Pneumothorax after air travel in lymphangioleiomyomatosis, idiopathic pulmonary fibrosis, and sarcoidosis

Diffuse Cystic Lung Disease: A Clinical Guide to Recognition and Management

TOPIC IMPORTANCE

Diffuse cystic lung diseases (DCLDs) represent a group of pathophysiologically heterogeneous entities that share a common radiologic phenotype of multiple thin-walled pulmonary cysts. DCLDs differ from the typical fibroinflammatory interstitial lung diseases in their epidemiology, clinical presentation, molecular pathogenesis, and therapeutic approaches, making them worthy of a distinct classification. The importance of timely and accurate identification of DCLDs is heightened by the impact on patient management including recent discoveries of targeted therapeutic approaches for some disorders.

REVIEW FINDINGS

This article offers a practical framework for evaluating patients with DCLD, indicating the most appropriate and current diagnostic and management approaches. We focus on the DCLDs that are most likely to be encountered by practicing pulmonologists: lymphangioleiomyomatosis, pulmonary Langerhans cell histiocytosis, Birt-Hogg-Dubé syndrome, and lymphoid interstitial pneumonia. Chest CT scan is the most informative noninvasive diagnostic modality to identify DCLDs. Thereafter, instituting a structured approach to high-yield associated factors (eg, medical, social, and family history; renal and dermatologic findings) increases the likelihood of identifying DCLDs and achieving a diagnosis.

SUMMARY

Although the individual diseases that comprise the DCLD family are rare, taken together, DCLDs can be encountered more frequently in clinical practice than commonly perceived. An increased eagerness among general pulmonary physicians to recognize these entities, coupled with a practical and systematic clinical approach to examinations and investigations, is required to improve case findings, allow earlier intervention, and reduce morbidity and mortality.

Risk of pneumothorax in Birt-Hogg-Dubé syndrome during pregnancy and birth

Birt-Hogg-Dubé syndrome (BHDS) is a genetic disorder characterized by fibrofolliculomas, renal cell cancer and lung cysts. Patients are at risk to develop pneumothorax but the magnitude of this risk during pregnancy is unknown. Information was obtained from 46 women with BHDS that had at least one pregnancy (BHDS-with preg), 18 female BHDS relatives without pregnancies (BHDS-no preg) and 25 non-BHDS female relatives with at least one pregnancy (noBHDS-with preg). In total, 77 pneumothoraces occurred in the BHDS-with preg group (mean 1.7/patient) and 11 in the BHDS-no preg group. Comparison of patient years for the first two groups showed pneumothorax incidence rates of 0.054 and 0.016, respectively. The incidence rate difference was significant [0.038 (CI 0.02-0.057), value of p-value 0.0001]. This difference is not caused by an increased number of patients with pneumothorax but by an increased number of pneumothoraces per patient. Pregnancy in BHDS therefore might be a risk factor for multiple pneumothoraces.

French recommendations for the diagnosis and management of lymphangioleiomyomatosis

BACKGROUND

The present article is an English-language version of the French National Diagnostic and Care Protocol, a pragmatic tool to optimize and harmonize the diagnosis, care pathway, management and follow-up of lymphangioleiomyomatosis in France.

METHODS

Practical recommendations were developed in accordance with the method for developing a National Diagnosis and Care Protocol for rare diseases of the Haute Autorité de Santé and following international guidelines and literature on lymphangioleiomyomatosis. It was developed by a multidisciplinary group, with the help of patient representatives and of RespiFIL, the rare disease network on respiratory diseases.

RESULTS

Lymphangioleiomyomatosis is a rare lung disease characterised by a proliferation of smooth muscle cells that leads to the formation of multiple lung cysts. It occurs sporadically or as part of a genetic disease called tuberous sclerosis complex (TSC). The document addresses multiple aspects of the disease, to guide the clinicians regarding when to suspect a diagnosis of lymphangioleiomyomatosis, what to do in case of recurrent pneumothorax or angiomyolipomas, what investigations are needed to make the diagnosis of lymphangioleiomyomatosis, what the diagnostic criteria are for lymphangioleiomyomatosis, what the principles of management are, and how follow-up can be organised. Recommendations are made regarding the use of pharmaceutical specialties and treatment other than medications.

CONCLUSION

These recommendations are intended to guide the diagnosis and practical management of pulmonary lymphangioleiomyomatosis.

Underlying lung disease and exposure to terrestrial moderate and high altitude: personalised risk assessment

Once reserved for the fittest, worldwide altitude travel has become increasingly accessible for ageing and less fit people. As a result, more and more individuals with varying degrees of respiratory conditions wish to travel to altitude destinations. Exposure to a hypobaric hypoxic environment at altitude challenges the human body and leads to a series of physiological adaptive mechanisms. These changes, as well as general altitude related risks have been well described in healthy individuals. However, limited data are available on the risks faced by patients with pre-existing lung disease. A comprehensive literature search was conducted. First, we aimed in this review to evaluate health risks of moderate and high terrestrial altitude travel by patients with pre-existing lung disease, including chronic obstructive pulmonary disease, sleep apnoea syndrome, asthma, bullous or cystic lung disease, pulmonary hypertension and interstitial lung disease. Second, we seek to summarise for each underlying lung disease, a personalized pre-travel assessment as well as measures to prevent, monitor and mitigate worsening of underlying respiratory disease during travel.

Lymphangioleiomyomatosis: pathogenesis, clinical features, diagnosis, and management

Lymphangioleiomyomatosis (LAM) is a slowly progressive, low-grade, metastasising neoplasm of women, characterised by infiltration of the lung parenchyma with abnormal smooth muscle-like cells, resulting in cystic lung destruction. The invading cell in LAM arises from an unknown source and harbours mutations in tuberous sclerosis complex (TSC) genes that result in constitutive activation of the mechanistic target of rapamycin (mTOR) pathway, dysregulated cellular proliferation, and a programme of frustrated lymphangiogenesis, culminating in disordered lung remodelling and respiratory failure. Over the past two decades, all facets of LAM basic and clinical science have seen important advances, including improved understanding of molecular mechanisms, novel diagnostic and prognostic biomarkers, effective treatment strategies, and comprehensive clinical practice guidelines. Further research is needed to better understand the natural history of LAM; develop more powerful diagnostic, prognostic, and predictive biomarkers; optimise the use of inhibitors of mTOR complex 1 in the treatment of LAM; and explore novel approaches to the development of remission-inducing therapies.

Tuberous sclerosis complex for the pulmonologist

Tuberous sclerosis complex (TSC) is a rare multisystem genetic disorder affecting almost all organs with no sex predominance. TSC has an autosomal-dominant inheritance and is caused by a heterozygous mutation in either the TSC1 or TSC2 gene leading to hyperactivation of the mammalian target of rapamycin (mTOR). TSC is associated with several pulmonary manifestations including lymphangioleiomyomatosis (LAM), multifocal micronodular pneumocyte hyperplasia (MMPH) and chylous effusions. LAM is a multisystem disorder characterised by cystic destruction of lung parenchyma, and may occur in either the setting of TSC (TSC-LAM) or sporadically (S-LAM). LAM occurs in 30–40% of adult females with TSC at childbearing age and is considered a nonmalignant metastatic neoplasm of unknown origin. TSC-LAM is generally milder and, unlike S-LAM, may occur in males. It manifests as multiple, bilateral, diffuse and thin-walled cysts with normal intervening lung parenchyma on chest computed tomography. LAM is complicated by spontaneous pneumothoraces in up to 70% of patients, with a high recurrence rate. mTOR inhibitors are the treatment of choice for LAM with moderately impaired lung function or chylous effusion. MMPH, manifesting as multiple solid and ground-glass nodules on high-resolution computed tomography, is usually harmless with no need for treatment.

Tuberous sclerosis complex is associated with diverse pulmonary manifestations including LAM, multiple micronodular pneumocyte hyperplasia and chylous effusions. LAM occurs in 30–40% of adult females with tuberous sclerosis complex.https://bit.ly/3iLqZ08

Quantitative Analysis of Cystic Lung Diseases by Use of Paired Inspiratory and Expiratory CT: Estimation of the Extent of Cyst-Airway Communication and Evaluation of Diagnostic Utility

PURPOSE

To establish a method for quantitatively estimating the extent of the communication between the cyst and the airway in cystic lung diseases (CLDs) and evaluate its diagnostic utility in differentiating among CLDs.

MATERIALS AND METHODS

Seventy-one patients (mean age, 49.9 years; age range, 25-79 years) with CLDs who underwent paired inspiratory and expiratory CT between July 2015 and July 2018 were enrolled in this prospective study. Participants were divided into three groups based on their diagnosis: Birt-Hogg-Dubé syndrome (BHDS) group (15 participants), lymphangioleiomyomatosis (LAM) group (43 participants), and other diseases (OT) group (13 participants). Total lung volume (TLV) and low-attenuation area volume (LAAV) were calculated at inspiration and expiration. The collapsibility of the LAAV was determined as the expiration-to-inspiration (E/I) ratio of LAAV (E/I ratio LAAV). The cyst-airway communicating index (CACI), the ratio of the LAAV change between inspiration and expiration to the TLV change between inspiration and expiration, was also determined. Receiver operating characteristic (ROC) analysis was used to evaluate the diagnostic utility for differentiating diseases.

RESULTS

The E/I ratio LAAV was significantly higher in the BHDS group (0.69; 95% confidence interval [CI]: 0.61, 0.78) than in the LAM (0.33; 95% CI: 0.28, 0.38) (P < .001) and the OT (0.51; 95% CI: 0.38, 0.64) (P = .038) groups. The CACI was significantly lower in the BHDS group (0.89; 95% CI: 0.61, 1.17) than in the LAM (1.89; 95% CI: 1.76, 2.0) (P < .001) and the OT (1.539; 95% CI: 1.21, 1.86) (P = .003) groups. There was no significant difference in the area under the ROC curve of the CACI (0.881; 95% CI: 0.7749, 0.987) and the E/I ratio LAAV (0.877; 95% CI: 0.791, 0.963) for differentiating BHDS from other diseases.

CONCLUSION

Quantitative analysis using paired inspiratory and expiratory CT for estimating the extent of cyst-airway communication in CLDs is useful when distinguishing BHDS from other diseases.Supplemental material is available for this article.© RSNA, 2020See also the commentary by Chung in this issue.

Spontaneous pneumothorax and air travel in Pulmonary Langerhans cell histiocytosis: A patient survey

BACKGROUND

The optimal approach for management of spontaneous pneumothoraces (SPs) and the safety of air travel in patients with pulmonary Langerhans cell histiocytosis (PLCH) are not well established.

METHODS

Patients with PLCH were recruited from the Rare Lung Diseases Clinic Network and the Histiocytosis Association, and surveyed about disease manifestations and safety of air travel.

RESULTS

A total of 94 patients completed the survey. Median age at diagnosis of PLCH was 40 years (range: 15-67 years). Average interval between symptom onset and diagnosis was 2.9 years (range: -4 to 31 years). Twenty-two patients (23%) had at least one SP, of which 14 (64%) had at least one additional SP that showed either an ipsilateral recurrence (10 patients; 45%) or a contralateral recurrence (8 patients; 36%). Mean age at the time of first SP was 29 years. SP was the presenting manifestation that led to the diagnosis of PLCH in 19% of patients, typically after the second episode. Surgical pleurodesis reduced the recurrence rate of SP by half in comparison with conservative management (29% vs. 65%, p = 0.025). Two patients experienced an episode of SP during air travel, consistent with an air travel-related pneumothorax rate of 2.4% per patient and 0.27% per flight.

CONCLUSIONS

SP is a common manifestation of PLCH, can be seen in approximately one-fourth of the patients, and has a high recurrence risk. Surgical pleurodesis leads to a substantial reduction in the SP recurrence risk. The risk of an air travel-related SP in patients with PLCH is about 2-3 per thousand flights. TRIAL REGISTRY CLINICALTRIALS.GOV: NCT03052101.

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.

Differentiation Between Lymphangioleiomyomatosis and Birt-Hogg-Dubé Syndrome: Analysis of Pulmonary Cysts on CT Images

OBJECTIVE

The purposes of this study were to identify diagnostic imaging markers for differentiating pulmonary cysts in lymphangioleiomyomatosis and Birt-Hogg-Dubé syndrome and to identify potential risk factors for spontaneous pneumothorax in the two diseases.

MATERIALS AND METHODS

This retrospective study included 44 patients with lymphangioleiomyomatosis (44 women; mean age, 35 ± 10.9 years) and 13 patients with Birt-Hogg-Dubé syndrome (nine men, four women; mean age, 45.1 ± 10.9 years). CT findings were analyzed to determine the shape; presence of septation, wall visibility, and subpleural cysts; size; number; distribution; location of the largest cyst; and presence of cysts encircling the bronchovascular bundle ("air-cuff" sign) and of mediastinal fat indentation. Multiple logistic regression was performed to identify risk factors for spontaneous pneumothorax.

RESULTS

Compared with patients with lymphangioleiomyomatosis, patients with Birt-Hogg-Dubé syndrome were significantly older, and more of them were men. The cysts in these patients had a more irregular shape, more septation, lower and more peripheral distribution, larger maximum size, and more attachment to the pleura, air-cuff sign, indentation on mediastinal fat, and subpleural cysts larger than 2 cm. The maximum diameter of cysts was the sole independent risk factor for spontaneous pneumothorax (p = 0.027; 95% CI, 1.043-1.992) in both diseases. ROC analysis showed an AUC of 0.745 (95% CI, 0.612-0.851), and the optimal cutoff value was 22 mm (sensitivity, 72.5%; specificity, 76.5%).

CONCLUSION

Several CT imaging markers may help in differentiating pulmonary cysts in patients with lymphangioleiomyomatosis and those with Birt-Hogg-Dubé syndrome and in predicting spontaneous pneumothorax.

Air travel and incidence of pneumothorax in lymphangioleiomyomatosis

BACKGROUND

Pulmonary lymphangioleiomyomatosis (LAM) is a rare disease of women characterized by multiple lung cysts leading to respiratory insufficiency and frequent pneumothorax (PT). Air travel (AT) could increase the risk of PT in LAM through rupture of subpleural cysts induced by atmospheric pressure changes in aircraft cabin. To determine whether AT increases the risk of PT in LAM, we performed a retrospective survey of members of European LAM patient associations. A flight-related PT was defined as occurring ≤30 days after AT.

RESULTS

145 women reported 207 PT. In 128 patients with available data, the annual incidence of PT was 8% since the first symptoms of LAM and 5% since LAM diagnosis, compared to 0.006% in the general female population. Following surgical or chemical pleurodesis, the probability of remaining free of PT recurrence was respectively 82, 68, and 59% after 1, 5 and 10 years, as compared to only 55, 46 and 39% without pleurodesis (p = 0.026). 70 patients with available data performed 178 AT. 6 flight-related PT occurred in 5 patients. PT incidence since first symptoms of LAM was significantly higher ≤30 days after AT as compared to non-flight periods (22 versus 6%, risk ratio 3.58, confidence interval 1.40-7.45).

CONCLUSIONS

The incidence of PT in LAM is about 1000 times higher than in the general female population, and is further increased threefold after AT. Chemical or surgical pleurodesis partly reduces the risk of PT recurrence in LAM.

Pulmonary manifestations in tuberous sclerosis complex

Tuberous sclerosis complex has manifestations in many organ systems, including brain, heart, kidney, skin, and lung. The primary manifestations in the lung are lymphangioleiomyomatosis (LAM) and multifocal micronodular pneumocyte hyperplasia (MMPH). LAM affects almost exclusively women, and causes cystic lung destruction, pneumothorax, and chylous pleural effusions. LAM can lead to dyspnea, oxygen dependence, and respiratory failure, with more rapid disease progression during the premenopausal years. In contrast, MMPH affects men and women equally, causing small nodular pulmonary deposits of type II pneumocytes that rarely progress to symptomatic disease. Here, we review the clinical features and pathogenesis of LAM and MMPH.

Recent advances in the management of lymphangioleiomyomatosis

Lymphangioleiomyomatosis is a rare disorder that predominantly affects women and is characterized by progressive cystic changes in the lung, leading to gradually worsening shortness of breath and lung function impairment. Pleural complications such as pneumothorax and chylothorax commonly occur in these patients. Lymphangioleiomyomatosis can occur as a form of lung involvement in tuberous sclerosis complex or as a sporadic form (without tuberous sclerosis complex). Etiology in both forms of this disease centers on mutations in the tuberous sclerosis genes. Advances in our understanding of the regulatory role of tuberous sclerosis gene products (hamartin/tuberin) in the mechanistic target of rapamycin (mTOR) signaling pathway have led to the identification of effective therapy (mTOR inhibitors) for a rare disorder, once considered uniformly fatal. Here, we summarize the evolution of current concepts regarding lymphangioleiomyomatosis with an emphasis on recent advances and unresolved issues.

Air Travel-Related Spontaneous Pneumothorax in Diffuse Cystic Lung Diseases

Purpose of review

Spontaneous pneumothorax (SP) is a common manifestation of patients with diffuse cystic lung diseases (DCLDs) such as lymphangieoleiomyomatosis (LAM), pulmonary Langerhans cell histiocytosis (PLCH) and Birt-Hogg-Dubé syndrome (BHD). Air travel may pose an additional risk for the development of SP. Here, we summarize the literature pertaining to air travel related SP in DCLDs in order to assist patients and clinicians in appropriate decision-making with regards to air travel.

Recent Findings

Several recent studies have estimated that the per-flight risk of SP in patients with DCLDs is approximately 1%, with disease-specific risk estimates of 1.1-2.6% in LAM, 0-0.63% in BHD, and 0.37% in PLCH.

Summary

In general, it should be safe for most patients with DCLDs to undertake air travel. Patients should be counseled to seek medical attention and not board the airplane in the presence of sudden/new onset chest pain and/or dyspnea prior to boarding the plane.

Spontaneous Pneumothoraces in Patients with Birt-Hogg-Dubé Syndrome

RATIONALE

Spontaneous pneumothorax is a common complication of Birt-Hogg-Dubé syndrome (BHD).

OBJECTIVES

The optimal approach to treatment and prevention of BHD-associated spontaneous pneumothorax, and to advising patients with BHD regarding risk of pneumothorax associated with air travel, is not well established.

METHODS

Patients with BHD were recruited from the Rare Lung Diseases Clinic Network and the BHD Foundation and surveyed about disease manifestations and air travel experiences.

RESULTS

A total of 104 patients completed the survey. The average age at diagnosis was 47 years, with an average delay from first symptoms of 13 years. Pulmonary cysts were the most frequent phenotypic manifestation of BHD, present in 85% of patients. Spontaneous pneumothorax was the presenting manifestation that led to the diagnosis of BHD in 65% of patients, typically after the second episode (mean, 2.4 episodes). Seventy-nine (76%) of 104 patients had at least one spontaneous pneumothorax during their lifetime, and 82% had multiple pneumothoraces. Among patients with multiple pneumothoraces, 73% had an ipsilateral recurrence, and 48% had a subsequent contralateral spontaneous pneumothorax following a sentinel event. The mean ages at first and second pneumothoraces were 36.5 years (range, 14-63 yr) and 37 years (range, 20-55 yr), respectively. The average number of spontaneous pneumothoraces experienced by patients with a sentinel pneumothorax was 3.6. Pleurodesis was generally performed after the second (mean, 2.4) ipsilateral pneumothorax and reduced the ipsilateral recurrence rate by half. A total of 11 episodes of spontaneous pneumothorax occurred among eight patients either during or within the 24-hour period following air travel, consistent with an air travel-related pneumothorax rate of 8% per patient and 0.12% per flight. Prior pleurodesis reduced the occurrence of a subsequent flight-related pneumothorax.

CONCLUSIONS

Spontaneous pneumothorax is an important, recurrent manifestation of pulmonary involvement in patients with BHD, and pleurodesis should be considered following the initial pneumothorax to reduce the risk of recurrent episodes. In general, in patients with BHD, pneumothorax occurs in about 1-2 per 1,000 flights, and the risk is lower among patients with a history of prior pleurodesis.

Spontaneous pneumothorax in diffuse cystic lung diseases

PURPOSE OF REVIEW

Diffuse cystic lung diseases (DCLDs) are a heterogeneous group of disorders with varying pathophysiologic mechanisms that are characterized by the presence of air-filled lung cysts. These cysts are prone to rupture, leading to the development of recurrent spontaneous pneumothoraces. In this article, we review the epidemiology, clinical features, and management DCLD-associated spontaneous pneumothorax, with a focus on lymphangioleiomyomatosis, Birt-Hogg-Dubé syndrome, and pulmonary Langerhans cell histiocytosis.

RECENT FINDINGS

DCLDs are responsible for approximately 10% of apparent primary spontaneous pneumothoraces. Computed tomography screening for DCLDs (Birt-Hogg-Dubé syndrome, lymphangioleiomyomatosis, and pulmonary Langerhans cell histiocytosis) following the first spontaneous pneumothorax has recently been shown to be cost-effective and can help facilitate early diagnosis of the underlying disorders. Patients with DCLD-associated spontaneous pneumothorax have a very high rate of recurrence, and thus pleurodesis should be considered following the first episode of spontaneous pneumothorax in these patients, rather than waiting for a recurrent episode. Prior pleurodesis is not a contraindication to future lung transplant.

SUMMARY

Although DCLDs are uncommon, spontaneous pneumothorax is often the sentinel event that provides an opportunity for diagnosis. By understanding the burden and implications of pneumothoraces in DCLDs, clinicians can facilitate early diagnosis and appropriate management of the underlying disorders.

Air Repatriation With a Medium-sized Pneumothorax Without Thoracic Tube: A Special Case of a Repatriation Accompanied by an Experienced Surgeon

We report on the repatriation of a 28-year old female from Germany, who was involved in a serious bus accident and was transported to the nearest hospital in Oruro, Bolivia. CT scans and x-rays performed in this hospital demonstrated a complete pneumothorax right. Thorax drainage was inserted, which was removed after 5 days. Since the hospital refused to acknowledge the presence of a residual middle-sized pneumothorax on the repatriation day and did not want to insert another tube, the decision was made to repatriate the patient on commercial flight back home to Germany without a thoracic tube.

Risk of spontaneous pneumothorax due to air travel and diving in patients with Birt-Hogg-Dubé syndrome

Background and objectives

Birt–Hogg–Dubé syndrome is an autosomal dominant disorder characterized by skin fibrofolliculomas, lung cysts, spontaneous pneumothorax and renal cell cancer due to germline folliculin (FLCN) mutations (Menko et al. in Lancet Oncol 10(12):1199–1206, 2009). The aim of this study was to evaluate the incidence of spontaneous pneumothorax in patients with BHD during or shortly after air travel and diving.

Methods

A questionnaire was sent to a cohort of 190 BHD patients and the medical files of these patients were evaluated. The diagnosis of BHD was confirmed by FLCN mutations analysis in all patients. We assessed how many spontaneous pneumothoraces (SP) occurred within 1 month after air travel or diving.

Results

In total 158 (83.2 %) patients returned the completed questionnaire. A total of 145 patients had a history of air travel. Sixty-one of them had a history of SP (42.1 %), with a mean of 2.48 episodes (range 1–10). Twenty-four (35.8 %) patients had a history of pneumothorax on both sides. Thirteen patients developed SP < 1 month after air travel (9.0 %) and two patients developed a SP < 1 month after diving (3.7 %). We found in this population of BHD patients a pneumothorax risk of 0.63 % per flight and a risk of 0.33 % per episode of diving. Symptoms possible related to SP were perceived in 30 patients (20.7 %) after air travel, respectively in ten patients (18.5 %) after diving.

Conclusion

Based on the results presented in this retrospective study, exposure of BHD patients to considerable changes in atmospheric pressure associated with flying and diving may be related to an increased risk for developing a symptomatic pneumothorax. Symptoms reported during or shortly after flying and diving might be related to the early phase of pneumothorax. An individualized advice should be given, taking also into account patients’ preferences and needs.

Pneumothorax in cystic fibrosis: beyond the guidelines

Pneumothorax is a serious but common complication in patients with cystic fibrosis (CF). It has adverse prognostic implications as well as associations with subsequent reduction in lung function and significant risk of recurrence. Management dilemmas frequently occur that are beyond current guidelines. We review the evidence and highlight management difficulties in pneumothoraces in CF.

Incidence of Pneumothorax in Patients With Lymphangioleiomyomatosis Undergoing Pulmonary Function and Exercise Testing

Because pneumothorax is frequent in lymphangioleiomyomatosis, patients have expressed concerns regarding the risk of pneumothorax associated with pulmonary function or exercise testing. Indeed, pneumothorax has been reported in patients with lung disease after both of these tests. The aim of this study was to determine the incidence of pneumothorax in patients with lymphangioleiomyomatosis during admissions to the National Institutes of Health Clinical Research Center between 1995 and 2015. Medical records were reviewed to identify patients who had a pneumothorax during their stay at the National Institutes of Health. A total of 691 patients underwent 4,523 pulmonary function tests and 1,900 exercise tests. Three patients developed pneumothorax after pulmonary function tests and/or exercise tests. The incidence of pneumothorax associated with lung function testing was 0.14 to 0.29 of 100 patients or 0.02 to 0.04 of 100 tests. The incidence of pneumothorax in patients undergoing exercise testing was 0.14 to 0.28 of 100 patients or 0.05 to 0.10 of 100 tests. The risk of pneumothorax associated with pulmonary function or exercise testing in patients with lymphangioleiomyomatosis is low.

Women with TSC: Relationship between Clinical, Lung Function and Radiological Features in a Genotyped Population Investigated for Lymphangioleiomyomatosis

The advent of pharmacological therapies for lymphangioleiomyomatosis (LAM) has made early diagnosis important in women with tuberous sclerosis complex (TSC), although the lifelong cumulative radiation exposure caused by chest computer tomography (CT) should not be underestimated. We retrospectively investigated, in a cohort of TSC outpatients of San Paolo Hospital (Milan, Italy) 1) the role of pulmonary function tests (PFTs) for LAM diagnosis, 2) the association between LAM and other features of TSC (e.g. demography, extrapulmonary manifestations, genetic mutations, etc.), and 3) the characteristics of patients with multifocal micronodular pneumocyte hyperplasia (MMPH). Eighty-six women underwent chest CT scan; pulmonary involvement was found in 66 patients (77%; 49% LAM with or without MMPH, and 28% MMPH alone). LAM patients were older, with a higher rate of pneumothorax, presented more frequently with renal and hepatic angiomyolipomas, and tended to have a TSC2 mutation profile. PFTs, assessed in 64% of women unaffected by cognitive impairments, revealed a lower lung diffusion capacity in LAM patients. In multivariate analysis, age, but not PFTs, resulted independently associated with LAM diagnosis. Patients with MMPH alone did not show specific clinical, functional or genetic features. A mild respiratory impairment was most common in LAM-TSC patients: In conclusions, PFTs, even if indicated to assess impairment in lung function, are feasible in a limited number of patients, and are not significantly useful for LAM diagnosis in women with TSC.

Mammalian Target of Rapamycin Inhibitors and Life-Threatening Conditions in Tuberous Sclerosis Complex

Tuberous sclerosis complex (TSC) is a multisystem disease associated with an overall reduction in life expectancy due to the possible occurrence of different life-threatening conditions. Subjects affected by TSC are, in fact, at risk of hydrocephalus secondary to the growth of subependymal giant cell astrocytomas, or of sudden unexpected death in epilepsy. Other nonneurological life-threatening conditions include abdominal bleeding owing to renal angiomyolipomas rupture, renal insufficiency due to progressive parenchymal destruction by multiple cysts, pulmonary complications due to lymphangioleiomyomatosis, and cardiac failure or arrhythmias secondary to rhabdomyomas. In the last decades, there has been a great progress in understanding the pathophysiology of TSC-related manifestations, which are mainly linked to the hyperactivation of the so-called mammalian target of rapamycin (mTOR) pathway, as a consequence of the mutation in 1 of the 2 genes TSC1 or TSC2. This led to the development of new treatment strategies for this disease. In fact, it is now available as a biologically targeted therapy with everolimus, a selective mTOR inhibitor, which has been licensed in Europe and USA for the treatment of subependymal giant cell astrocytomas and angiomyolipomas in subjects with TSC. This drug also proved to benefit other TSC-related manifestations, including pulmonary lymphangioleiomyomatosis, cardiac rhabdomyomas, and presumably epileptic seizures. mTOR inhibitors are thus proving to be a systemic therapy able to simultaneously address different and potentially life-threatening complications, giving the hope of improving life expectation in individuals with TSC.

[Pulmonary lymphangioleiomyomatosis: From pathogenesis to management]

INTRODUCTION

Pulmonary lymphangioleiomyomatosis (LAM) is a rare disease affecting mainly young women.

BACKGROUND

The respiratory manifestations are characterized by a progressive cystic destruction of the lung parenchyma. Extrapulmonary involvement includes benign renal tumours called angiomyolipomas and abdominal lymphatic masses called lymphangioleiomyomas. At the pathological level, the cellular proliferation found in LAM is in part due to the presence of mutations in the tumour suppressor genes TSC1 and TSC2 (Tuberous Sclerosis Complex). These mutations lead to the activation of the mTOR pathway, which is currently the main therapeutic target. mTOR inhibitors such as sirolimus or everolimus have shown a beneficial effect on the decline in pulmonary function and a reduction of angiomyolipoma size, but are necessary in only some patients.

PERSPECTIVES

LAM cells have migratory properties mediated by the formation of new lymphatic vessels. They are also able to secrete metalloproteases, which enhance their invasiveness. Moreover, the expression of estrogen and progesterone receptors by LAM cells suggests a possible role for sex hormones in the pathogenesis of the disease.

CONCLUSION

A better understanding of mTOR-independent mechanisms would allow the development of novel therapeutic approaches.

Diffuse Cystic Lung Disease. Part I

The diffuse cystic lung diseases (DCLDs) are a group of pathophysiologically heterogenous processes that are characterized by the presence of multiple spherical or irregularly shaped, thin-walled, air-filled spaces within the pulmonary parenchyma. Although the mechanisms of cyst formation remain incompletely defined for all DCLDs, in most cases lung remodeling associated with inflammatory or infiltrative processes results in displacement, destruction, or replacement of alveolar septa, distal airways, and small vessels within the secondary lobules of the lung. The DCLDs can be broadly classified according to underlying etiology as those caused by low-grade or high-grade metastasizing neoplasms, polyclonal or monoclonal lymphoproliferative disorders, infections, interstitial lung diseases, smoking, and congenital or developmental defects. In the first of a two-part series, we present an overview of the cystic lung diseases caused by neoplasms, infections, smoking-related diseases, and interstitial lung diseases, with a focus on lymphangioleiomyomatosis and pulmonary Langerhans cell histiocytosis.

Management of lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM), a multisystem disease affecting almost exclusively women, is characterized by cystic lung destruction and presents with dyspnea, recurrent pneumothoraxes, chylous effusions, lymphangioleiomyomas, and angiomyolipomas. It is caused by the proliferation of a cancer-like LAM cell that possesses a mutation in either the tuberous sclerosis complex (TSC)1 or TSC2 genes. This article reviews current therapies and new potential treatments that are currently undergoing investigation. The major development in the treatment of LAM is the discovery of two mammalian target of rapamycin (mTOR) inhibitors, sirolimus and everolimus, as effective drugs. However, inhibition of mTOR increases autophagy, which may lead to enhanced LAM cell survival. Use of autophagy inhibitors, for example, hydroxychloroquine, in combination with sirolimus is now the subject of an ongoing drug trial (SAIL trial). Another consequence of mTOR inhibition by sirolimus is an increase in Rho activity, resulting in reduced programmed cell death. From these data, the concept evolved that a combination of sirolimus with disruption of Rho activity with statins (e.g. simvastatin) may increase TSC-null cell death and reduce LAM cell survival. A combined trial of sirolimus with simvastatin is under investigation (SOS trial). Since LAM occurs primarily in women and TSC-null cell survival and tumor growth is promoted by estrogens, the inhibition of aromatase to block estrogen synthesis is currently undergoing study (TRAIL trial). Other targets, for example, estrogen receptors, mitogen-activated protein kinase inhibitors, vascular endothelial growth factor-D signaling pathway, and Src kinase, are also being studied in experimental model systems. As in the case of cancer, combination therapy may become the treatment of choice for LAM.

Unusual causes of pneumothorax

Pneumothorax is divided to primary and secondary. It is a situation that requires immediate treatment, otherwise it could have severe health consequences. Pneumothorax can be treated either by thoracic surgeons, or pulmonary physicians. In our current work, we will focus on unusual cases of pneumothorax. We will provide the etiology and treatment for each case, also a discussion will be made for each situation.

Air travel and pneumothorax

The number of medical emergencies onboard aircraft is increasing as commercial air traffic increases and the general population ages, becomes more mobile, and includes individuals with serious medical conditions. Travelers with respiratory diseases are at particular risk for in-flight events because exposure to lower atmospheric pressure in a pressurized cabin at cruising altitude may result in not only hypoxemia but also pneumothorax due to gas expansion within enclosed pulmonary parenchymal spaces based on Boyle's law. Risks of pneumothorax during air travel pertain particularly to those patients with cystic lung diseases, recent pneumothorax or thoracic surgery, and chronic pneumothorax. Currently available guidelines are admittedly based on sparse data and include recommendations to delay air travel for 1 to 3 weeks after thoracic surgery or resolution of the pneumothorax. One of these guidelines declares existing pneumothorax to be an absolute contraindication to air travel although there are reports of uneventful air travel for those with chronic stable pneumothorax. In this article, we review the available data regarding pneumothorax and air travel that consist mostly of case reports and retrospective surveys. There is clearly a need for additional data that will inform decisions regarding air travel for patients at risk for pneumothorax, including those with recent thoracic surgery and transthoracic needle biopsy.

Commercial air travel after pneumothorax: a review of the literature

Because of the physiological stresses of commercial air travel, the presence of a pneumothorax has long been felt to be an absolute contraindication to flight. Additionally, most medical societies recommend that patients wait at least 2 weeks after radiographic resolution of the pneumothorax before they attempt to travel in a nonurgent fashion via commercial air transport. This review sought to survey the current body of literature on this topic to determine if a medical consensus exists; furthermore, this review considered the scientific support, if any, supporting these recommendations. In this review, we found a paucity of data on the issue and noted only a handful of prospective and retrospective studies; thus, true evidence-based recommendations are difficult to develop at this time. We have made recommendations, when possible, addressing the nonurgent commercial air travel for the patient with a recent pneumothorax. However, more scientific research is necessary in order to reach an evidence-based conclusion on pneumothoraces and flying.

The natural history of lymphangioleiomyomatosis: markers of severity, rate of progression and prognosis

Lymphangioleiomyomatosis (LAM) is a multisystem disease of women, characterized by proliferation of abnormal smooth muscle-like cells (LAM cells) that can metastasize, leading to the formation of lung cysts, fluid-filled cystic structures in the axial lymphatics (e.g., lymphangioleiomyomas), and angiomyolipomas, benign tumors usually involving the kidneys, comprising LAM cells and adipocytes, intermixed with incompletely developed vascular structures. LAM occurs sporadically or in association with tuberous sclerosis complex, an autosomal dominant syndrome characterized by hamartoma-like tumor growths. LAM may present with progressive dyspnea, recurrent pneumothorax, chylothorax, or abdominal hemorrhage. Computed tomography scans show thin-walled cysts scattered throughout the lungs, abdominal angiomyolipomas, and lymphangioleiomyomas. Pulmonary function tests show reduced flow rates (FEV(1)) and diffusion capacity (DL(CO)). Exercise testing may reveal gas exchange abnormalities, ventilatory limitation, and hypoxemia, which can occur with near-normal lung function. Methods used to grade the severity of disease are the LAM histology score, semiquantitative and quantitative computer tomography, pulmonary function testing, and cardiopulmonary exercise testing. Currently, progression of disease is best assessed by serial measurements of FEV(1), DL(CO), and exercise performance. New quantitative radiographic techniques that may offer advantages over physiologic testing are now available. Several potential biomarkers, such as LAM cells in peripheral blood, urine, and chyle and chemokines, vascular endothelial growth factors, and matrix metalloproteinases, may be useful as diagnostic tools or markers of organ involvement, disease severity, and progression.

[Is there a doctor on board?]

Medical problems during flight have become an important issue as the number of passengers and of miles flown continue to rise. Cabin pressurization causes hypoxia, hypobaria and decreased humidity, which are responsible for most medical incidents occurring during flight. Worldwide daily medical incidents are estimated at 350, i.e., one per 14,000 to 39,600 passengers. Medical advice is obtained in 69% of cases, from physicians (40%), nurses (25%), or paramedics (4%) on board the plane. The leading causes of medical incidents are gastrointestinal (25%), cardiac (10%), and neurological (10%) diseases. The incidence of cardiac arrest in flight is 1000 cases a year, worldwide. Since 1992, airlines have progressively equipped their planes with automated external defibrillators, and crew members are trained to use them. Passenger flights carry medical equipment and drugs, determined according to number of passengers and the flight distance. The conditions of intervention are codified: "good Samaritan" laws protect professionals from liability when they choose to aid others who are injured or ill. Current recommendations call for physicians to identify themselves, request an interpreter when necessary, obtain the patient's consent, conduct out examination, inform the patient, family members and crew members of the situation, contact ground medical staff, use well-known procedures, consider flight diversion, and write up a case report.

Therapeutic options for lymphangioleiomyomatosis (LAM): where we are and where we are going

Lymphangioleiomyomatosis (LAM), a multisystem disease affecting predominantly premenopausal and middle-aged women, causes progressive respiratory failure due to cystic lung destruction and is associated with lymphatic and kidney tumors. In the past, the treatment of LAM comprised exclusively anti-estrogen and related hormonal therapies. These treatments, however, have not been proven effective. In this article, we discuss new findings regarding the molecular mechanisms involved in the regulation of LAM cell growth, which may offer opportunities to develop effective and targeted therapeutic agents.

[Lymphangioleiomyomatosis]

Lymphangioleiomyomatosis is a rare pulmonary disease encountered almost exclusively in women of reproductive age. Pulmonary involvement is characterized by multiple thin-walled cysts in the lungs, recurrent pneumothorax, obstructive lung disorders, and progression to chronic respiratory failure over a mean period of 10 years. Certainty of diagnosis requires a lung biopsy, but international criteria have been proposed for a diagnosis without such a biopsy. International recommendations were recently issued for the diagnosis and treatment of lymphangioleiomyomatosis. Treatment is principally symptomatic and relies on the management of bronchial obstruction by bronchodilators; of hypoxemia by oxygen therapy; of pleural complications by pleurodesis, most often surgical; and of renal angiomyolipomas by percutaneous embolization in cases of hemorrhagic risk. Hormone treatment is not recommended. Hopes are high for mTor inhibitors (sirolimus and everolimus) and treatment trials are currently underway. Lung transplantation must be considered when chronic respiratory failure occurs in patients younger than 60 years.