a large family with PSP in China. Our results expand the mutational spectrum of FLCN gene in patients with BHD syndrome.

FLCN-regulated miRNAs suppressed reparative response in cells and pulmonary lesions of Birt-Hogg-Dubé syndrome

Background

Birt-Hogg-Dubé Syndrome (BHDS) characterised by skin fibrofolliculomas, kidney tumour and pulmonary cysts/pneumothorax is caused by folliculin (FLCN) germline mutations. The pathology of both neoplasia and focused tissue loss of BHDS strongly features tissue-specific behaviour of the gene. Isolated cysts/pneumothorax is the most frequent atypical presentation of BHDS and often misdiagnosed as primary spontaneous pneumothorax (PSP). Deferential diagnosis of BHDS with isolated pulmonary presentation (PSP-BHD) from PSP is essential in lifelong surveillance for developing renal cell carcinoma.

Methods

The expression profiles of microRNAs (miRNAs) in cystic lesions of PSP-BHD and PSP were determined via microarray. The selected upregulated miRNAs were further confirmed in the plasma of an expanded cohort of PSP-BHD patients by reverse transcription quantitative PCR (RT-qPCR). Their diagnostic accuracy was evaluated. Moreover, the cellular functions and targeted signalling pathways of FLCN-regulated miRNAs were assessed in various cell lines and in the lesion tissue contexts.

Results

Cystic lesions of PSP-BHD and PSP showed different miRNAs profiles with a significant upregulation of miR-424–5p and let-7d-5p in PSP-BHD. The combination of the two effectively predicted BHDS patients. In vitro studies revealed a suppressive effect of FLCN on miR-424–5p and let-7d-5p expressions specifically in lung epithelial cells. The ectopic miRNAs triggered epithelial apoptosis and epithelial transition of mesenchymal cells and suppressed the reparative responses in cells and tissues with FLCN deficiency.

Conclusion

The upregulation of miR-424–5p and let-7d-5p by FLCN deficiency occurred in epithelial cells and marked the PSP-BHD condition, which contributed to a focused degenerative pathology in the lung of PSP-BHD patients.

A novel FLCN mutation in family members diagnosed with primary spontaneous pneumothorax

Background

Primary spontaneous pneumothorax (PSP) is a disease characterized by the accumulation of air in the pleural space between the lung and thoracic wall. It is more common in young, tall, thin, and asthenic men. A family history was reported for approximately 11.5% of individuals admitted with PSP. The literature has reported cases diagnosed with familial PSP, who have no manifestations of Birt–Hogg–Dubé (BHD) syndrome but mutations in different exons of the Folliculin (FLCN) gene. The aim of this study is to present a Turkish family in which 13 members from three generations of the same family developed recurrent isolated spontaneous pneumothorax with a novel mutation in the FLCN.

Methods

A male proband was diagnosed with spontaneous pneumothorax in the emergency department of the University of Health Sciences Haydarpasa Numune Training and Research Center, Istanbul, Turkey. His 12 relatives from three generations diagnosed with PSP, as revealed by his family history, were invited to the hospital to give blood samples for mutation analysis. The Sanger sequence data of FLCN were analyzed on the ENSEMBL website using SeqScape 3 and Codon Aligner software.

Results

A novel heterozygous mutation c. 1273C>T (p.Gln425Ter) was detected in exon 11 of the FLCN, which caused PSP in the proband and his 12 relatives tested using Sanger sequencing.

Conclusion

We found that a heterozygous mutation in exon 11 of FLCN c. 1273C>T (p.Gln425Ter), which was identified for the first time in our study, might cause isolated familial spontaneous pneumothorax.