Recurrent spontaneous pneumothorax in an NF1 patient with a novel causative variant: broadening genotype-phenotype correlations.

Neurofibromatosis type 1 (NF1) is an autosomal dominant disease with complete penetrance, most commonly known to affect the skin and eyes. Although lung involvement in the form of cysts and bullae occurs in up to 20% of adults, the seemingly intuitive association of NF1 and spontaneous pneumothorax is not widely recognised among clinicians. Here, we report the second case of recurring spontaneous pneumothorax in the context of NF1 with a confirmed molecular diagnosis. In both cases, the NF1 variants featured a premature stop codon in the C-terminal protein domain. Interestingly, our patient had mild skin symptoms, suggesting that spontaneous pneumothorax may not be correlated with cutaneous disease severity. More genotype-phenotype correlation studies are needed for NF1 in general and for its link to spontaneous pneumothorax in particular.

[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.

Clinical and genetic features of 334 Asian patients with Birt-Hogg-Dubé syndrome (BHDS) who presented with pulmonary cysts with or without a history of pneumothorax, with special reference to BHDS-associated pneumothorax.

BACKGROUND: The clinical pulmonary manifestations and genetic features of Birt-Hogg-Dubé syndrome (BHDS) in Asian patients remained unclear. We aimed to clarify the clinical features of BHDS-associated pneumothorax (PTX) and retrospectively investigate potential contributing factors in the largest Asian cohort to date. METHODS: We reviewed the clinical and genetic data collected in 2006-2017, from the BHDS patients who were Asian and presented with pulmonary cysts with or without a history of PTX. RESULTS: Data from 334 (41.3% males; 58.7% females) patients from 297 unrelated families were reviewed. Among them, 314 (94.0%) patients developed PTX. The median age at the first occurrence of PTX was 32 years, which was significantly lower in males (P = 0.003) and patients without notable skin manifestations (P < 0.001). Seventy-six (24.2%) patients experienced their first PTX episode before the age of 25 years. PTX simultaneously occurred in the bilateral lungs of 37 (11.8%) patients. Among 149 patients who had their first PTX episode at least 10 years before BHDS diagnosis, PTX occurred more frequently in males (P = 0.030) and light smokers than in nonsmokers (P = 0.014). The occurrence of PTX peaked in the early 30s and gradually decreased with age but remained high in females (P = 0.001). We identified 70 unique FLCN germline variants, including duplications (46.4%), substitutions (7.1%), insertions/deletions (30.0%), and variants affecting splicing (12.5%). Approximately 80% of Asian patients suspected of having BHDS could be genetically diagnosed by examining FLCN exons 7, 9, 11, 12, and 13. No apparent genotype-phenotype correlation regarding pulmonary manifestations was identified. CONCLUSIONS: Our findings indicate that sex, smoking history, and skin manifestations at BHDS diagnosis significantly influence the clinical features of BHDS-associated PTX. These findings may contribute to the appropriate management and treatment of BHDS-associated PTX.

[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.

Exons 1-3 deletion in FLCN is associated with increased risk of pneumothorax in Chinese patients with Birt-Hogg-Dubé syndrome.

BACKGROUND: The pathogenic variants responsible for Birt-Hogg-Dubé syndrome (BHDS) in folliculin (FLCN) gene mostly consist of point mutations. Although large intragenic deletions/duplications have been reported in several case reports, the relationship between large intragenic deletions/duplications and phenotype in BHDS remains unclear. METHODS: We retrospectively identified and reviewed patients with a large intragenic deletion spanning exons 1-3 and analyzed their phenotypic features to compare with those of point mutation carriers in our hospital from January 1, 2017 to August 31, 2022. RESULTS: Twenty unique point mutations (including 4 novel mutations) were detected in 62 patients from 45 families (90%). Exons 1-3 deletion were identified in 8 patients from 5 families (10%) that resided in the same region, Feidong County of Anhui Province, China. Breakpoint analysis indicated that all the deletion breakpoints were flanked by Alu repeats. The prevalence of exons 1-3 deletion carriers in Feidong County was 8.1-times higher than that for BHDS in Anhui Province, suggesting a clustered phenomenon of exons 1-3 deletion. Significantly increased risk of pneumothorax was observed in those with exons 1-3 deletion compared with point mutations (91% vs. 58%, p value 0.047). The risk of renal cancer may be higher in those with exons 1-3 deletion than for those with point mutations (18% vs. 4%, p > 0.05). CONCLUSIONS: Large intragenic deletion of exons 1-3 in FLCN was identified as a local aggregation phenomenon in Feidong County, China, and was associated with a significantly higher risk of pneumothorax compared to those with point mutations.

[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.

Hemoptysis after COVID-19 and the importance of differential diagnosis: Birt-Hogg-Dubé syndrome.

Birt-Hogg-Dubé syndrome is a genodermatosis of autosomal dominant inheritance characterized by mutations in the folliculin (FLCN) gene. There is an inappropriate inhibition/activation of a protein, the foliculin, which may cause tumor lesions in skin, renal and lung lesions; they could have more risk of developing pneumothorax compared to the normal population. A 38-year-old male patient with bronchial asthma who consulted for hemoptysis three weeks after recovery from COVID-19 infection. A chest tomography was requested, showing an air cyst in the left lower lobe. Physical examination shows evidence of thoracic skin lesions which a skin biopsy was performed on. The results were compatible with fibrofolliculoma. Differential diagnoses were proposed. A genetic disorder associated with skin lesions was suspected. A multi-genetic panel that includes BRCA1, BRCA2, TP53 and FLCN genes was requested, which reported the mutation of the FLCN gene in heterozygosis classified as pathognomonic of Birt-Hogg-Dubé syndrome. Patient is currently under clinical follow-up while genetic counseling was requested for relatives.

El síndrome de Birt-Hogg-Dubé es una genodermatosis de herencia autosómica dominante caracterizada por mutaciones en el gen foliculina (FLCN), donde existe inhibición/activación inapropiada de una proteína, la foliculina, que puede causar lesiones tumorales sistémicas, principalmente a nivel de la piel, renal y lesiones pulmonares, presentando mayor riesgo de desarrollar neumotórax en comparación con la población normal. Comunicamos el caso de un varón de 38 años con asma bronquial que consultó por hemoptisis 3 semanas después de la recuperación de la infección por COVID-19. Se solicitó una tomografía de tórax, que mostró un quiste aéreo en el lóbulo inferior izquierdo. Además, presentaba en el examen físico una lesión cutánea que fue biopsiada, presentando diagnóstico de foliculoma. Se plantearon diagnósticos diferenciales y ante la sospecha de probable desorden genético, un panel genético fue solicitado. Se confirmó síndrome de Birt-Hogg-Dubé ante el hallazgo de la deleción heterocigota que comprende el exón 1 del gen FLCN clasificada como patogénica. Actualmente el paciente se encuentra en seguimiento clínico mientras se solicitó estudio genético para familiares.

The miRNA-24, miRNA-21 expressions and matrix metalloproteinase-7 level in exhaled breath condensate of children with primary spontaneous pneumothorax.

Bullous lung diseases may cause primary spontaneous pneumothorax (PSP) in children. The microRNAs (miRNAs) are non-coding RNAs that participate in regulation of inflammation and cancer. We hypothesized that children with bullous lung disease and PSP may have altered miRNA expressions in their exhaled breath condensates (EBCs). Therefore, a prospective study was performed to evaluate the miRNA-24 and 21 expression, and the matrix metalloproteinase-7 (MMP-7) levels in EBC of children with PSP. Children with PSP were evaluated for age, gender, clinical features and results of surgical treatment. EBC samples (500-1000 ml) were collected to evaluate the miRNA-21, 24 expressions, and MMP-7, and tissue-inhibitor-MMP-1 (TIMP-1) levels. miRNA expressions and MMP levels of patients were compared with healthy controls (control group (CG),n= 12). Subjects (n= 16) with a mean age of 15 years (10-19 years), and a male-to-female ratio of 14:2 were enrolled in this study. The most common presenting symptom was sudden chest pain (n= 14). In 62.5% of the cases an underlying bullous lung disease were detected. During an average of 16.6 months (1-60 months) follow up period, four subjects relapsed. The mean MMP-7 (1.74-1.57 ng ml-1), and TIMP-1 (1.92-1.84 ng ml-1) levels were similar between both groups (p> 0.05). miRNA-24 expression was significantly decreased in the PSP group, when compared to the CG (0.16-1 2-ΔΔCT,p< 0.05). In addition, the miRNA-21 expression was not different between the two groups (p> 0.05). In conclusion, the miRNA-24 levels were significantly decreased in children with PSP. Taken together, children with PSP, especially those with bullous disease, should be closely monitored in the long-term period.

Birt-Hogg-Dubé syndrome: Another mTOR phenomenon.

Birt-Hogg-Dubé syndrome is an uncommon autosomal dominant systemic disorder with cutaneous findings notable for fibrofolliculomas or trichodiscomas on the scalp, face, neck, and trunk. These cutaneous signs are associated with bilateral renal cell carcinoma, benign renal cysts, pulmonary cysts, and spontaneous pneumothorax. Given its autosomal dominant inheritance pattern, the successful diagnosis of Birt-Hogg-Dubé syndrome (BHDS) may elucidate a diagnosis in family members. BHDS results from a mutation in the FLCN gene encoding the folliculin protein, a transcriptional regulator of the mammalian target of rapamycin signaling pathway. Like tuberous sclerosis, BHDS's clinical features may subside with the use of oral rapamycin for mammalian target of rapamycin inhibition, a theoretical concept meriting exploration. Although its prevalence in the general population has been estimated at 2 cases per million, BHDS has been detected in a few patients from the nearby Portuguese-lineage quarter of the city of Newark, a disproportionate prevalence possibly explained by the founder effect.

Epidemiology and clinical features of Birt-Hogg-Dubé syndrome: A nationwide population-based study in South Korea.

BACKGROUND: Birt-Hogg-Dubé (BHD) syndrome is an ultrarare lung disease with unclear prevalence and incidence. Our study aimed to identify the epidemiological and clinical features of BHD syndrome by using nationwide claims data from the Korean Health Insurance Review and Assessment service. METHODS: Patients with BHD syndrome who had the following criteria were included: 1) tested for folliculin gene mutation, and 2) had at least one of the conditions: other specified malformation syndromes, fibrofolliculoma, acrochordon, lung cyst, cancer, and pneumothorax based on International Classification of Disease-10 code. RESULTS: We found 26 patients with BHD syndrome from 2017 to 2019. The prevalence of BHD syndrome was 5.67 per 107 population, with no peak age. Among incidence cases, the median age of diagnosis was 51 years, with slightly more females than males (n = 15, 57.7%). Over half of the patients (n = 14, 53.8%) experienced pneumothorax, and 10 (38.5%) developed malignant neoplasm within the clinical course. CONCLUSIONS: The prevalence of BHD syndrome in Korea is extremely low. However, affected patients manifest several comorbidities, including malignant neoplasm and repetitive pneumothorax.

Frequency of truncating FLCN variants and Birt-Hogg-Dubé-associated phenotypes in a health care system population.

PURPOSE: Penetrance estimates of Birt-Hogg-Dubé syndrome (BHD)-associated cutaneous, pulmonary, and kidney manifestations are based on clinically ascertained families. In a health care system population, we used a genetics-first approach to estimate the prevalence of pathogenic/likely pathogenic (P/LP) truncating variants in FLCN, which cause BHD, and the penetrance of BHD-related phenotypes. METHODS: Exomes from 135,990 patient-participants in Geisinger's MyCode cohort were assessed for P/LP truncating FLCN variants. BHD-related phenotypes were evaluated from electronic health records. Association between P/LP FLCN variants and BHD-related phenotypes was assessed using Firth's logistic regression. RESULTS: P/LP truncating FLCN variants were identified in 35 individuals (1 in 3234 unrelated individuals), 68.6% of whom had BHD-related phenotype(s), including cystic lung disease (65.7%), pneumothoraces (17.1%), cutaneous manifestations (8.6%), and kidney cancer (2.9%). A total of 4 (11.4%) individuals had prior clinical BHD diagnoses. CONCLUSION: In this health care population, the frequency of P/LP truncating FLCN variants is 60 times higher than the previously reported prevalence. Although most variant-positive individuals had BHD-related phenotypes, a minority were previously clinically diagnosed, likely because cutaneous manifestations, pneumothoraces, and kidney cancer were observed at lower frequencies than in clinical cohorts. Improved clinical recognition of cystic lung disease and education concerning its association with FLCN variants could prompt evaluation for BHD.

Birt-Hogg-Dubé syndrome encountered at rare lung disease clinic in Anhui province, China.

BACKGROUND: Diagnosis of rare diseases remains a challenge in China. We describe our experience with Birt-Hogg-Dubé syndrome (BHDS) encountered at a Rare Lung Disease Clinic recently established in China. METHODS: After the first patient with BHDS was recognized in 2017, a Rare Lung Disease Clinic with a multidisciplinary team of specialists was established. We retrospectively analyzed the data of consecutive patients with BHDS encountered from inception to December 2021. RESULTS: There were 1, 1, 15, 12 and 21 cases with BHDS diagnosed from year 2017 to 2021, respectively. All 50 patients (34 women) were of Han race with a mean age of 47.4 years. The common manifestations were pulmonary cysts (98%), pneumothorax (54%) and skin lesions (68%). Renal cancer was detected in two patients and renal angiomyolipoma in four other patients. The main presentations leading to diagnosis were pneumothorax (42%), family screening (36%), and lung cysts identified on radiologic imaging (20%). The average delay in diagnosis was 8.3 years, and 4.7 years in patients with only pulmonary cysts. The most frequent pathogenic variant was c.1285del/dup on exon 11 (23%) among 44 patients confirmed by genetic testing. Renal cancer has not been found on follow-up surveillance thus far. CONCLUSIONS: Increasing number of patients with BHDS are being recognized in China, facilitated by establishment of a Rare Lung Disease Clinic. Pulmonary cysts and pneumothorax were commonly encountered features, but skin lesions appeared to be more prevalent in Chinese subjects than previously reported in other Asian countries.

[Two families with Birt-Hogg-Dubé syndrome:case report and literature review].

Objective: To improve the awareness of Birt-Hogg-Dubé syndrome. Methods: We performed a retrospective analysis with two families of Birt-Hogg-Dubé syndrome (BHD syndrome) diagnosed in Department of Respiratory and Critical Care Medicine, Shenzhen People's Hospital from 2020 to 2021. Clinical manifestations, imaging features, diagnosis and gene detection results were summarized. Relative literatures were reviewed in Wanfang Database and PubMed from 2015 to 2021 by using the search terms of "BHD syndrome" "Birt-Hogg-Dubé" "Birt-Hogg-Dubé syndrome", respectively. Results: The probands of both families were female, aged 37 and 34 years respectively. The onset manifestation was pulmonary bullae combined with pneumothorax. Chest computed tomography (CT) imaging showed multiple pulmonary cysts in both lobes, and no skin lesions or renal tumors were found in either case. History of pneumothorax was present in Family 1 while absent in Family 2. The FLCN gene of the two probands and their relatives showed the same mutation site. Totally 12 Chinese literatures and 394 English literatures were retrieved, among which 96 reported lung involvement only. A total of 10 literatures about Chinese population were screened out from the English literatures, and 115 patients, 31 males and 84 females, were included. The incidence of spontaneous pneumothorax was 66.95% (77/115), while a family history of pneumothorax was 88.31%(68/77). The onset age of spontaneous pneumothorax was between 30 and 44 years. The most common mutation site of FLCN was c.1285dup. Conclusions: BHD syndrome in Asian population may only have lung involvement. Patients with pneumothorax and pulmonary cystic lesions should be inquired of the family history. We speculate that there are many underdiagnosed cases in clinical practice.

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

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

[Alpha-1 antitrypsin deficiency and spontaneous pneumothorax. Just a coincidence?] / Deficiencia de alfa-1 antitripsina y neumotórax espontáneo ¿solo una coincidencia?

Alpha-1 antitrypsin (AAT) deficiency is one of the most common inherited disorders with a higher incidence in patients with chronic obstructive pulmonary disease (COPD). Its prevalence in patients with spontaneous pneumothorax is unknown. The objective was to estimate the prevalence of AAT deficiency in patients with spontaneous pneumothorax. This was a prospective cross-sectional study, in patients with spontaneous pneumothorax, where those with secondary pneumothorax were excluded. Quantification of serum AAT by nephelometry and subsequent rapid genotyping (real time PCR) was performed, in order to detect the most prevalent deficiency alleles (Z and S) in those subjects with serum AAT concentrations = 120 mg/dl. Fifty-eight patients with primary spontaneous pneumothorax were included. The average age was 34 ± 13 years with male predominance (72%) and high prevalence of current and past smoking (60%). Twenty six percent of them (95% CI: 15-39) presented AAT serum concentrations = 120mg/dl. We found 7 deficiency variants (12%; IC 95%: 5-23%). One patient presented a severe Pi•ZZ form (1.7%), 3 were heterozygotes Z (5.2%) and 3 heterozygotes S (5.2%). The prevalence of AAT deficient variants was high in patients with spontaneous pneumothorax.

La deficiencia de alfa-1 antitripsina (AAT) es uno de los trastornos hereditarios más frecuentes y con mayor incidencia en pacientes con enfermedad pulmonar obstructiva crónica (EPOC). Se desconoce su prevalencia en aquellos con neumotórax espontáneo. El objetivo fue estimar la prevalencia de deficiencia de AAT en sujetos con neumotórax espontáneo. El estudio fue prospectivo y de corte transversal en pacientes con neumotórax espontáneo primario. Se excluyeron aquellos con neumotórax secundario. Se realizó cuantificación de AAT en suero por nefelometría y posterior genotipificación rápida (PCR en tiempo real) para detectar los alelos de deficiencia más prevalentes (Z y S) en aquellos con concentraciones séricas = 120 mg/dl. Se incluyeron 58 pacientes con neumotórax espontáneo primario. La edad promedio fue de 34 ± 13 años con predominio de sexo masculino (72%) y alta prevalencia de tabaquismo actual y pasado (60%). Del total, el 26% (IC95%: 15-39) presentó concentraciones de AAT = 120mg/dl. Encontramos 7 formas deficitarias (12%; IC 95%: 5-23%). Un paciente presentó una forma grave Pi•ZZ (1.7%), 3 fueron heterocigotos Z (5.2%) y 3 heterocigotos S (5.2%). La prevalencia de variantes deficitarias de AAT fue alta en este grupo con neumotórax espontáneo.

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.

Deficiencia de alfa-1 antitripsina y neumotórax espontáneo. ¿Solo una coincidencia? / Alpha-1 antitrypsin deficiency and spontaneous pneumothorax. Just a coincidence?

Resumen La deficiencia de alfa-1 antitripsina (AAT) es uno de los trastornos hereditarios más frecuentes y con mayor incidencia en pacientes con enfermedad pulmonar obstructiva crónica (EPOC). Se desconoce su prevalencia en aquellos con neumotórax espontáneo. El objetivo fue estimar la prevalencia de deficiencia de AAT en sujetos con neumotórax espontáneo. El estudio fue prospectivo y de corte transversal en pacientes con neumotórax espontáneo primario. Se excluyeron aquellos con neumotórax secundario. Se realizó cuantificación de AAT en suero por nefelometría y posterior genotipificación rápida (PCR en tiempo real) para detectar los alelos de deficiencia más prevalentes (Z y S) en aquellos con concentraciones séricas ≤ 120 mg/dl. Se incluyeron 58 pacientes con neumotórax espontáneo primario. La edad promedio fue de 34 ± 13 años con predominio de sexo masculino (72%) y alta prevalencia de tabaquismo actual y pasado (60%). Del total, el 26% (IC95%: 15-39) presentó concentraciones de AAT ≤ 120mg/dl. Encontramos 7 formas deficitarias (12%; IC 95%: 5-23%). Un paciente presentó una forma grave Pi*ZZ (1.7%), 3 fueron heterocigotos Z (5.2%) y 3 heterocigotos S (5.2%). La prevalencia de variantes deficitarias de AAT fue alta en este grupo con neumotórax espontáneo.

Abstract Alpha-1 antitrypsin (AAT) deficiency is one of the most common inherited disorders with a higher incidence in patients with chronic obstructive pulmonary disease (COPD). Its prevalence in patients with spontaneous pneumothorax is unknown. The objective was to estimate the prevalence of AAT deficiency in patients with spontaneous pneumothorax. This was a prospective cross-sectional study, in patients with spontaneous pneumothorax, where those with secondary pneumothorax were excluded. Quantification of serum AAT by nephelometry and subsequent rapid genotyping (real time PCR) was performed, in order to detect the most prevalent deficiency alleles (Z and S) in those subjects with serum AAT concentrations ≤ 120 mg/dl. Fifty-eight patients with primary spontaneous pneumothorax were included. The average age was 34 ± 13 years with male predominance (72%) and high prevalence of current and past smoking (60%). Twenty six percent of them (95% CI: 15-39) presented AAT serum concentrations ≤ 120mg/dl. We found 7 deficiency variants (12%; IC 95%: 5-23%). One patient presented a severe Pi*ZZ form (1.7%), 3 were heterozygotes Z (5.2%) and 3 heterozygotes S (5.2%). The prevalence of AAT deficient variants was high in patients with spontaneous pneumothorax.

Lung function in Birt-Hogg-Dubé syndrome: a retrospective analysis of 96 patients.

BACKGROUND: Birt-Hogg-Dubé syndrome (BHD) is a rare autosomal dominant disorder caused by mutations in the FLCN gene coding for folliculin. Its clinical expression includes cutaneous fibrofolliculomas, renal tumors, multiple pulmonary cysts, and recurrent spontaneous pneumothoraces. Data on lung function in BHD are scarce and it is not known whether lung function declines over time. We retrospectively assessed lung function at baseline and during follow-up in 96 patients with BHD. RESULTS: Ninety-five percent of BHD patients had multiple pulmonary cysts on computed tomography and 59% had experienced at least one pneumothorax. Mean values of forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), FEV1/FVC ratio, and total lung capacity were normal at baseline. Mean (standard deviation) residual volume (RV) was moderately increased to 116 (36) %pred at baseline, and RV was elevated > 120%pred in 41% of cases. Mean (standard deviation) carbon monoxide transfer factor (DLco) was moderately decreased to 85 (18) %pred at baseline, and DLco was decreased < 80%pred in 33% of cases. When adjusted for age, gender, smoking and history of pleurodesis, lung function parameters did not significantly decline over a follow-up period of 6 years. CONCLUSIONS: Cystic lung disease in BHD does not affect respiratory function at baseline except for slightly increased RV and reduced DLco. No significant deterioration of lung function occurs in BHD over a follow-up period of 6 years.

Birt-Hogg-Dubé syndrome. / Birt-Hogg-Dubé-syndrom.

Birt-Hogg-Dubé syndrome (BHD) is an autosomal dominant genetic disorder characterised by pulmonary cysts, fibrofolliculomas and renal tumours. The pulmonary cysts may lead to pneumothorax, and in cases of primary, spontaneous pneumothorax the syndrome should be excluded. The renal tumours are frequently malignant, but slow-growing. Screening and family assessment enable discovery of renal cancer at an early stage. The syndrome is underdiagnosed and little known.