[Diffuse cystic lung disease]. / Cystische Lungenerkrankungen.

INTRODUCTION: Diffuse cystic lung disease (DCLD) represents a heterogeneous group of conditions, typically characterized by the presence of multiple thin-walled, predominantly round parenchymal lucencies. The increased accessibility of computed tomography (CT) underscores the growing relevance of a relatively rare group of diseases as more clinicians are confronted with the presence of multiple lung cysts on the chest CT scan. Although the etiology of these conditions is very diverse, the focus of the differential diagnosis revolves around four primary causative factors - Lymphangioleiomyomatosis (LAM), Pulmonary Langerhanscell histiocytosis (PLCH), Birt-Hogg-Dubé (BHD) and lymphoid interstitial pneumonia (LIP). Achieving an accurate diagnosis poses a challenge and typically necessitates lung biopsies; however, it is crucial for ensuring proper management.

[Genetic diffuse cystic lung disease in adults]. / Maladies kystiques pulmonaires de l'adulte d'origine génétique.

Multiple cystic lung diseases comprise a wide range of various diseases, some of them of genetic origin. Lymphangioleiomyomatosis (LAM) is a disease occurring almost exclusively in women, sporadically or in association with tuberous sclerosis complex (TSC). Patients with LAM present with lymphatic complications, renal angiomyolipomas and cystic lung disease responsible for spontaneous pneumothoraces and progressive respiratory insufficiency. TSC and LAM have been ascribed to mutations in TSC1 or TSC2 genes. Patients with TSC are variably affected by cutaneous, cognitive and neuropsychiatric manifestations, epilepsy, cerebral and renal tumors, usually of benign nature. Birt-Hogg-Dubé syndrome is caused by mutations in FLCN encoding folliculin. This syndrome includes lung cysts of basal predominance, cutaneous fibrofolliculomas and various renal tumors. The main complications are spontaneous pneumothoraces and renal tumors requiring systematic screening. The mammalian target of rapamycin (mTOR) pathway is involved in the pathophysiology of TSC, sporadic LAM and Birt-Hogg-Dubé syndrome. MTOR inhibitors are used in LAM and in TSC while Birt-Hogg-Dubé syndrome does not progress towards chronic respiratory failure. Future challenges in these often under-recognized diseases include the need to reduce the delay to diagnosis, and to develop potentially curative treatments. In France, physicians can seek help from the network of reference centers for the diagnosis and management of rare pulmonary diseases.

Recommendations on scuba diving in Birt-Hogg-Dubé syndrome.

INTRODUCTION: Although very uncommon, severe injury and death can occur during scuba diving. One of the main causes of scuba diving fatalities is pulmonary barotrauma due to significant changes in ambient pressure. Pathology of the lung parenchyma, such as cystic lesions, might increase the risk of pulmonary barotrauma. AREAS COVERED: Birt-Hogg-Dubé syndrome (BHD), caused by pathogenic variants in the FLCN gene, is characterized by skin fibrofolliculomas, an increased risk of renal cell carcinoma, multiple lung cysts and spontaneous pneumothorax. Given the pulmonary involvement, in some countries patients with BHD are generally recommended to avoid scuba diving, although evidence-based guidelines are lacking. We aim to provide recommendations on scuba diving for patients with BHD, based on a survey of literature on pulmonary cysts and pulmonary barotrauma in scuba diving. EXPERT OPINION: In our opinion, although the absolute risks are likely to be low, caution is warranted. Given the relative paucity of literature and the potential fatal outcome, patients with BHD with a strong desire for scuba diving should be informed of the potential risks in a personal assessment. If available a diving physician should be consulted, and a low radiation dose chest computed tomography (CT)-scan to assess pulmonary lesions could be considered.

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

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

Pulmonary interstitial glycogenosis in Birt-Hogg-Dubé syndrome-associated lung cysts: A new insight into the pathogenesis?

Multiple lung cysts are one of the major features of Birt-Hogg-Dubé syndrome (BHD), but little is known about their nature and pathogenesis. We report a case of a woman diagnosed with BHD lung cysts who exhibited pulmonary interstitial glycogenosis (PIG), a mesenchymal abnormality hitherto undescribed in this disease, in specimens resected at 14 and 29 years of age. Histopathologically, oval to spindle clear cells were seen in the subepithelial interstitial tissue of septal structures and the walls of the cysts. They had abundant periodic acid-Schiff-positive cytoplasmic glycogen. Immunohistochemically, these cells were positive for a few markers of mesenchymal stem cell-like lineage, including vimentin, CD44, and CD10, and negative for markers of epithelial or specific mesenchymal differentiation; these results were consistent with the reported immunophenotype of PIG cells. These PIG cells were more abundant in her specimen at age 14 years than in the second specimen from adulthood. The present case suggests that BHD lung cysts belong to a group of pulmonary developmental disorders characterized by combined PIG and alveolar simplification/cystic change. Disorders with PIG may persist until adulthood and may be of clinical and pathological significance.

A splicing mutation of the FLCN gene is associated with Birt-Hogg-Dubé syndrome characterized by familial and recurrent spontaneous pneumothorax: A case report.

RATIONALE: Birt-Hogg-Dubé (BHD) syndrome is a rare autosomal recessive genetic disorder caused mainly by mutations in the tumor suppressor FLCN gene. Tumors caused by FLCN mutations are frequently benign and develop in skin, lungs, kidney, and other organs, leading to a variety of phenotypes that make early diagnoses of BHD challenging. PATIENT CONCERNS: A 51-year-old female was admitted to Shanghai Seventh People Hospital due to chest congestion and dyspnea that had persisted for 3 years and aggravated for 1 month. She had been diagnosed with pneumothorax prior to this submission, but the etiology was unknown. DIAGNOSES: Chest computed tomography (CT) revealed multiple pulmonary cysts and pneumothorax, and her family members shared similar manifestation. Whole-exome sequencing analysis indicated a heterozygous FLCN splicing mutation (c.1432 + 1G > A; rs755959303), which was a pathogenic variant indicated in ClinVar. Based on FLCN mutation and the family history of pulmonary cysts and pneumothorax, BHD syndrome was finally diagnosed, which had been delayed for 3 years since her first pneumothorax. INTERVENTIONS: Pulmonary bullectomy and pleurodesis were finally conducted due to the poor effects of thoracic close drainage. OUTCOMES: Her pneumothorax was resolved, and no recurrence was found in 2 years. LESSONS: Our study highlights the importance of genetic analysis in diagnosis and clinical management of BHD syndrome.

Clinical phenotype and genetic function analysis of a rare family with hereditary leiomyomatosis and renal cell carcinoma complicated with Birt-Hogg-Dubé syndrome.

To date, over 200 families with hereditary leiomyomatosis and renal cell carcinoma (HLRCC) and over 600 families with Birt-Hogg-Dubé (BHD) syndrome have been reported, with low incidence. Here, we describe a patient with suspected rare HLRCC complicated by BHD syndrome. The proband (II1) had characteristic cutaneous leiomyoma-like protrusions on the neck and back, a left renal mass and multiple right renal, liver and bilateral lung cysts. Three family members (I1, II2, II3) had a history of renal cancer and several of the aforementioned clinical features. Two family members (II1, II3) diagnosed with fumarate hydratase (FH)-deficient papillary RCC via pathological biopsy carried two heterozygous variants: FH (NM_000143.3) missense mutation c.1189G>A (p.Gly397Arg) and FLCN (NM_144997.5) frameshift mutation c.1579_1580insA (p.Arg527Glnfs*75). No family member carrying a single variant had renal tumours. In HEK293T cells transfected with mutant vectors, mRNA and protein expression after FLCN p.Arg527Glnfs*75 and FH p.Gly397Arg mutations were significantly lower than those in wild-type (WT) cells. Cell immunofluorescence showed altered protein localisation and reduced protein expression after FLCN p.Arg527Glnfs*75 mutation. The FH WT was uniformly distributed in the cytoplasm, whereas FH protein expression was reduced after the p.Gly397Arg mutation and scattered sporadically with altered cell localisation. Patients with two variants may have a significantly increased penetrance of RCC.

PRDM10 RCC: A Birt-Hogg-Dubé-like Syndrome Associated With Lipoma and Highly Penetrant, Aggressive Renal Tumors Morphologically Resembling Type 2 Papillary Renal Cell Carcinoma.

OBJECTIVE: To characterize the clinical manifestations and genetic basis of a familial cancer syndrome in patients with lipomas and Birt-Hogg-Dubé-like clinical manifestations including fibrofolliculomas and trichodiscomas and kidney cancer. METHODS: Genomic analysis of blood and renal tumor DNA was performed. Inheritance pattern, phenotypic manifestations, and clinical and surgical management were documented. Cutaneous, subcutaneous, and renal tumor pathologic features were characterized. RESULTS: Affected individuals were found to be at risk for a highly penetrant and lethal form of bilateral, multifocal papillary renal cell carcinoma. Whole genome sequencing identified a germline pathogenic variant in PRDM10 (c.2029 T>C, p.Cys677Arg), which cosegregated with disease. PRDM10 loss of heterozygosity was identified in kidney tumors. PRDM10 was predicted to abrogate expression of FLCN, a transcriptional target of PRDM10, which was confirmed by tumor expression of GPNMB, a TFE3/TFEB target and downstream biomarker of FLCN loss. In addition, a sporadic papillary RCC from the TCGA cohort was identified with a somatic PRDM10 mutation. CONCLUSION: We identified a germline PRDM10 pathogenic variant in association with a highly penetrant, aggressive form of familial papillary RCC, lipomas, and fibrofolliculomas/trichodiscomas. PRDM10 loss of heterozygosity and elevated GPNMB expression in renal tumors indicate that PRDM10 alteration leads to reduced FLCN expression, driving TFE3-induced tumor formation. These findings suggest that individuals with Birt-Hogg-Dubé-like manifestations and subcutaneous lipomas, but without a germline pathogenic FLCN variant, should be screened for germline PRDM10 variants. Importantly, kidney tumors identified in patients with a pathogenic PRDM10 variant should be managed with surgical resection instead of active surveillance.

[Pneumothorax as an early indication for a genetic disorder]. / Pneumothorax als vroege aanwijzing voor een erfelijke aandoening.

BACKGROUND: Several hereditary disorders, with highly variable and sometimes difficult to recognize manifestations, can present with a spontaneous pneumothorax. Options to perform DNA-testing have changed rapidly, as a result of which physicians of diverse disciplines are coming into contact with hereditary disorders. CASE DESCRIPTION: Two patients with a history of multiple spontaneous pneumothoraxes were seen at the outpatient clinic of the department of Clinical Genetics. Based on family history and physical examination, a suspicion of an underlying hereditary disorder arose. Birt-Hogg-Dubé syndrome and vascular Ehlers-Danlos syndrome were diagnosed through DNA-testing. Based on this, additional screening advices were given and DNA-testing became possible in the family. CONCLUSION: A spontaneous pneumothorax may be a manifestation of an underlying hereditary disorder. With attention to clinical symptoms and family history, physicians can contribute to timely diagnosis. In many cases this results in significant health benefits for both the patient and affected family members, such as screening for kidney cancer in the case of Birt-Hogg-Dubé syndrome.

[Not a pneumothorax again! Birt-Hogg-Dubé syndrome: a case report]. / "Nicht schon wieder ein Pneumothorax" ­ Fallbericht Birt-Hogg-Dubé-Syndrom.

Case discussion of a 40-year-old male patient with a history of recurrent pneumothoraces due to Birt-Hogg-Dubé syndrome. In addition to conservative treatment of a pneumothorax on the left side, a subtotal parietal pleurectomy on the right side was performed after recurrence of a pneumothorax 6 years later. CT of the thorax showed high-grade structural remodelling of the lung parenchyma with cystic lung lesions on both sides with a diameter of up to 7.5 cm. After exclusion of alpha-1 antitrypsin deficiency, underlying immunological disease, unremarkable family and occupational history, Birt-Hogg-Dubé syndrome was suspected based on the morphological distribution pattern of the cystic lung lesions. Genetic examination helped detect a heterozygous pathogenic variant in the FLCN gene, namely c.1294_1298del;p.(Ser432Argfs*22). Birt-Hogg-Dubé syndrome is a rare genetic disorder clinically characterized by pulmonary cysts, fibrofolliculomas of the skin and occurrence of clustered renal tumors. In particular, the increased risk of renal malignancies and the risk of spontaneous pneumothoraces underlines the importance of early diagnosis and screening of affected patients and their families.

Comparative analyses define differences between BHD-associated renal tumour and sporadic chromophobe renal cell carcinoma.

BACKGROUND: Birt-Hogg-Dubé (BHD) syndrome, caused by germline alteration of folliculin (FLCN) gene, develops hybrid oncocytic/chromophobe tumour (HOCT) and chromophobe renal cell carcinoma (ChRCC), whereas sporadic ChRCC does not harbor FLCN alteration. To date, molecular characteristics of these similar histological types of tumours have been incompletely elucidated. METHODS: To elucidate renal tumourigenesis of BHD-associated renal tumours and sporadic renal tumours, we conducted whole genome sequencing (WGS) and RNA-sequencing (RNA-seq) of sixteen BHD-associated renal tumours from nine unrelated BHD patients, twenty-one sporadic ChRCCs and seven sporadic oncocytomas. We then compared somatic mutation profiles with FLCN variants and RNA expression profiles between BHD-associated renal tumours and sporadic renal tumours. FINDINGS: RNA-seq analysis revealed that BHD-associated renal tumours and sporadic renal tumours have totally different expression profiles. Sporadic ChRCCs were clustered into two distinct clusters characterized by L1CAM and FOXI1 expressions, molecular markers for renal tubule subclasses. Increased mitochondrial DNA (mtDNA) copy number with fewer variants was observed in BHD-associated renal tumours compared to sporadic ChRCCs. Cell-of-origin analysis using WGS data demonstrated that BHD-associated renal tumours and sporadic ChRCCs may arise from different cells of origin and second hit FLCN alterations may occur in early third decade of life in BHD patients. INTERPRETATION: These data further our understanding of renal tumourigenesis of these two different types of renal tumours with similar histology. FUNDING: This study was supported by JSPS KAKENHI Grants, RIKEN internal grant, and the Intramural Research Program of the National Institutes of Health (NIH), National Cancer Institute (NCI), Center for Cancer Research.

[Pneumothorax with Birt-Hogg-Dubé Syndrome Diagnosed by Family History:Report of a Case].

Birt-Hogg-Dubé (BHD) syndrome is a rare autosomal and predominantly inherited disorder. A 43 year-old woman was admitted to our hospital for right spontaneous pneumothorax and the thoracoscopic pulumonary wedge resection was performed. A chest computed tomography (CT) scan before surgery showed multiple bilatetal thin walled pulmonary cysts predominant to the lower mediastinum side of the lung field. Since her brother had history of pneumothorax with BHD syndrome. Diagnosed by deoxyribonucleic acid (DNA) sequence analysis of his BHD gene, she was diagnosed as BHD syndrome.

Lymphangioleiomyomatosis and Other Cystic Lung Diseases.

Cysts and cavities in the lung are commonly encountered on chest imaging. It is necessary to distinguish thin-walled lung cysts (≤2 mm) from cavities and characterize their distribution as focal or multifocal versus diffuse. Focal cavitary lesions are often caused by inflammatory, infectious, or neoplastic processes in contrast to diffuse cystic lung diseases. An algorithmic approach to diffuse cystic lung disease can help narrow the differential diagnosis, and additional testing such as skin biopsy, serum biomarkers, and genetic testing can be confirmatory. An accurate diagnosis is essential for the management and disease surveillance of extrapulmonary complications.

Germline- and Somatic-Inactivating FLCN Variants in Parathyroid Cancer and Atypical Parathyroid Tumors.

CONTEXT: Parathyroid cancer (PC) is a rare endocrine neoplasm with high mortality. While surgery is the treatment for patients with the disease, recurrence rates are high, and patients usually succumb to severe hypercalcemia. There is no effective systemic therapy for the disease. OBJECTIVE: To investigate for novel genes causing parathyroid cancer. METHODS: We analyzed the germline DNA of 17 patients with "sporadic" PC and 3 with atypical parathyroid tumors (APTs) who did not have germline CDC73 or MEN1 pathogenic variants. Sequencing of available tumor tissue from 14 patients with PC and 2 with APT was also performed (including 2 patients with no available germline DNA). In addition, sporadic parathyroid adenomas from 74 patients were analyzed for FLCN variants. RESULTS: We identified germline FLCN variants in 3 unrelated patients with PC. The 2 frameshift variants have been described in patients with Birt-Hogg-Dubé (BHD) syndrome, while the pathogenicity of the missense variant c.124G > C (p.G42R) has not been definitively established. Functional analysis of the missense variant showed a potential effect on posttranslational modification. All 3 patients with germline FLCN variants were noted to have renal cysts and 2 had lung cysts, features associated with BHD syndrome. Somatic FLCN variants were identified in tumors from 2 (1 APT) of 16 patients with PC/APT and in none of the 74 sporadic parathyroid adenomas. No second hits in FLCN were noted on sequencing; however, loss of heterozygosity at the locus was demonstrated in 2 of 3 patients with the identified germline FLCN variant. CONCLUSION: The finding of FLCN variants associated with PC may provide the foundation for the development of therapy for this malignancy.

Phaeochromocytoma in a patient with a Birt-Hogg-Dubé syndrome phenotype.

A case of phaeochromocytoma in a female patient in her 50s with phenotypical expressions for the rare Birt-Hogg-Dubé (BHD) syndrome is presented. Whether this is an incidental finding or that there is a composite relationship between these two entities remains to be fully described. Less than 10 cases reporting likely association of BHD syndrome with adrenal tumours have been reported in the literature to date.

FLCN-Driven Functional Adrenal Cortical Carcinoma with High Mitotic Tumor Grade: Extending the Endocrine Manifestations of Birt-Hogg-Dubé Syndrome.

Adrenal cortical carcinoma is an aggressive and rare malignancy of steroidogenic cells of the adrenal gland. Most adult adrenal cortical carcinomas are sporadic, but a small fraction may be associated with inherited tumor syndromes, such as Li-Fraumeni, multiple endocrine neoplasia 1, Lynch syndrome, and Beckwith-Wiedemann syndrome, as well as isolated case reports of non-syndromic manifestations occurring in the context of other pathogenic germline variants. Birt-Hogg-Dubé (BHD) is a rare autosomal dominant syndrome caused by germline pathogenic variants in the FLCN gene. BHD syndrome causes a constellation of symptoms, including cutaneous manifestations, pulmonary cysts and pneumothorax, and risk of renal tumors. With the exception of a single case of adrenal cortical carcinoma, very few reports on the occurrence of adrenal cortical neoplasia in patients with BHD syndrome have been described. However, information on variant allele fraction in the tumor was not available in the index case, which precludes any mechanism supporting loss of heterozygosity. Here we present a case of an adult-onset adrenal cortical carcinoma in a 50-year-old female, found to harbor a germline likely pathogenic variant in the FLCN gene, denoted as c.694C > T (p.Gln232Ter). Genetic testing on the tumor revealed the same FLCN variant at an allele fraction of 83%, suggesting a contributory role to the pathogenesis of the adrenal cortical carcinoma. This case further supports the expansion of the clinical presentation and tumor spectrum of BHD syndrome and the need to consider germline FLCN testing in the clinical genetic workup of patients with adrenal cortical carcinomas.

A diagnosis of Birt-Hogg-Dubé syndrome in individuals with Smith-Magenis syndrome: Recommendation for cancer screening.

We report a series of four unrelated adults with Smith-Magenis syndrome (SMS) and concomitant features of Birt-Hogg-Dubé (BHD) syndrome based upon haploinsufficiency for FLCN and characteristic renal cell carcinomas and/or evidence of cutaneous fibrofolliculomas. Three of the cases constitute the first known association of histopathologically verified characteristic BHD-associated renal tumors in adults with SMS; the fourth was identified to have histologically confirmed skin fibrofolliculomas. Molecular analysis documented second-hit FLCN mutations in two of the three cases with confirmed BHD renal pathology. These cases suggest the need to expand management recommendations for SMS to include kidney cancer surveillance starting at 20 years of age, as per the screening recommendations for BHD syndrome.