Multifocal micronodular pneumocyte hyperplasia and lymphangioleiomyomatosis in tuberous sclerosis with a TSC2 gene.

A 45-year-old woman with a long-standing diagnosis of tuberous sclerosis (TSC) is presented. She has multifocal micronodular pneumocyte hyperplasia (MMPH) and lymphangioleiomyomatosis (LAM) of the lung, together with the detection of TSC2 gene mutation. During surgery for spontaneous pneumothorax, an open-lung biopsy was performed. Micronodules were well defined, measuring approximately 4 mm in diameter. These MMPHs were histologically composed of papillary proliferation of Type II pneumocytes, with positive immunoreactivity of keratin and surfactant apoprotein. The cystlike spaces, with dilatation and destruction of air spaces, were diffusely formed, and the walls were composed of the spindle cells. Such LAM showed positive immunoreactivity for HMB-45 (a monoclonal antibody specific for human melanoma) and tuberin (the gene product of TSC2). On germline mutation analysis using leukocytes of the present patient, a TSC2 gene mutation was confirmed as a deletion of G (or g) on Exon 9 by polymerase chain reaction-single-strand conformational polymorphism. However, no mutation was detected in her son. With microdissection analysis using paraffin-embedding lung tissues, LOH of the TSC2 gene preliminarily was detected in a LAM lesion but not in MMPH. It is suggested that MMPH, in addition to LAM, could be another pulmonary lesion in TSC patients and that the detection of TSC2 and/or TSC1 gene could essentially be useful for the pathogenesis of MMPH and LAM in TSC patients.     

Pulmonary manifestations in tuberous sclerosis complex

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

Mutational analysis of the tuberous sclerosis gene TSC2 in patients with pulmonary lymphangioleiomyomatosis

Pulmonary lymphangioleiomyomatosis (LAM) is a rare disorder limited almost exclusively to women of reproductive age. LAM affects about 5% of women with tuberous sclerosis complex (TSC). LAM also occurs in women who do not have TSC (sporadic LAM). TSC is a tumour suppressor gene syndrome characterised by seizures, mental retardation, and tumours in the brain, heart, and kidney. Angiomyolipomas, which are benign tumours with smooth muscle, fat, and dysplastic vascular components, are the most common renal tumour in TSC. Renal angiomyolipomas also occur in 63% of sporadic LAM patients. We recently found that 54% of these angiomyolipomas have TSC2 loss of heterozygosity, leading to the hypothesis that sporadic LAM is genetically related to TSC. In this study, we screened DNA from 21 women with sporadic LAM for mutations in all 41 exons of TSC2. Twelve of the patients had known renal angiomyolipomas. No TSC2 mutations were detected. We did find three silent TSC2 polymorphisms. We conclude that patients with sporadic LAM, including those with renal angiomyolipomas, do not have a high frequency of germline mutations in the coding region of TSC2.     

Mutation analysis of the TSC1 and TSC2 genes in Japanese patients with pulmonary lymphangioleiomyomatosis

Pulmonary lymphangioleiomyomatosis (LAM) is a destructive lung disease characterized by a diffuse hamartomatous proliferation of smooth muscle cells (LAM cells) in the lungs. Pulmonary LAM can occur as an isolated form (sporadic LAM) or in association with tuberous sclerosis complex (TSC) (TSC-LAM), a genetic disorder with autosomal dominant inheritance with various expressivity resulting from mutations of either the TSC1 or TSC2 gene. We examined mutations of both TSC genes in 6 Japanese patients with TSC-LAM and 22 patients with sporadic LAM and identified six unique and novel mutations. TSC2 germline mutations were detected in 2 (33.3%) of 6 patients with TSC-LAM and TSC1 germline mutation in 1 (4.5%) of 22 sporadic LAM patients. In accordance with the tumor-suppressor model, loss of heterozygosity (LOH) was detected in LAM cells from 3 of 4 patients with TSC-LAM and from 4 of 8 patients with sporadic LAM. Furthermore, an identical LOH or two identical somatic mutations were demonstrated in LAM cells microdissected from several tissues, suggesting LAM cells can spread from one lesion to another. Our results from Japanese patients with LAM confirmed the current concept of pathogenesis of LAM: TSC-LAM has a germline mutation but sporadic LAM does not; sporadic LAM is a TSC2 disease with two somatic mutations; and a variety of TSC mutations causes LAM. However, our study indicates that a fraction of sporadic LAM can be a TSC1 disease; therefore, both TSC genes should be examined, even for patients with sporadic LAM. Received: August 30, 2001 / Accepted: November 2, 2001     

Mutational analysis of TSC1 and TSC2 genes in Japanese patients with tuberous sclerosis complex

We have surveyed the mutations of TSC1 and TSC2 from 38 (25 sporadic, 11 familial, and 2 unknown) Japanese patients with tuberous sclerosis complex. In 23 of 38 subjects, we detected 18 new mutations in addition to 4 mutations that had been previously reported. We also found 3 new polymorphisms. The mutations were not clustered on a particular exon in either of the genes. Seven TSC1 mutations found in 3 familial and 4 sporadic cases were on the exons (3 missense, 2 nonsense point mutations, a 1-base insertion, and a 2-bp deletion). Fifteen TSC2 mutations were found in 5 familial cases, 10 sporadic cases, and 1 unknown case. The 12 mutations were on the exons (8 missense, 1 nonsense point mutations, a 1-bp insertion, a 5-bp deletion, and a 4-bp replacement) and 3 point mutations were on the exon–intron junctions. Although the patients with TSC2 mutations tend to exhibit relatively severe mental retardation in comparison to those with TSC1 mutations, a genotype–phenotype correlation could not yet be established. The widespread distribution of TSC1/TSC2 mutations hinders the development of a simple diagnostic test, and the identification of individual mutations does not provide the prediction of prognosis. Received: April 5, 1999 / Accepted: June 12, 1999     

Horseshoe kidney and a rare TSC2 variant in two unrelated individuals with tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is an autosomal dominant multisystem disorder characterized by abnormalities involving the skin, brain, kidney (angiomyolipomas, cysts), and heart. Horseshoe kidney has not been considered to be a common renal manifestation of TSC but it has been previously reported in two patients with TSC. We report on two unrelated females with typical manifestations of TSC, horseshoe kidney, and an identical variant c.5138G>A in exon 39 (p.Arg1713His) of TSC2 gene. These cases provide evidence that horseshoe kidney is associated with TSC and add to the evidence for the pathogenicity of this variant. Furthermore, one of the patients also had a diaphragmatic hernia which has been reported twice in the medical literature in individuals with TSC. It is possible that a diaphragmatic hernia is another rare manifestation of TSC and that TSC should be included in the differential diagnosis of infants with a diaphragmatic hernia. Given that both a horseshoe kidney and a diaphragmatic hernia are findings that can be detected prenatally on an ultrasound examination, our findings may have implications for prenatal genetic counseling.     

Missense mutations to the TSC1 gene cause tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterised by the development of hamartomas in a variety of organs and tissues. The disease is caused by mutations in either the TSC1 gene on chromosome 9q34 or the TSC2 gene on chromosome 16p13.3. The TSC1 and TSC2 gene products, TSC1 and TSC2, interact to form a protein complex that inhibits signal transduction to the downstream effectors of the mammalian target of rapamycin (mTOR). Here we investigate the effects of putative TSC1 missense mutations identified in individuals with signs and/or symptoms of TSC on TSC1-TSC2 complex formation and mTOR signalling. We show that specific amino-acid substitutions close to the N-terminal of TSC1 reduce steady-state levels of TSC1, resulting in the activation of mTOR signalling and leading to the symptoms of TSC.     

Mutations and polymorphisms in the tuberous sclerosis complex gene on chromosome 16

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder of benign tumor formation, hamartomata, and hamartias. TSC has been shown to be genetically heterogeneous, with one causative gene mapping to chromosome 9q (denoted TSC1) and at least one other gene on chromosome 16p (denoted TSC2). The TSC2 gene was recently cloned. We have tested 88 TSC probands with the TSC2 cDNA by Southern blotting searching for gross deletions/rearrangements/insertions. We detected two deletions and a rare intragenic polymorphic variant. This is a similar rate of mutation detection (2/88; 2.3%) to that in the orignial report (10/260/;3.8%). The rare polymorphic variant was initially detected in the proband of a chromosome 9-linked multiplex TSC family. The polymorphism segregated with previously tested markers on chromosome 16 independently of the disease gene, verifying that the variation was unrelated to TSC status. We have also begun searching for subtle mutations by SSCA and direct sequencing. After screening three exons, we found two intragenic polymorphic variants. Both polymorphisms are common, making them useful for linkage studies in known affected families. © 1997 Wiley-Liss, Inc.     

Functional characterization of the TSC2 c.3598C>T (p.R1200W) missense mutation that co-segregates with tuberous sclerosis complex in mildly affected kindreds

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterized by a combination of neurological symptoms and hamartomatous growths, and caused by mutations in the TSC1 and TSC2 genes. Overall, TSC2 mutations are associated with a more severe disease phenotype. We identified the c.3598C>T (R1200W) change in the TSC2 gene in seven different families. The clinical phenotypes in the families were mild, characterized by mild skin lesions, remitting epilepsy and a lack of severe mental retardation or major organ involvement. Functional analysis of the TSC2 R1200W variant, and four other TSC2 missense variants associated with a mild TSC phenotype, confirmed that the changes disrupted the TSC1-TSC2 function. Interestingly however, in each case, the TSC1-TSC2 interaction was not affected by the amino acid substitution.     

Multifocal micronodular pneumocyte hyperplasia in a postmenopausal woman with tuberous sclerosis

We report a peculiar case of multifocal micronodular pneumocyte hyperplasia (MMPH) without association of pulmonary lymphangioleiomyomatosis (LAM) in a 56-year-old postmenopausal woman with tuberous sclerosis. This case is surmised to be a forme fruste of tuberous sclerosis. Computed tomography demonstrated multiple micronodules, measuring up to 5 mm in size, present in the bilateral lung fields, but no cystic changes. A proliferation of pleomorphic type-II pneumocytes lining the thickened alveolar septa in an adenomatoid pattern, with an associated increase in alveolar macrophages, was observed without typical nuclear atypia. In fully developed lesions, the ingrowth of more proliferating type-II pneumocytes into the thickened alveolar septa and macrophages filling the alveolar lumens were characteristic findings. Proliferation of immature smooth muscle cells suggesting LAM was not observed. Positive immunohistochemical stains for cytokeratin, epithelial membrane antigen, and surfactant apoproteins A and B, and negative staining for HMB45, alpha-1 smooth muscle actin, desmin, and carcinoembryonic antigen confirmed the characteristics of alveolar lining cells in each MMPH lesion. MMPH associated with tuberous sclerosis in the postmenopausal woman appears to be similar to that described in premenopausal women. The present case is familial rather than sporadic and suggests no relationship between the development of MMPH and the underlying hormonal state. Received: 15 June 1999 / Accepted: 19 October 1999     

Characterisation of TSC1 promoter deletions in tuberous sclerosis complex patients

Tuberous sclerosis complex (TSC), an autosomal dominant disorder, is a multisystem disease with manifestations in the central nervous system, kidneys, skin and/or heart. Most TSC patients carry a pathogenic mutation in either TSC1 or TSC2. All types of mutations, including large rearrangements, nonsense, missense and frameshift mutations, have been identified in both genes, although large rearrangements in TSC1 are scarce. In this study, we describe the identification and characterisation of eight large rearrangements in TSC1 using multiplex ligation-dependent probe amplification (MLPA) in a cohort of 327 patients, in whom no pathogenic mutation was identified after sequence analysis of both TSC1 and TSC2 and MLPA analysis of TSC2. In four families, deletions only affecting the non-coding exon 1 were identified. In one case, loss of TSC1 mRNA expression from the affected allele indicated that exon 1 deletions are inactivating mutations. Although the number of TSC patients with large rearrangements of TSC1 is small, these patients tend to have a somewhat milder phenotype compared with the group of patients with small TSC1 mutations.     

Functional assessment of TSC1 missense variants identified in individuals with tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder caused by mutations in the TSC1 or TSC2 genes. The TSC1 and TSC2 gene products, TSC1 and TSC2, form a complex that inhibits the mammalian target of rapamycin (mTOR) complex 1 (TORC1). Previously, we demonstrated that pathogenic amino acid substitutions in the N-terminal domain of TSC1 (amino acids 50-224) are destabilizing. Here we investigate an additional 21 unclassified TSC1 variants. Our functional assessment identified four substitutions (p.L61R, p.G132D, p.F158S, and p.R204P) between amino acids 50 and 224 that reduced TSC1 stability and prevented the TSC1-TSC2-dependent inhibition of TORC1. In four cases (20%), our functional assessment did not agree with the predictions of the SIFT amino acid substitution analysis software. Our new data confirm our previous finding that the N-terminal region of TSC1 is essential for TSC1 function.     

Pulmonary choriostoma in a case of tuberous sclerosis complex

A 52 years old lady was diagnosed to have Tuberous Sclerosis Complex (TSC) on the basis of 2 major and one minor criterion. She had family history of similar complaints in her sister and two sons. There was involvement of kidney in the form of angiomyolipoma, skin in the form of facial angiofibroma and teeth with a dental pit. She had an unusual lung involvement in the form of multiple small choristomas. Choristoma was diagnosed on transbronchial lung biopsy and was present in the form of disorganised striated muscles. The reported pulmonary manifestations of TCS i.e. lymphangioleiomyomatosis (LAM) and multifocal micronodular pneumocyte hyperplasia (MMPH) are types of hamartomas. Hamartomas and choristomas are both types of disorganized tissue. ‘Choristoma’of lung in TSC however is not reported. Clinopathological correlation of pulmonary hamartoma and choristoma, and treatment in TSC has been discussed.KEY WORDS: Tuberous sclerosis, choristoma, hamartoma     

Exon scanning of the entire TSC2 gene for germline mutations in 40 unrelated patients with tuberous sclerosis

Tuberous sclerosis complex (TSC) is a dominantly inherited multisystem disorder resulting in the development of hamartomatous growths in many organs. Genetic heterogeneity has been demonstrated linking the familial cases to either TSC1 at 9q34.3, or TSC2 at 16p13.3. About two-thirds of the TSC cases are sporadic and appear to represent new mutations. While both genes are thought to account for all familial cases, with each representing approximately 50% of the mutations, the proportion of sporadic cases with mutations in TSC1 and TSC2 is yet to be determined. We have examined the entire coding sequence of the TSC2 gene in 20 familial and 20 sporadic cases and identified a total of twenty-one mutations representing 50% and 55% of familial and sporadic cases respectively. Our rate of mutation detection is significantly higher than other published reports. Twenty out of 21 mutations are novel and include 6 missense, 6 nonsense, 5 frameshifts, 2 splice alterations, a 34 bp deletion resulting in abnormal splicing, and an 18 bp deletion which maintains the reading frame. The mutations are distributed throughout the coding sequence with no specific hot spots. There is no apparent correlation between mutation type and clinical severity of the disease. Our results document that at least 50% of sporadic cases arise from mutations in the TSC2 gene. The location of the mutations described here, particularly the missense events, should be valuable for further functional analysis of this tumor suppressor protein. Hum Mutat 12:408–416, 1998. © 1998 Wiley-Liss, Inc.     

一例 TSC2基因嵌合变异致结节性硬化症患者的遗传学分析

目的:对1个结节性硬化症(tuberous sclerosis complex, TSC)家系进行 TSC1和 TSC2基因变异分析,明确其可能的致病原因。 方法:采集患者及其父母的外周血样,提取基因组DNA,应用靶向二代测序联合Sanger测序进行患者及其父母 TSC1和...     

结节性硬化症家系的基因诊断及产前诊断

目的 对结节性硬化症(tuberous sclerosis complex,TSC)患者进行基因突变检测,并在基因诊断结果明确的基础上应用于产前诊断.方法 应用聚合酶链反应-变性高效液相色谱(polymerase chain reaction-denaturing high-performance liquid chromatography,PCR-DHPLC)、DNA测序技术,对19个家系的21例TSC患者进行TSC1和TSC2基因的突变检测.结果 在19个家系21例患者中发现17种不同的基因突变,其中13种突变未见报道,包括TSCj基因的c.2672delA、c.2672insA和TSC2基因的c.4918insCGCC、c.1143delG、Intron27+1 G＞A、c.1957-1958delAG、Intron5+1 G＞A、c.910insCT、c.2753C＞G、c.4078dupAGCAAGTCCAGCTCCTC、Intron 11-1 G＞A、Intron 14+1 G＞A、c.684 C＞A.对7个家系进行了产前诊断,其中6个家系的胎儿均未发现其家系先证者所具有的突变,胎儿出生后电话随访至1～4岁无TSC的症状出现.而另一家系的胎儿携带有和母亲一样的突变,经遗传咨询后,家属选择了引产.结论 本研究证实的TSC基因突变中,有76.5%(13/17)的突变均未在其他研究中被发现,说明中国人群TSC基因的突变谱可能与其他人群具有较明显的差异;本研究中TSC基因诊断率为89.5%(17/19),提示TSC的发生可能还有其它未知的遗传病因;在有家族史的病例中,TSC1与TSC2有相似的突变比例,而在散发病例中,TSC2的突变更加常见;13种新突变患者的父母均无类似突变,说明TSC致病基因具有较高的自发突变率.     

Molecular genetic and phenotypic analysis reveals differences between TSC1 and TSC2 associated familial and sporadic tuberous sclerosis

Tuberous sclerosis (TSC) is an autosomal dominant disorder characterised by the development of hamartomatous growths in many organs. Sixty to seventy percent of cases are sporadic and appear to represent new mutations. TSC exhibits locus heterogeneity: the TSC2 gene is located at 16p13.3 whilst the TSC1 gene, predicted to encode a novel protein termed hamartin, has recently been cloned from 9q34. With the exception of a contiguous gene deletion syndrome involving TSC2 and PKD1 , TSC1 and TSC2 phenotypes have been considered identical. We have now comprehensively defined the TSC1 mutational spectrum in 171 sequentially ascertained, unrelated TSC patients by single strand conformation polymorphism and heteroduplex analysis of all 21 coding exons, and by assaying a restriction fragment spanning the whole locus. Mutations were identified in 9/24 familial cases, but in only 13/147 sporadic cases. In contrast, a limited screen revealed TSC2 mutations in two of the familial cases and in 45 of the sporadic cases. Thus TSC1 mutations were significantly under-represented among sporadic cases (Fisher's exact p -value = 3.12 x 10(-4)). Both large deletions and missense mutations were common at the TSC2 locus whereas most TSC1 mutations were small truncating lesions. Mental retardation was significantly less frequent among carriers of TSC1 than TSC2 mutations (odds ratio 5.54 for sporadic cases only, 6.78 +/- 1.54 when a single randomly selected patient per multigeneration family was also included). No correlation between mental retardation and the type of mutation was found. We conclude that there is a reduced risk of mental retardation in TSC1 as opposed to TSC2 disease and that consequent ascertainment bias, at least in part, explains the relative paucity of TSC1 mutations in sporadic TSC.      

Pancreatic neuroendocrine tumors in patients with tuberous sclerosis complex

Larson AM, Hedgire SS, Deshpande V, Stemmer-Rachamimov AO, Harisinghani MG, Ferrone CR, Shah U, Thiele EA. Pancreatic neuroendocrine tumors in patients with tuberous sclerosis complex. We explored pancreatic neuroendocrine tumors (PanNETs) associated with tuberous sclerosis complex (TSC) to determine their incidence in the TSC population; define their clinical, radiological, and pathological characteristics; and investigate their association with underlying genotypes. Retrospectively reviewed abdominal imaging of 219 patients with TSC, evaluating the incidence, size, and architecture of pancreatic lesions. Pathology records at Massachusetts General Hospital (MGH) were reviewed for all PanNET diagnoses in patients with TSC. Literature was reviewed for TSC-related PanNET cases. Nine patients with TSC were found to have a pancreatic lesion(s) on abdominal imaging and six patients have been diagnosed with a PanNET by pathology at MGH. Twelve cases of TSC-associated PanNETs have been reported in the literature. Of these 18 PanNET cases, one third were cystic, and the average age at resection was 26 years. Germline TSC2 mutations were found in all patients for whom genetic data were available (n = 3). We did not identify pancreatic angiomyolipomas in this series. Our results suggest that PanNETs are the most common pancreatic lesion in patients with TSC. Focal pancreatic mass lesions, solid or cystic, in patients with TSC should be considered possible PanNETs, and resection of the lesion may be clinically indicated.     

Leiomyomatosis-like lymphangioleiomyomatosis of the colon in a female with tuberous sclerosis.

Smooth muscle lesions of the large bowel, excluding the rectum, are generally rare, and diffuse smooth muscle lesions, termed leiomyomatosis, are even rarer. In this report, we document, for the first time, leiomyomatosis-like lymphangioleiomyomatosis (LAM) of the ascending, transverse, and descending colon in association with bilateral renal angiomyolipoma (AML) in a 30-year-old Chinese female with tuberous sclerosis complex (TSC). She presented with protracted constipation for which a colectomy was performed. Histology disclosed multiple confluent nodular CD34 and CD117 negative smooth muscle proliferation within the large bowel wall, whereas the renal biopsy revealed typical features of AML. Interestingly, the epithelioid smooth muscle cells of both the colonic and renal lesions were HMB45 positive, suggesting that leiomyomatosis-like LAM of the colon, pulmonary LAM and AML are closely related entities. The patient remained free of complications for the last five years after surgery. Leiomyomatosis-like LAM of the large bowel probably represents another manifestation of the tendency of TSC to be associated with proliferative lesions.