Familial pneumothorax: towards precision medicine

ERN GENTURIS clinical practice guidelines for the diagnosis, surveillance and management of people with Birt-Hogg-Dubé syndrome

Birt-Hogg-Dubé syndrome (BHD syndrome) is an autosomal dominant multisystem disorder with variable expression due to pathogenic constitutional variants in the FLCN gene. Patients with BHD syndrome are predisposed to benign cutaneous fibrofolliculomas/trichodischomas, pulmonary cysts with an associated risk of spontaneous pneumothorax, and renal cell carcinoma. A requirement for updated International consensus recommendations for the diagnosis and management of BHD syndrome was identified. Based on a comprehensive literature review and expert consensus within the fields of respiratory medicine, urology, radiology, dermatology, clinical oncology and clinical genetics, updated recommendations for diagnosis, surveillance and management in BHD syndrome were developed. With the widespread availability of FLCN genetic testing, clinical scenarios in which a diagnosis should be considered and criteria for genetic testing were defined. Following a clinical and/or molecular diagnosis of BHD syndrome, a multidisciplinary approach to disease management is required. Regular renal cancer surveillance is recommended in adulthood and life-long, but the evidence base for additional tumour surveillance is limited and further research warranted. Recommendations for the treatment of cutaneous, pulmonary and renal manifestations are provided. Awareness of BHD syndrome needs to be raised and better knowledge of the clinical settings in which the diagnosis should be considered should enable earlier diagnosis. Further details, including areas for future research topics are available at: https://www.genturis.eu/l=eng/Guidelines-and-pathways/Clinical-practice-guidelines.html .

National survey on management of spontaneous pneumothorax from emergency department to specialised treatment: room for improvement

Introduction

Spontaneous pneumothorax (SP) affects both young, otherwise healthy individuals and older persons with known underlying pulmonary disease. Initial management possibilities are evolving and range from observation to chest tube insertion. SP guidelines suggest an individualized approach based on multiple factors such as symptoms, size of pneumothorax, comorbidity and patient preference.

Aim

With this Danish national survey we aimed to map organization of care including involved specialties, treatment choice, training, and follow-up plans to identify aspects, and optimization of spontaneous pneumothorax management.

Method

A survey developed by the national interest group for pleural medicine was sent to all departments of emergency medicine, thoracic surgery, respiratory medicine, and to relevant departments of abdominal or orthopaedic surgery.

Results

The response rate was 75 % (47 of 65). Overall, 21% of responding departments had no guideline for SP management, which was provided by multiple specialties with marked heterogeneity in choice of treatment including tube size, management during admission, and referral procedure to follow-up. Few departments required procedure training, and nearly all of the responders called for improvements in management of pneumothorax.

Conclusion

This survey suggests that SP management and care is delivered heterogeneously across Danish hospitals with marked difference between respiratory physicians, emergency physicians, general surgeons and thoracic surgeons. It is therefore likely that management is sub-optimal. There is a need for a common Danish SP guideline to ensure optimal treatment across involved specialties.

Expert Review on Spontaneous Pneumothorax: Advances, Controversies, and New Directions

For decades, there has been scanty evidence, most of which is of poor quality, to guide clinicians in the assessment and management of pneumothorax. A recent surge in pneumothorax research has begun to address controversies surrounding the topic and change the face of pneumothorax management. In this article, we review controversies concerning the etiology, pathogenesis, and classification of pneumothorax, and discuss recent advances in its management, including conservative and ambulatory management. We review the evidence base for the challenges of managing pneumothorax, including persistent air leak, and suggest new directions for future research that can help provide patient-centered, evidence-based management for this challenging cohort of patients.

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.

Aetiology of Primary Spontaneous Pneumothorax

Air in the pleural cavity is termed pneumothorax. When this occurs in the absence of trauma or medical intervention, it is called spontaneous pneumothorax. Primary spontaneous pneumothorax typically occurs in young patients without known lung disease. However, the idea that these patients have “normal” lungs is outdated. This article will review evidence of inflammation and respiratory bronchiolitis on surgical specimens, discuss the identification of emphysema-like change (i.e., blebs and bullae), the concept of pleural porosity and review recent data on the overexpression of matrix metalloproteinases in the lungs of patients who have had pneumothorax.

Utility of thoracic computed tomography to predict need for early surgery and recurrence after first episode of primary spontaneous pneumothorax

INTRODUCTION

CT imaging is not advocated by British Thoracic Society guidelines after first episode of primary spontaneous pneumothorax (PSP). There is emerging evidence that emphysema-like changes and CT-based dystrophy severity score (DSS) can predict need for early surgery and recurrence.

OBJECTIVES

We aimed to assess the role of DSS during first episodes of PSP in predicting the need for early surgery and recurrence.

METHODS

We conducted a retrospective analysis of consecutive PSP episodes (n=197) admitted to our institution from 1 January 2012 to 31 December 2017. DSS was calculated based on type, number and distribution of blebs and bullae. Patients were categorised as low-grade (0-3) or high-grade (4-6) DSS assessed by a thoracic radiologist.

RESULTS

Forty-five PSP patients had CT at first presentation. Eight patients had low-grade DSS; all were managed non-surgically and none had recurrence over 12 months. Thirty-seven patients had high-grade DSS. Of these, 25 (67.5%) were managed surgically, with three having contralateral recurrence over 12 months; 12 (32.5%) were managed non-surgically, and of these two patients had ipsilateral recurrence over 12 months.

CONCLUSION

DSS seems to predict the need for early surgery and recurrence and CT can be used to risk-stratify patients after a first episode of PSP.

Sudden unexpected death due to spontaneous pneumothorax caused by ruptured bilateral pulmonary bullae

Sudden unexpected death due to pneumothoraces caused by spontaneous rupture of bilateral pulmonary bullae is rare. This article reports the case of a 16-year-old girl who experienced this rare phenomenon without any precipitating factors. The patient did not have a history of chest pains or smoking but experienced chest tightness in the early morning and collapsed and died 4 h later. Autopsy identified the cause of death to be bilateral pneumothoraces and massive bilateral pulmonary collapse (atelectasis) due to ruptured apical bullae of the bilateral lungs. No injuries or other significant pathological findings were identified. A low body mass index (16.5) may have been a risk factor for the spontaneous tension pneumothoraces. In some situations, genetic counseling and testing may be helpful in identifying a heritable process associated with spontaneous pneumothoraces.

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.

Familial spontaneous pneumothorax: importance of screening for Birt-Hogg-Dubé syndrome

OBJECTIVES

The goal of this study was to investigate the prevalence of Birt-Hogg-Dubé (BHD) syndrome in patients with familial spontaneous pneumothorax (FSP) and the clinical characteristics of pneumothorax related to BHD syndrome compared with those of primary spontaneous pneumothorax.

METHODS

A total of 37 families diagnosed with FSP from 2007 to 2017 were enrolled in this study. The FLCN gene, which is responsible for BHD syndrome, was sequenced using the Sanger method in 25 probands. For the patients with confirmed BHD syndrome-related pneumothorax, clinical characteristics including the median onset age of pneumothorax, the male-to-female ratio, the mean height and body mass index (BMI) and the recurrence rate after different treatment modalities were obtained and compared with those of patients with primary spontaneous pneumothorax.

RESULTS

Of the 25 probands with FSP, 16 [64.0%, 95% confidence interval (CI) 43.8-84.2%] harboured FLCN germline mutations. In the patients with BHD syndrome-related pneumothorax, the median onset age of pneumothorax was 34 years; the male-to-female ratio was 1.3:1; and the mean height and BMI were 167.0 ± 8.6 cm and 23.6 ± 3.4 kg/m2, respectively. These characteristics were significantly different from those in patients with primary spontaneous pneumothorax from the same centre. The recurrence rate of BHD syndrome-related pneumothorax after conservative therapy was 53.1% (95% CI 38.6-67.5%) compared with 9.1% (95% CI 0-19.4%) after surgical treatment.

CONCLUSIONS

BHD syndrome is one of the most common causes of FSP. Patients with FSP should be recommended for mutation screening for the FLCN gene to facilitate early diagnosis and proper intervention.

Combining clinical, radiological and genetic approaches to pneumothorax management

Familial spontaneous pneumothorax (FSP) accounts for 10% of primary spontaneous pneumothoraces. Appropriate investigation of FSP enables early diagnosis of serious monogenic diseases and the practice of precision medicine. Here, we show that a pneumothorax genetics multidisciplinary team (MDT) can efficiently diagnose a range of syndromic causes of FSP. A sizeable group (73.6%) of clinically unclassifiable FSPs remains. Using whole genome sequencing we demonstrate that most of these cases are not known monogenic disorders. Therefore, clinico-radiological assessment by an MDT has high sensitivity for currently known clinically important monogenic causes of FSP, which has relevance for the design of efficient pneumothorax services.

An evidence-based review of primary spontaneous pneumothorax in the adolescent population

Primary spontaneous pneumothorax (PSP) is a relatively common problem in emergency medicine. The incidence of PSP peaks in adolescence and is most common in tall, thin males. Recent advances in the care of patients with PSP have called into question traditional approaches to management. This clinical review highlights the changing management strategies for PSP and concludes with a proposed evidence-based pathway to guide the care of adolescents with PSP.

Prevalence of Birt-Hogg-Dubé Syndrome Determined Through Epidemiological Data on Spontaneous Pneumothorax and Bayes Theorem

Background: Birt-Hogg-Dubé syndrome (BHD) is a rare inherited disorder characterized by cutaneous fibrofolliculomas, multiple pulmonary cysts, recurrent spontaneous pneumothorax (SP), and renal tumors. More than 40 years after its description, the prevalence of BHD in the general population remains unknown. This study aimed at determining the prevalence of BHD by applying the Bayes theorem of conditional probability to epidemiological data on SP. Methods: We performed a meta-analysis of published data on: (1) the probability of having BHD among patients with apparent primary SP (4 studies), (2) the incidence rate of primary SP in the general population (9 studies), and (3) the probability of experiencing a SP in BHD (16 studies). Results were corrected for SP relapses, stratified by gender and year of study publication (before and after 2000), and computed with the Bayes equation. Results: The probability of having BHD among patients with apparent primary SP was 0.09 (95% confidence interval: 0.07, 0.11) or 9%. It was 0.20 (0.14, 0.27) in women and 0.05 (0.04, 0.07) in men. The incidence rate of primary SP in the general population was 8.69 (6.58, 11.46) per 100,000 person-years (p-y). It was 3.44 (2.36, 4.99) per 100,000 p-y in women and 13.96 (10.72, 18.18) per 100,000 p-y in men, and was about 2 times higher in studies published after 2000 than in those published before 2000. The probability of experiencing at least one SP among patients with BHD was 0.43 (0.31, 0.54) or 43%, without gender difference. By combining these data in the Bayes equation, we found a prevalence of BHD in the general population of 1.86 (1.16, 3.00) per million, with values of 1.86 (1.02, 3.39) per million in men, and 1.88 (0.97, 3.63) per million in women. Conclusion: The prevalence of BHD in the general population is about 2 cases per million, without difference between genders.

Pleural effusions and pneumothorax: Beyond simple plumbing: Expert opinions on knowledge gaps and essential next steps

Pleural diseases affect millions of people worldwide. Pleural infection, malignant pleural diseases and pneumothorax are common clinical challenges. A large number of recent clinical trials have provided an evidence-based platform to evaluate conventional and novel methods to drain pleural effusions/air which reduce morbidity and unnecessary interventions. These successes have generated significant enthusiasm and raised the profile of pleural medicine as a new subspecialty. The ultimate goal of pleural research is to prevent/stop development of pleural effusions/pneumothorax. Current research studies mainly focus on the technical aspects of pleural drainage. Significant knowledge gaps exist in many aspects such as understanding of the pathobiology of the underlying pleural diseases, pharmacokinetics of pleural drug delivery, etc. Answers to these important questions are needed to move the field forward. This article collates opinions of leading experts in the field in highlighting major knowledge gaps in common pleural diseases to provoke thinking beyond pleural drainage. Recognizing the key barriers will help prioritize future research in the quest to ultimately cure (rather than just drain) these pleural conditions.

Recognizing genetic disease: A key aspect of pediatric pulmonary care

Advancement in technology has improved recognition of genetic etiologies of disease, which has impacted diagnosis and management of rare disease patients in the pediatric pulmonary clinic. This review provides an overview of genetic conditions that are likely to present with pulmonary features and require extensive care by the pediatric pulmonologist. Increased familiarity with these conditions allows for improved care of these patients by reducing time to diagnosis, tailoring management, and prompting further investigation into these disorders.

The Importance of Genetic Factors in the Management of Spontaneous Pneumothorax

Purpose of Review

Spontaneous pneumothoraces can be the presenting phenotype in a variety of different syndromic genetic conditions. Respiratory physicians therefore have the opportunity to diagnose and manage these patients early to prevent serious complications associated with these syndromes.

Recent Findings

The genetic syndromes that present with pneumothoraces can be split broadly between those resulting from defective extracellular matrix formation and those caused by defective tumour-suppressor pathways. When connective tissues are weakened, lifelong surveillance for arterial dilatation can be life-saving as surgical intervention is effective. Long-term aggressive treatment of blood pressure can also commence, although some controversy surrounds which drugs are most effective and precisely how these drugs modify disease progression. Rational treatments of syndromes in which tumour suppressor function is lost are being developed and, in some instances, can already be offered.

Summary

Careful clinical assessment of spontaneous pneumothorax may identify an underlying causal condition and facilitate life-saving intervention. Respiratory physicians must therefore be aware of these diseases and their diagnostic criteria.

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.

Birt-Hogg-Dubé syndrome presenting with spontaneous pneumothorax and extensive pulmonary cysts in the absence of skin lesions or renal pathology

Birt-Hogg-Dubé (BHD) syndrome is an autosomal dominant condition which classically manifests with skin lesions such as fibrofolliculomas, pulmonary cysts that predispose to spontaneous pneumothorax and an increased risk of developing renal cell carcinoma. We describe the case of a patient who presented with a spontaneous pneumothorax on a background of multiple lung cysts, in the absence of cutaneous fibrofolliculomas and renal tumours. A germline mutation in the folliculin FLCN gene was subsequently identified, confirming BHD syndrome. Our case highlights the importance of considering a broad differential diagnosis for the cause of a spontaneous pneumothorax in the presence of unexplained cystic lung disease and emphasises the value of maintaining a high index of clinical suspicion for inherited causes of pneumothoraces.

The Genetics of Pneumothorax

A genetic influence on spontaneous pneumothoraces-those occurring without a traumatic or iatrogenic cause-is supported by several lines of evidence: 1) pneumothorax can cluster in families (i.e., familial spontaneous pneumothorax), 2) mutations in the FLCN gene have been found in both familial and sporadic cases, and 3) pneumothorax is a known complication of several genetic syndromes. Herein, we review known genetic contributions to both sporadic and familial pneumothorax. We summarize the pneumothorax-associated genetic syndromes, including Birt-Hogg-Dubé syndrome, Marfan syndrome, vascular (type IV) Ehlers-Danlos syndrome, alpha-1 antitrypsin deficiency, tuberous sclerosis complex/lymphangioleiomyomatosis, Loeys-Dietz syndrome, cystic fibrosis, homocystinuria, and cutis laxa, among others. At times, pneumothorax is their herald manifestation. These syndromes have serious potential extrapulmonary complications (e.g., malignant renal tumors in Birt-Hogg-Dubé syndrome), and surveillance and/or treatment is available for most disorders; thus, establishing a diagnosis is critical. To facilitate this, we provide an algorithm to guide the clinician in discerning which cases of spontaneous pneumothorax may have a genetic or familial contribution, which cases warrant genetic testing, and which cases should prompt an evaluation by a geneticist.