Pleuropulmonary pathology of Birt-Hogg-Dubé syndrome

Pulmonary Cystic Disease and Its Mimics

Cystic diseases of the lung encompass a fairly broad variety of different diseases with causes including genetic abnormalities, smoking-related problems, developmental disorders, malignant neoplasms, and inflammatory processes. In addition, there are several diagnoses that closely resemble cystic lung disease, including cavitary diseases, cystic bronchiectasis, emphysema, and cystic changes in fibrosing interstitial lung disease. This article provides a review of cystic lung disease and its gross and histologic mimics.

Birt-Hogg-Dubé syndrome

Birt–Hogg–Dubé syndrome (BHD) is a rare inherited autosomal dominant disorder caused by germline mutations in the tumour suppressor gene FLCN, encoding the protein folliculin. Its clinical expression typically includes multiple pulmonary cysts, recurrent spontaneous pneumothoraces, cutaneous fibrofolliculomas and renal tumours of various histological types. BHD has no sex predilection and tends to manifest in the third or fourth decade of life. Multiple bilateral pulmonary cysts are found on chest computed tomography in >80% of patients and more than half experience one or more episodes of pneumothorax. A family history of pneumothorax is an important clue, which suggests the diagnosis of BHD. Unlike other cystic lung diseases such as lymphangioleiomyomatosis and pulmonary Langerhans cell histiocytosis, BHD does not lead to progressive loss of lung function and chronic respiratory insufficiency. Renal tumours affect about 30% of patients during their lifetime, and can be multiple and recurrent. The diagnosis of BHD is based on a combination of genetic, clinical and/or skin histopathological criteria. Management mainly consists of early pleurodesis in the case of pneumothorax, periodic renal imaging for tumour detection, and diagnostic work-up in search of BHD in relatives of the index patient.

Birt–Hogg–Dubé syndrome is a rare genetic disorder characterised by multiple lung cysts, recurrent pneumothoraces, skin lesions and kidney tumours. As the presenting symptoms may be respiratory, chest physicians should be able to identify this disease.https://bit.ly/2xsOTuk

Genetic Risk Factors for Spontaneous Pneumothorax in Birt-Hogg-Dubé Syndrome

BACKGROUND

Birt-Hogg-Dubé syndrome (BHDS) is a genetic tumor syndrome characterized by lung cysts, spontaneous pneumothorax, fibrofolliculomas, and renal cell cancer. Because of its rarity and clinical heterogeneity, much is still unknown regarding the course of the disease and individual risk assessment. Therefore, we studied nonenvironmental risk factors for pneumothorax in a large sample of patients with BHDS.

METHODS

Clinical data were available from 197 patients with BHDS (male patients, 103; female patients, 94) belonging to 63 unrelated families. The FLCN coding region including adjacent intronic sequences was analyzed by PCR and subsequent Sanger sequencing as well as by multiplex ligation-dependent probe amplification. Statistical analyses were performed, using adequate methods to account for familial clustering.

RESULTS

Patients who had only a single spontaneous pneumothorax were significantly older at the time of occurrence than those with multiple pneumothoraces (mean, 38.93 vs 29.74 years; P value, .010). The risk for three or more pneumothoraces drastically increased after the second event. Significantly increased pneumothorax risks were found for mutations c.1300G>C (59%) and c.250-2A>G (77%), compared with FLCN hotspot mutation c.1285dup (37% risk) (P value, .02).

CONCLUSIONS

We observed significant differences for the spontaneous pneumothorax risk regarding both age and sex in patients with BHDS. Furthermore, two FLCN mutations were identified that are associated with significantly increased pneumothorax risk. Thus, formerly unknown individual predictors have been identified that provide improved risk stratification for patients with BHDS.

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.

Pathology of Birt-Hogg-Dubé syndrome: A special reference of pulmonary manifestations in a Japanese population with a comprehensive analysis and review

Birt-Hogg-Dubé (BHD) syndrome is a rare genetic disorder characterized by cutaneous fibrofolliculomas, pulmonary cysts and renal cell carcinomas. Affected individuals inherit germline mutations in the folliculin gene (FLCN). Approximately 150 pathogenic FLCN variants have been identified worldwide. Many Japanese probands of BHD syndrome were first identified by pulmonologists and/or radiologists during treatment of pneumothoraces. Lung specimens obtained through video-assisted thoracoscopic surgery (VATS) have characteristic features unique to BHD syndrome; however, pathologists often miss key findings and diagnose patients with "bullae/blebs". The pleural and subpleural cysts of BHD syndrome-associated lung diseases are often modified by tissue remodeling and can be difficult to distinguish from emphysematous bullae/blebs. Intraparenchymal unruptured cysts tend to retain distinctive features that are different from other cystic lung diseases. Here, we review the clinicopathological findings of BHD syndrome in a Japanese population based on data from 200 probands diagnosed by genetic testing and a total of 520 symptomatic family members identified through BHD-NET Japan (http://www.bhd-net.jp/). Detailed morphology of pulmonary cysts obtained from VATS and autopsied lung specimens are described, and pathological clues for differentiating miscellaneous cystic lung disorders are discussed.

The ABCs of BHD: An In-Depth Review of Birt-Hogg-Dubé Syndrome

OBJECTIVE

Birt-Hogg-Dubé (BHD) syndrome is an autosomal dominant inherited syndrome involving multiple organs. In young patients, renal neoplasms that are multiple, bilateral, or both, such as oncocytomas, chromophobe renal cell carcinoma (RCC), hybrid chromophobe RCC-oncocytomas, clear cell RCC, and papillary RCC, can suggest BHD syndrome. Extrarenal findings, including dermal lesions, pulmonary cysts, and spontaneous pneumothoraces, also aid in diagnosis.

CONCLUSION

Radiologists may be one of the first medical specialists to suggest the diagnosis of BHD syndrome. Knowledge of pathogenesis and management, including the importance of the types of renal neoplasms in a given patient, is needed to properly recognize this rare condition.

Birt-Hogg-Dube syndrome accompanied by pulmonary arteriovenous malformation

A 25-year-old male with Birt-Hogg-Dube (BHD) syndrome who developed hemothorax caused by ruptured of pulmonary arteriovenous malformation was reported. The patient was admitted to the hospital due to chest pain. A chest X-ray showed pleural fluid in his left lung, and a chest CT showed the presence of a tumor with enhanced contrast in the lower left lobe of approximately 5 cm in a diameter. Pleural fluid was collected by tap and indicated the presence of blood; therefore, hemothorax was suspected. Thoracoscopic surgery was performed to remove the mass for homostasis. Pathological findings indicated that the resected tumor-like lesion was an intrapulmonary hematoma, and aggregated vascular vessels of various diameters forming incomplete media elastic lamina was observed around the hematoma; therefore, it was diagnosed as pulmonary arteriovenous malformation. Family history of the patient indicated the presence of pneumothorax and malignant diseases, and the patient presented with papules and multiple pulmonary cysts. The genetic test revealed a deletion of exon 11 of the BHD gene; therefore, the patient was diagnosed with BHD syndrome. This report is the first to describe BHD syndrome accompanied by pulmonary arteriovenous malformation.

Pulmonary Neoplasms in Patients with Birt-Hogg-Dubé Syndrome: Histopathological Features and Genetic and Somatic Events

Birt-Hogg-Dubé syndrome (BHD) is an inherited disorder caused by genetic mutations in the folliculin (FLCN) gene. Individuals with BHD have multiple pulmonary cysts and are at a high risk for developing renal cell carcinomas (RCCs). Currently, little information is available about whether pulmonary cysts are absolutely benign or if the lungs are at an increased risk for developing neoplasms. Herein, we describe 14 pulmonary neoplastic lesions in 7 patients with BHD. All patients were confirmed to have germline FLCN mutations. Neoplasm histologies included adenocarcinoma in situ (n = 2), minimally invasive adenocarcinoma (n = 1), papillary adenocarcinoma (n = 1), micropapillary adenocarcinoma (n = 1), atypical adenomatous hyperplasia (n = 8), and micronodular pneumocyte hyperplasia (MPH)-like lesion (n = 1). Five of the six adenocarcinoma/MPH-like lesions (83.3%) demonstrated a loss of heterozygosity (LOH) of FLCN. All of these lesions lacked mutant alleles and preserved wild-type alleles. Three invasive adenocarcinomas possessed additional somatic events: 2 had a somatic mutation in the epidermal growth factor receptor gene (EGFR) and another had a somatic mutation in KRAS. Immunohistochemical analysis revealed that most of the lesions were immunostained for phospho-mammalian target of rapamycin (p-mTOR) and phospho-S6. Collective data indicated that pulmonary neoplasms of peripheral adenocarcinomatous lineage in BHD patients frequently exhibit LOH of FLCN with mTOR pathway signaling. Additional driver gene mutations were detected only in invasive cases, suggesting that FLCN LOH may be an underlying abnormality that cooperates with major driver gene mutations in the progression of pulmonary adenocarcinomas in BHD patients.

Recurrent spontaneous pneumothoraces and bullous emphysema. A novel mutation causing Birt-Hogg-Dube syndrome

Birt-Hogg-Dube syndrome (BHDS) is a rare form of classically cystic lung disease that may present with spontaneous pneumothorax. The associated skin manifestations (fibrofolliculomas) are not always present. This article describes a case of spontaneous pneumothorax secondary to bullous emphysema in an otherwise healthy gentleman caused by a novel mutation in the folliculin (FLCN) gene.

Diffuse Cystic Lung Disease. Part II

The diffuse cystic lung diseases have a broad differential diagnosis. A wide variety of pathophysiological processes spanning the spectrum from airway obstruction to lung remodeling can lead to multifocal cyst development in the lung. Although lymphangioleiomyomatosis and pulmonary Langerhans cell histiocytosis are perhaps more frequently seen in the clinic, disorders such as Birt-Hogg-Dubé syndrome, lymphocytic interstitial pneumonia, follicular bronchiolitis, and light-chain deposition disease are increasingly being recognized. Obtaining an accurate diagnosis can be challenging, and management approaches are highly disease dependent. Unique imaging features, genetic tests, serum studies, and clinical features provide invaluable clues that help clinicians distinguish among the various etiologies, but biopsy is often required for definitive diagnosis. In part II of this review, we present an overview of the diffuse cystic lung diseases caused by lymphoproliferative disorders, genetic mutations, or aberrant lung development and provide an approach to aid in their diagnosis and management.

Partial pleural covering for intractable pneumothorax in patients with Birt-Hogg-Dubé Syndrome

BACKGROUND AND AIMS

Birt-Hogg-Dubé syndrome (BHD) is an inherited disorder associated with a germline mutation of the folliculin (FLCN) gene. Most patients with BHD have multiple pulmonary cysts, and are at high risk of repeated pneumothorax. Although an increasing number of patients are diagnosed with BHD by genetic testing, therapeutic approaches for intractable pneumothorax have not yet been described.

METHODS

We treated three patients who had repeated episodes of pneumothorax. All had multiple pulmonary cysts in the lower lobes, and two had a family history of pneumothorax. Video-assisted thoracic surgery was used to perform wedge resections and partial pleural covering of the cystic lesions. The partial pleural covering technique used sheets of polyglycolic acid felt or regenerative oxidized cellulose mesh. The resected tissues underwent histopathological evaluation, and peripheral blood leukocytes were tested for FLCN mutations.

RESULTS

The operative times were less than 2 h, and there were no complications. The resected cysts had histopathological features characteristic of BHD lung. All patients were found to have FLCN germline mutations; thus their repeated pneumothoraces were a manifestation of BHD. None of the patients developed respiratory problems after undergoing the partial pleural covering procedure, and they have all been well without pneumothorax for 30 months or more.

CONCLUSIONS

Partial pleural covering combined with resection of protruding cysts should be a safe and effective therapeutic approach for BHD patients with intractable pneumothorax. Further investigation is needed to establish a detailed protocol for treatment of pneumothorax that results in minimal functional impairment.

Birt-Hogg-Dubé syndrome detected incidentally by asymptomatic bilateral pneumothorax in health screening: a case of a young Japanese woman

Birt-Hogg-Dubé syndrome (BHD) is an autosomal dominant disease caused by mutations of germline folliculin (FCLN) mapped in the chromosome 17p11.2 region. BHD commonly accompanies renal tumors, fibrofolliculomas, multiple pulmonary cysts, and spontaneous pneumothorax. We report a case of a young Japanese woman in whom asymptomatic bilateral pneumothorax was found incidentally in a health screening, which led to the diagnosis of BHD. She had developed neither renal tumors nor fibrofolliculomas. However, her father, uncle, and aunt also experienced pneumothorax. In Japan, BHD is not yet well known because skin-related symptoms of fibrofolliculomas are sometimes absent unlike in most cases in Europe and the United States. On the basis of this case, we propose that BHD should be considered at the time of pneumothorax examination.

Pulmonary manifestations of Birt-Hogg-Dubé syndrome

Birt-Hogg-Dubé syndrome (BHD) is a rare, autosomal dominant disorder characterized by the development of hair follicle tumors, renal tumors and pulmonary cysts. BHD is caused by heterozygous, predominantly truncating mutations in the folliculin (FLCN) gene located on chromosome 17, which encodes a highly conserved tumor suppressor protein. Although management of renal tumors of low malignant potential is the primary focus of longitudinal care, pulmonary manifestations including cyst formation and spontaneous pneumothorax are among the most common manifestations in BHD. Due to the lack of awareness, there is commonly a delay in the pulmonary diagnosis of BHD and patients are frequently mislabeled as having chronic obstructive lung disease, emphysema or common bullae/blebs. A family history of pneumothorax is present in 35 % of patients with BHD. Certain imaging characteristics of the cysts, including size, basilar and peripheral predominance, perivascular and periseptal localization, and elliptical or lentiform shape can suggest the diagnosis of BHD based on inspection of the chest CT scan alone. Recurrent pneumothoraces are common and early pleurodesis is recommended. A better understanding of role of FLCN in pulmonary cyst formation and long term studies to define the natural history of the pulmonary manifestations of BHD are needed.

Characterization of pulmonary cysts in Birt-Hogg-Dubé syndrome: histopathological and morphometric analysis of 229 pulmonary cysts from 50 unrelated patients

Aims

To characterize the pathological features of pulmonary cysts, and to elucidate the possible mechanism of cyst formation in the lungs of patients with Birt–Hogg–Dubé syndrome (BHDS), a tumour suppressor gene syndrome, using histological and morphometric analyses.

Methods and results

We evaluated 229 lung cysts from 50 patients with BHDS and 117 from 34 patients with primary spontaneous pneumothorax (PSP) for their number, size, location and absence or presence of inflammation. The BHDS cysts abutted on interlobular septa (88.2%) and had intracystic septa (13.6%) or protruding venules (39.5%) without cell proliferation or inflammation. The frequencies of these histological characteristics differed significantly from those seen in the lungs of patients with PSP (P < 0.05). Although the intrapulmonary BHDS cysts were smaller than the subpleural BHDS cysts (P < 0.001), there was no difference in size between them when there was no inflammation. The number of cysts diminished logarithmically and the proportion of cysts with inflammation increased as their individual sizes became greater (P < 0.05).

Conclusions

These results imply that the BHDS cysts are likely to develop in the periacinar region, an anatomically weak site in a primary lobule, where alveoli attach to connective tissue septa. We hypothesize that the BHDS cysts possibly expand in size as the alveolar walls disappear at the alveolar-septal junction, and grow even larger when several cysts fuse.

Distinguishing the histological and radiological features of cystic lung disease in Birt-Hogg-Dubé syndrome from those of tobacco-related spontaneous pneumothorax

AIMS

Birt-Hogg-Dubé syndrome (BHD) is a rare autosomal dominantly inherited genodermatosis that predisposes to cystic lung disease, leading to spontaneous pneumothoraces. This retrospective analysis of five BHD cases (two men, three women) compared lung histology and computed tomography (CT) imaging to a matched cohort of non-BHD patients with spontaneous pneumothoraces (SPN).

METHODS AND RESULTS

Lung was sampled during pleurodesis to resect bullae. Recurrent pneumothoraces was seen in two patients. Fourteen sets of histological slides (seven in each group) and 10 CT scans (five in each group) were reviewed. CT scans in BHD showed multiple cysts with a basal predominance and intraparenchymal/peribronchial distribution. On histological examination, BHD lungs showed punch-out cysts with no inflammation, and lacked subpleural fibroelastotic scars and smoking changes. In contrast, all SPN cases showed respiratory bronchiolitis and subpleural fibroelastotic scars.

CONCLUSIONS

This study emphasizes the importance of smoking history and topography of the lesions in assessing cystic lung disease. Pathologists need to remain alert to the possibility of BHD in the setting of recurrent pneumothoraces in a non-smoker, in particular in a woman, at any age, and should take part in a multidisciplinary approach to the diagnosis of cystic lung disease to obtain clinical and CT scan details.

A de novo FLCN mutation in a patient with spontaneous pneumothorax and renal cancer; a clinical and molecular evaluation

Birt-Hogg-Dubé syndrome (BHD) is an autosomal dominant condition due to germline FLCN (folliculin) mutations, characterized by skin fibrofolliculomas, lung cysts, pneumothorax and renal cancer. We identified a de novo FLCN mutation, c.499C>T (p.Gln167X), in a patient who presented with spontaneous pneumothorax. Subsequently, typical skin features and asymptomatic renal cancer were diagnosed. Probably, de novo FLCN mutations are rare. However, they may be under-diagnosed if BHD is not considered in sporadic patients who present with one or more of the syndromic features. Genetic and immunohistochemical analysis of the renal tumour indicated features compatible with a tumour suppressor role of FLCN. The finding that mutant FLCN was expressed in the tumour might indicate residual functionality of mutant FLCN, a notion which will be explored in future studies.

Diffuse cystic lung diseases

Diffuse cystic lung diseases are uncommon but can present a diagnostic challenge because increasing number of diseases have been associated with this presentation. Cyst in the lung is defined as a round parenchymal lucency with a well-defined thin wall (< 2 mm thickness). Focal or multifocal cystic lesions include blebs, bullae, pneumatoceles, congenital cystic lesions, traumatic lesions, and several infectious processes such as coccidioidomycosis, Pneumocystis jiroveci pneumonia, and hydatid disease. "Diffuse" distribution in the lung implies involvement of all lobes. Diffuse lung involvement with cystic lesions can be seen in pulmonary lymphangioleiomyomatosis, pulmonary Langerhans' cell histiocytosis, lymphoid interstitial pneumonia, Birt-Hogg-Dubé syndrome, amyloidosis, light chain deposition disease, honeycomb lung associated with advanced fibrosis, and several other rare causes including metastatic disease. High-resolution computed tomography of the chest helps define morphologic features of the lung lesions as well as their distribution and associated features such as intrathoracic lymphadenopathy. Correlating the tempo of the disease process and clinical context with chest imaging findings serve as important clues to defining the underlying nature of the cystic lung disease and guide diagnostic evaluation as well as management.

A unique, histopathologic lesion in a subset of patients with spontaneous pneumothorax

CONTEXT

Spontaneous pneumothorax can be idiopathic (primary), or it can occur in association with an underlying predisposing condition (secondary). Spontaneous pneumothorax may be a harbinger of an undiagnosed clinical condition, which may be associated with serious systemic abnormalities, making early recognition and diagnosis important. The pulmonary pathology of some of these disorders has not been fully elucidated.

OBJECTIVE

To review cases of pneumothorax in the hope of identifying pathologic features that might correlate to specific clinical syndromes.

DESIGN

The pathology computer files at 3 hospitals were searched for all cases of spontaneous pneumothorax, primary and secondary, regardless of etiology during a 11-year period. Ninety-two cases were retrieved. Each of the cases was evaluated for reactive eosinophilic pleuritis, elastosis, pleural fibrosis, emphysema, intra-alveolar macrophages, cholesterol clefts, vasculopathy, and intraparenchymal or intrapleural cysts. Clinical information regarding asthma and smoking history, site of the pneumothorax, family history, radiographic findings, predisposing conditions, recurrence, age, and sex were extracted from the medical records.

RESULTS

In 11 patients (12% of all the patients with spontaneous pneumothorax), a distinctive pattern of pleural fibrosis with islands of fibroblastic foci within a myxoid stroma was noted at the pleural-parenchymal interface or leading edge. These lesions correlated with a select subset of patients, consisting predominantly of young men.

CONCLUSIONS

Our review identified a distinct pattern of pneumothorax-associated fibroblastic lesions in a subset of cases of spontaneous pneumothorax. Whether this is related to the pathogenesis of the pneumothorax remains to be elucidated.

Birt-Hogg-Dube syndrome: clinicopathological features of the lung

Birt–Hogg–Dubé syndrome (BHD) is an autosomal dominant inherited disorder characterised by fibrofolliculomas, renal tumours, pulmonary cysts and pneumothorax. The pulmonary cysts and repeated episodes of pneumothorax are the clinical hallmarks for discovering families affected by the syndrome. This disorder is caused by mutations in the gene coding for folliculin (FLCN). FLCN forms a complex with FLCN-interacting protein 1 (FNIP1) and FNIP2 (also known as FNIPL), and the complex cross-talks with signalling molecules such as 5′-AMP-activated protein kinase (AMPK) and the mammalian target of rapamycin (mTOR). Heterozygous Flcn knockout mice and rats with Flcn gene mutations develop renal cysts, adenomas and/or carcinomas. These findings suggest that FLCN functions as a tumour suppressor that inhibits renal carcinogenesis. However, the mechanisms of the formation of pulmonary cysts and pneumothorax associated with heterozygous mutations in FLCN are poorly understood. Resected lung specimens from patients with BHD are often misdiagnosed by pathologists as non-specific blebs or bullae or emphysema, and patients with BHD who have pulmonary cysts and repeated pneumothorax frequently do not receive appropriate medical investigations. This review discusses the clinical and pathological features of lungs of patients with BHD, focusing on the diagnostic pathology and possible mechanisms of cyst formation.

Prostatic atrophy. Clinicopathological significance

Prostatic atrophy is a benign lesion that may mimic adenocarcinoma histologically and on imaging. It is more frequent in the peripheral zone and has gained importance with the increasing use of needle biopsies. Diffuse atrophy occurs secondarily to radiotherapy and/or endocrine therapy. Inflammation and/or chronic local ischemia may cause focal atrophy with an increasing frequency in age. Atrophy may be classified morphologically into diffuse and focal. The latter may be partial, complete or combined. Partial focal atrophy is the most frequent mimicker of adenocarcinoma on needle biopsies. Complete focal atrophy may be subtyped into simple, sclerotic and hyperplastic (or postatrophic hyperplasia). Combined lesions are frequent and partial atrophy may precede complete atrophy. The several morphologic types of focal atrophy may represent a morphologic continuum and the hyperplastic (or postatrophic hyperplasia) subtype seems to be at the extreme end of this continuum. Chronic inflammation associated to focal atrophy (proliferative inflammatory atrophy) has been linked to high-grade prostatic intraepithelial neoplasia and/or carcinoma. This link, however, remains controversial in the literature. The question whether inflammation directly produces tissue damage and atrophy or some other insult induces atrophy directly, with inflammation occurring secondarily, is still unresolved. An intriguing finding that needs further studies is a possible association of extent of atrophy to serum PSA elevation.

Birt-Hogg-Dubé syndrome: diagnosis and management

Birt-Hogg-Dubé syndrome (BHD) is an autosomal dominant condition characterised clinically by skin fibrofolliculomas, pulmonary cysts, spontaneous pneumothorax, and renal cancer. The condition is caused by germline mutations in the FLCN gene, which encodes folliculin; the function of this protein is largely unknown, although FLCN has been linked to the mTOR pathway. The availability of DNA-based diagnosis has allowed insight into the great variation in expression of FLCN, both within and between families. Patients can present with skin signs and also with pneumothorax or renal cancer. Preventive measures are aimed mainly at early diagnosis and treatment of renal cancer. This Review gives an overview of current diagnosis and management of BHD.

A Japanese family with multiple lung cysts and recurrent pneumothorax: a possibility of Birt-Hogg-Dubé syndrome

We herein report a Japanese family lineage, possibly demonstrating Birt-Hogg-Dubé (BHD) syndrome. A 29-year-old nonsmoking woman was admitted to our hospital due to spontaneous pneumothorax. A chest CT showed multiple lung cysts, and breast cancer was simultaneously detected that needed priority surgical treatment. In the family history, the patient's father and half brother also experienced recurrent pneumothorax, and both had similar findings in their chest CT. In a genetic analysis of her half brother, the mutation of the BHD gene was identified. BHD syndrome is a rare autosomal and dominantly inherited disorder, which has three characteristics: multiple lung cysts that may be associated with pneumothorax, skin fibrofolliculomas, and renal neoplasm. For multiple-cystic disease of the lungs with an unknown etiology, or pneumothorax, as seen in a family history, it is necessary to consider the possibility of BHD syndrome.

Folliculin mutations are not associated with severe COPD

Background

Rare loss-of-function folliculin (FLCN) mutations are the genetic cause of Birt-Hogg-Dubé syndrome, a monogenic disorder characterized by spontaneous pneumothorax, fibrofolliculomas, and kidney tumors. Loss-of-function folliculin mutations have also been described in pedigrees with familial spontaneous pneumothorax. Because the majority of patients with folliculin mutations have radiographic evidence of pulmonary cysts, folliculin has been hypothesized to contribute to the development of emphysema.

To determine whether folliculin sequence variants are risk factors for severe COPD, we genotyped seven previously reported Birt-Hogg-Dubé or familial spontaneous pneumothorax associated folliculin mutations in 152 severe COPD probands participating in the Boston Early-Onset COPD Study. We performed bidirectional resequencing of all 14 folliculin exons in a subset of 41 probands and subsequently genotyped four identified variants in an independent sample of345 COPD subjects from the National Emphysema Treatment Trial (cases) and 420 male smokers with normal lung function from the Normative Aging Study (controls).

Results

None of the seven previously reported Birt-Hogg-Dubé or familial spontaneous pneumothorax mutations were observed in the 152 severe, early-onset COPD probands. Exon resequencing identified 31 variants, including two non-synonymous polymorphisms and two common non-coding polymorphisms. No significant association was observed for any of these four variants with presence of COPD or emphysema-related phenotypes.

Conclusion

Genetic variation in folliculin does not appear to be a major risk factor for severe COPD. These data suggest that familial spontaneous pneumothorax and COPD have distinct genetic causes, despite some overlap in radiographic characteristics.

Diagnosis of interstitial lung diseases

Interstitial lung diseases (ILDs), a broad heterogeneous group of parenchymal lung disorders, can be classified into those with known and unknown causes. The definitions and diagnostic criteria for several major forms of ILDs have been revised in recent years. Although well over 100 distinct entities of ILDs are recognized, a limited number of disorders, including idiopathic pulmonary fibrosis, sarcoidosis, and connective tissue disease-related ILDs, account for most ILDs encountered clinically. In evaluating patients with suspected ILD, the clinician should confirm the presence of the disease and then try to determine its underlying cause or recognized clinicopathologic syndrome. Clues from the medical history along with the clinical context and radiologic findings provide the initial basis for prioritizing diagnostic possibilities for a patient with ILD. High-resolution computed tomography of the chest has become an invaluable tool in the diagnostic process. A confident diagnosis can sometimes be made on the basis of high-resolution computed tomography and clinical context. Serologic testing can be helpful in selected cases. Histopathologic findings procured through bronchoscopic or surgical lung biopsy are often needed in deriving a specific diagnosis. An accurate prognosis and optimal treatment strategy for patients with ILDs depend on an accurate diagnosis, one guided by recent advances in our understanding of the causes and pathogenetic mechanisms of ILDs.

Cystic lung disease in Birt-Hogg-Dube syndrome

BACKGROUND

To describe the clinical, radiologic, and histopathologic aspects of cystic lung disease occurring in patients with Birt-Hogg-Dubé (BHD) syndrome, a rare, inheritable, multisystem disorder.

METHODS

We retrospectively reviewed five patients with BHD syndrome evaluated at the Mayo Clinic Rochester from 1998 through 2005.

RESULTS

Mean age (+/- SD) at the time of pulmonary evaluation was 56.4 +/- 4.8 years; four patients were men. Three patients had not received a diagnosis of BHD syndrome at the time of initial CT of the chest. Three patients had a smoking history, and two were nonsmokers. Two patients had a history of recurrent pneumothoraces. Pulmonary function tests available in four patients revealed normal results in one patient and mild airflow obstruction or nonspecific pattern of abnormalities in three patients. CT of the chest revealed cystic lung disease in all five patients; cysts were round to oval in shape, ranged widely in size, and were randomly distributed throughout the lungs, except for a predilection to involve the lung bases more extensively. Three patients with a smoking history had more severe cystic changes compared to nonsmokers and included both patients with recurrent pneumothoraces. Surgical lung biopsy available in one patient revealed emphysema-like changes. Follow-up CT scans available in four patients revealed relative stability over a median interval of 20 months (range, 3 to 66 months).

CONCLUSION

We conclude that cystic lung disease in BHD syndrome varies widely in severity, mimics pulmonary lymphangioleiomyomatosis, and may be worsened by smoking.

Mutations of the Birt Hogg Dube gene in patients with multiple lung cysts and recurrent pneumothorax

RATIONALE

Birt-Hogg-Dubé (BHD) syndrome, a rare inherited autosomal genodermatosis first recognised in 1977, is characterised by fibrofolliculomas of the skin, an increased risk of renal tumours and multiple lung cysts with spontaneous pneumothorax. The BHD gene, a tumour suppressor gene located at chromosome 17p11.2, has recently been shown to be defective. Recent genetic studies revealed that clinical pictures of the disease may be variable and may not always present the full expression of the phenotypes.

OBJECTIVES

We hypothesised that mutations of the BHD gene are responsible for patients who have multiple lung cysts of which the underlying causes have not yet been elucidated.

METHODS

We studied eight patients with lung cysts, without skin and renal disease; seven of these patients have a history of spontaneous pneumothorax and five have a family history of pneumothorax. The BHD gene was examined using PCR, denaturing high-performance liquid chromatography and direct sequencing.

MAIN RESULTS

We found that five of the eight patients had a BHD germline mutation. All mutations were unique and four of them were novel, including three different deletions or insertions detected in exons 6, 12 and 13, respectively and one splice acceptor site mutation in intron 5 resulting in an in-frame deletion of exon 6.

CONCLUSIONS

We found that germline mutations of the BHD gene are involved in some patients with multiple lung cysts and pneumothorax. Pulmonologists should be aware that BHD syndrome can occur as an isolated phenotype with pulmonary involvement.

Lung cysts, spontaneous pneumothorax, and genetic associations in 89 families with Birt-Hogg-Dubé syndrome

RATIONALE

Birt-Hogg-Dubé syndrome (BHDS) is an autosomal, dominantly inherited genodermatosis that predisposes to fibrofolliculomas, kidney neoplasms, lung cysts, and spontaneous pneumothorax.

OBJECTIVES

We evaluated 198 patients from 89 families with BHDS to characterize the risk factors for pneumothorax and genotype-pulmonary associations.

METHODS

Helical computed tomography scans of the chest were used to screen for pulmonary abnormalities. BHD mutation data were used for genotype-pulmonary associations. We examined the relationship of pneumothorax with categorical parameters (sex, smoking history, and lung cysts) and continuous parameters (number of cysts, lung cyst volume, and largest cyst diameter and volume). Logistic regression analyses were used to identify the risk factors associated with pneumothorax.

MEASUREMENTS AND MAIN RESULTS

Twenty-four percent (48/198) of patients with BHDS had a history of pneumothorax. The presence of lung cysts was significantly associated with pneumothorax (p = 0.006). Total lung cyst volume, largest cyst diameter and volume, and every parameter related to the number of lung cysts were significantly associated (p < 0.0001) with pneumothorax. A logistic regression analysis showed that only the total number of cysts in the right parenchymal lower lobe and the total number of cysts located on the pleural surface in the right middle lobe were needed to classify a patient as to whether or not he or she was likely to have a pneumothorax. Exon location of the BHD mutation was associated with the numbers of cysts (p = 0.0002).

CONCLUSIONS

This study indicates that patients with BHDS have a significant association between lung cysts and spontaneous pneumothorax.

Lymphangioleiomyomatosis

BACKGROUND

Lymphangioleiomyomatosis (LAM) is a rare disease that is characterized by proliferation of abnormal smooth muscle-like cells (LAM cells), which leads to the formation of lung cysts, fluid-filled cystic structures in the axial lymphatics, and abdominal tumors. It primarily affects women.

METHODS

The authors present a review of large series, registries, and protocols to highlight the prevalence, pathology, clinical features, diagnosis, and treatment options for patients with LAM.

RESULTS

LAM commonly presents with progressive breathlessness or with recurrent pneumothorax, chylothorax, or sudden abdominal hemorrhage. Computed tomography (CT) scans show numerous thin-walled cysts throughout the lungs, abdominal angiomyolipomas, and lymphangioleiomyomas. Pulmonary function tests show decreased forced expiratory volume in 1 second (FEV1) and diffusion capacity for carbon monoxide (DLCO). Exercise testing shows gas-exchange abnormalities, ventilatory limitation, and hypoxemia that may occur with near-normal lung function.

CONCLUSIONS

No effective treatment currently exists for this progressive disorder. However, recent progress in cancer and smooth muscle cell biology and a better understanding of the factors regulating angiogenesis and lymphangiogenesis may provide a foundation for the development of new therapeutic strategies.