Marfan's syndrome

Role of genetic analysis in the management of patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a recognized cause of sudden cardiac death, which may be prevented by timely detection and intervention. Clinical diagnosis of ARVC is fraught with difficulties in both index cases and relatives owing to the nonspecific nature of associated features, diverse phenotypic manifestations, and a lack of conspicuous abnormalities in the early, "concealed" phase. During the past 7 years, researchers have isolated causative mutations in several components of the desmosome, shedding light on the molecular mechanisms underlying the disease and offering the promise of genetic testing as a diagnostic tool. Sequence analysis is likely to be the mainstay of genotyping in ARVC because of marked allelic heterogeneity, frequent "private" mutations, and digenicity in a minority, highlighting the importance of comprehensive genetic screening. The main technical obstacle to implementation of genotyping in clinical practice will be the prohibitive costs of performing sequence analysis of a genomic region exceeding 40 kb. Nevertheless, the success rate of genotyping in ARVC is of the order of 40%, and key clinical applications include confirmatory testing of index cases to facilitate interpretation of borderline investigations and cascade screening of families. The latter is particularly attractive in ARVC, because age-related penetrance otherwise demands lifelong clinical reassessment of extended families. A role for genetic analysis in prognostication is more tenuous at present, but increasing identification of individuals with early and familial disease underscores the need for a definitive risk stratification algorithm in this population.

May TGFBR1 act also as low penetrance allele in Marfan syndrome?

Marfan syndrome, a human disease involving cardiovascular and skeletal apparatuses and ocular and central nervous systems, is associated to mutations in FBN1 gene; heterozygous mutations in TGFBR2 and TGFBR1 genes were found associated to MFS type 2, characterized by the presence of skeletal and cardiovascular major criteria and absence of eye major criterion. We screened the TGFBR1 gene in 46 Marfan patients in whom mutations in FBN1 and TGFBR2 genes were excluded and the analysis of Ex1 was extended to additional 114 Marfan patients and 237 controls. We detected two potentially pathological sequence variants: the TGFBR1 6Ala allele whose frequency was higher in the group of Marfan patients (0.13) than in the controls (0.08) (p=0.013; OR=1.69) and an insertion of 20 nucleotides in the 5'UTR that turned out to be a familial silent rare polymorphism. We hypothesize that TGFBR1 sequence variants may act not only as major, but also as low penetrance alleles of the clinical phenotype in Marfan syndrome.

Catheter ablation for atrial fibrillation in patients with the Marfan and Marfan-like syndromes

Patients with the Marfan syndrome may pose a difficult challenge for catheter-based interventions due to frequent coexisting valve disease, potential delay in vascular healing and repair, and intra-atrial scar from prior cardiac surgery. We report a case series of four patients with Marfan or Marfan-like syndromes who underwent ablation for drug-refractory atrial fibrillation. Ultimately three of four patients remained in sinus rhythm, however most patients required multiple ablative attempts and long-term atrial flutter was common. Nonetheless, peri-procedural complications were minimal despite the connective tissue disorder and prosthetic valves in three of four patients. In conclusion, catheter ablation of AF in patients with Marfan syndrome is a viable option in those individuals refractory to conventional therapy.

Aortic dilatation and dissection in Turner syndrome

BACKGROUND

The risk for aortic dissection is increased among relatively young women with Turner syndrome (TS). It is unknown whether aortic dilatation precedes acute aortic dissection in TS and, if so, what specific diameter predicts impending deterioration.

METHODS AND RESULTS

Study subjects included 166 adult volunteers with TS (average age, 36.2 years) who were not selected for cardiovascular disease and 26 healthy female control subjects. Ascending and descending aortic diameters were measured by magnetic resonance imaging at the right pulmonary artery. TS women were on average 20 cm shorter, yet average aortic diameters were identical in the 2 groups. Ascending aortic diameters normalized to body surface area (aortic size index) were significantly greater in TS, and approximately 32% of TS women had values greater than the 95th percentile of 2.0 cm/m2. Ascending diameter/descending diameter ratios also were significantly greater in the TS group. During approximately 3 years of follow-up, aortic dissections occurred in 3 women with TS, for an annualized rate of 618 cases/100,000 woman-years. These 3 subjects had ascending aortic diameters of 3.7 to 4.8 cm and aortic size indices > 2.5 cm/m2.

CONCLUSIONS

The risk for aortic dissection is greatly increased in young women with TS. Because of their small stature, ascending aortic diameters of < 5 cm may represent significant dilatation; thus, the use of aortic size index is preferred. Individuals with a dilated ascending aorta defined as aortic size index > 2.0 cm/m2 require close cardiovascular surveillance. Those with aortic size index > or = 2.5 cm/m2 are at highest risk for aortic dissection.

Monogenic vessel diseases related to ischemic stroke: a clinical approach

The identification of stroke cases caused by monogenic disorders is important both for therapeutic decisions and genetic counselling, although they represent less than 1% of all stroke patients. The purpose of this review is to summarize genetic, pathological, and clinical features of single-gene disorders related to ischemic stroke. The following monogenic disorders are considered: cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy, cerebral autosomal-recessive arteriosclerosis with subcortical infarcts and leukoencephalopathy, hereditary endotheliopathy with retinopathy, nephropathy, and stroke, Fabry disease, pseudoxanthoma elasticum, Neurofibromatosis type 1, familial MoyaMoya disease, Ehlers-Danlos syndrome type IV, Marfan syndrome. For each monogenic disorder, mode of inheritance, pathophysiological aspects, clinical phenotype, and diagnostic tools are carefully described. Furthermore, the classification of monogenetic disorders is presented according to stroke mechanisms, which include small vessel diseases, large artery diseases, and arterial dissections. This review could be useful to identify specific diagnostic pathways for patients with a suspicion of monogenic disease.

Rationale and design of a randomized clinical trial of beta-blocker therapy (atenolol) versus angiotensin II receptor blocker therapy (losartan) in individuals with Marfan syndrome

BACKGROUND

Cardiovascular disease, including aortic root dilation, dissection, and rupture, is the leading cause of mortality in patients with Marfan syndrome (MFS). The maximal aortic root diameter at the sinuses of Valsalva is considered the best predictor of adverse cardiovascular outcome. Although advances in therapy have improved life expectancy, affected individuals continue to suffer cardiovascular morbidity and mortality. Recent studies in an FBN1-targeted mouse model of MFS with aortic disease similar to that seen in humans showed that treatment with losartan normalized aortic root growth and aortic wall architecture.

METHODS

The Pediatric Heart Network designed a randomized clinical trial to compare aortic root growth and other short-term cardiovascular outcomes in subjects with MFS receiving atenolol or losartan. Individuals 6 months to 25 years of age with a body surface area-adjusted aortic root z score >3.0 will be eligible for inclusion. The primary aim is to compare the effect of atenolol therapy with that of losartan therapy on the rate of aortic root growth over 3 years. Secondary end points include progression of aortic regurgitation; incidence of aortic dissection, aortic root surgery, and death; progression of mitral regurgitation; left ventricular size and function; echocardiographically derived measures of central aortic stiffness; skeletal and somatic growth; and incidence of adverse drug reactions.

CONCLUSION

This randomized trial should make a substantial contribution to the management of individuals with MFS and expand our understanding of the mechanisms responsible for the aortic manifestations of this disorder.

Spinal deformities in Marfan syndrome

Marfan syndrome is a connective tissue disease that affects the skeletal system among other organ systems. Kyphoscoliosis, spondylolisthesis, and atlantoaxial subluxation are common spinal deformities in Marfan syndrome, and distinctive vertebral morphology within such patients presents significant treatment challenges. Although most scoliosis curves in patients who have Marfan syndrome are minor, those that require treatment progress rapidly; brace treatment has proven ineffective for most patients. Surgical correction is associated with complications, such as failure of fixation and additional deformity; however good results are possible when consideration is given to the unique challenges presented by patients who have Marfan syndrome.

Aortic Diameter ≥5.5 cm Is Not a Good Predictor of Type A Aortic Dissection

Background— Studies of aortic aneurysm patients have shown that the risk of rupture increases with aortic size. However, few studies of acute aortic dissection patients and aortic size exist. We used data from our registry of acute aortic dissection patients to better understand the relationship between aortic diameter and type A dissection.

Methods and Results— We examined 591 type A dissection patients enrolled in the International Registry of Acute Aortic Dissection between 1996 and 2005 (mean age, 60.8 years). Maximum aortic diameters averaged 5.3 cm; 349 (59%) patients had aortic diameters <5.5 cm and 229 (40%) patients had aortic diameters <5.0 cm. Independent predictors of dissection at smaller diameters (<5.5 cm) included a history of hypertension (odds ratio, 2.17; 95% confidence interval, 1.03 to 4.57; P =0.04), radiating pain (odds ratio, 2.08; 95% confidence interval, 1.08 to 4.0; P =0.03), and increasing age (odds ratio, 1.03; 95% confidence interval, 1.00 to 1.05; P =0.03). Marfan syndrome patients were more likely to dissect at larger diameters (odds ratio, 14.3; 95% confidence interval, 2.7 to 100; P =0.002). Mortality (27% of patients) was not related to aortic size.

Conclusions— The majority of patients with acute type A acute aortic dissection present with aortic diameters <5.5 cm and thus do not fall within current guidelines for elective aneurysm surgery. Methods other than size measurement of the ascending aorta are needed to identify patients at risk for dissection.

Effect of mutation type and location on clinical outcome in 1,013 probands with Marfan syndrome or related phenotypes and FBN1 mutations: an international study

Mutations in the fibrillin-1 (FBN1) gene cause Marfan syndrome (MFS) and have been associated with a wide range of overlapping phenotypes. Clinical care is complicated by variable age at onset and the wide range of severity of aortic features. The factors that modulate phenotypical severity, both among and within families, remain to be determined. The availability of international FBN1 mutation Universal Mutation Database (UMD-FBN1) has allowed us to perform the largest collaborative study ever reported, to investigate the correlation between the FBN1 genotype and the nature and severity of the clinical phenotype. A range of qualitative and quantitative clinical parameters (skeletal, cardiovascular, ophthalmologic, skin, pulmonary, and dural) was compared for different classes of mutation (types and locations) in 1,013 probands with a pathogenic FBN1 mutation. A higher probability of ectopia lentis was found for patients with a missense mutation substituting or producing a cysteine, when compared with other missense mutations. Patients with an FBN1 premature termination codon had a more severe skeletal and skin phenotype than did patients with an inframe mutation. Mutations in exons 24-32 were associated with a more severe and complete phenotype, including younger age at diagnosis of type I fibrillinopathy and higher probability of developing ectopia lentis, ascending aortic dilatation, aortic surgery, mitral valve abnormalities, scoliosis, and shorter survival; the majority of these results were replicated even when cases of neonatal MFS were excluded. These correlations, found between different mutation types and clinical manifestations, might be explained by different underlying genetic mechanisms (dominant negative versus haploinsufficiency) and by consideration of the two main physiological functions of fibrillin-1 (structural versus mediator of TGF beta signalling). Exon 24-32 mutations define a high-risk group for cardiac manifestations associated with severe prognosis at all ages.

Etiology, pathogenesis and management of thoracic aortic aneurysm

Given the growing proportion of elderly people in Western societies and the increasing prevalence of chronic hypertension, the management of aneurysmal aortic disease is an ever growing challenge. Although degenerative changes in the aortic wall are common to thoracic aortic aneurysm (TAA) and to various types of dissection in general, TAA can result from specific heritable disorders of connective tissues. Today, increased awareness of vascular diseases and access to tomographic imaging equipment facilitate the diagnosis of TAA, even when asymptomatic. While most TAA cases with ascending aortic involvement are treated with surgical repair (primarily valve-preserving techniques), aneurysms of the distal arch and descending thoracic aorta are amenable to alternatives to classic open repair such as the emerging endovascular treatment techniques. In this Review, we provide a comprehensive overview of the etiology, pathophysiology and clinical management of patients with TAA, and discuss the most recent literature on the condition.

Whole genome expression profiling reveals a significant role for immune function in human abdominal aortic aneurysms

BACKGROUND

Abdominal aortic aneurysms are a common disorder with an incompletely understood etiology. We used Illumina and Affymetrix microarray platforms to generate global gene expression profiles for both aneurysmal (AAA) and non-aneurysmal abdominal aorta, and identified genes that were significantly differentially expressed between cases and controls.

RESULTS

Affymetrix and Illumina arrays included 18,057 genes in common; 11,542 (64%) of these genes were considered to be expressed in either aneurysmal or normal abdominal aorta. There were 3,274 differentially expressed genes with a false discovery rate (FDR) </= 0.05. Many of these genes were not previously known to be involved in AAA, including SOST and RUNX3, which were confirmed using Q-RT-PCR (Pearson correlation coefficient for microarray and Q-RT-PCR data = 0.89; p-values for differences in expression between AAA and controls for SOST: 4.87 x 10-4 and for RUNX3: 4.33 x 10-5). Analysis of biological pathways, including Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG), indicated extreme overrepresentation of immune related categories. The enriched categories included the GO category Immune Response (GO:0006955; FDR = 2.1 x 10-14), and the KEGG pathways natural killer cell mediated cytotoxicity (hsa04650; FDR = 5.9 x 10-6) and leukocyte transendothelial migration (hsa04670; FDR = 1.1 x 10-5).

CONCLUSION

Previous studies have provided evidence for the involvement of the immune system in AAA. The current expression analysis extends these findings by demonstrating broad coordinate gene expression in immunological pathways. A large number of genes involved in immune function were differentially expressed in AAA, and the pathway analysis gave these results a biological context. The data provide valuable insight for future studies to dissect the pathogenesis of human AAA. These pathways might also be used as targets for the development of therapeutic agents for AAA.

Remodeling of vaginal connective tissue in patients with prolapse

PURPOSE OF REVIEW

Pelvic organ prolapse is a common disease that negatively affects the lives of women. To date, basic science research into the pathogenesis of prolapse has been limited. The vagina and its supportive connective tissues provide one of the primary mechanisms of support to the pelvic organs. This review summarizes our current understanding of the alterations in these tissues in women with prolapse.

RECENT FINDINGS

Current research suggests that the vagina and its supportive tissues actively remodel in response to different environmental stimuli. The literature has many shortcomings due to restricted access to tissue, absence of longitudinal data, and limited animal models. Nevertheless, recent studies indicate that within prolapsed tissue metabolism of collagen and elastin is altered. Thus, not only the synthesis of those structural proteins but also the balance between the activity of the major proteolytic enzymes that degrade them and the inhibitors of proteolysis are important components to consider in studies on the pathogenesis of pelvic organ prolapse.

SUMMARY

Biochemical studies of the vagina and its supportive connective tissues have improved understanding of the contribution of altered connective tissue to the pathogenesis of prolapse. It is important to continue research in this area, as the knowledge gained from these studies will allow for the development of innovative reconstructive procedures and the establishment of preventive measures.

Homozygosity for a FBN1 missense mutation: clinical and molecular evidence for recessive Marfan syndrome

Marfan syndrome (MFS) is known as an autosomal-dominant connective tissue disorder (MIM 154,700), involving primarily the skeletal, ocular and cardiovascular systems, and caused by mutations in the gene for fibrillin1 (FBN1). Here, we report on two cousins from a consanguineous family with a homozygous c.1,453C>T FBN1 mutation (p.Arg485Cys) and MFS. All four healthy parents were heterozygous for the c.1,453C>T FBN1 mutation and none fulfilled the Ghent criteria for MFS. This family is the first molecularly confirmed recessive MFS. The demonstration of recessive cases of MFS has obvious implications for genetic counselling as well as for molecular diagnosis.

Transclival cerebrospinal fluid fistula in a patient with Marfan's syndrome

Marfan's syndrome is a disease associated with reduced structural integrity of connective tissues. We report a 36-year-old patient with Marfan's syndrome who presented with rhinorrhoea, occipital headache and vomiting. Physical examination revealed typical Marfan's syndrome features including dolicocephalous, mandibular micrognathia, tall stature, disproportionately long limbs and digits, and hypermobility of the joints. A high-resolution CT scan demonstrated pneumoencephalous, cerebrospinal fluid (CSF) filling the sphenoidal sinus, and a small bone defect of the clivus. Surgery performed through a transsphenoidal approach revealed the sphenoid sinus to be filled with CSF and a small fenestration in the clivus. The arachnoid diverticulum and the fenestration were repaired and covered with a graft of abdominal fat. In this patient, a deficiency in bone development associated with Marfan's syndrome gave rise to a clival fenestration and a transclival CSF fistula. Although abnormalities of the spinal meningeal membranes have been reported in Marfan's syndrome, to our knowledge, this is the first report of a fistula located in the cranial base in this condition.

Searching for subtle features of laxity of connective tissue in patients with ruptured intracranial aneurysms: a pilot study

BACKGROUND

A disruption of the extracellular matrix (ECM) of the intracranial arterial wall is a likely contributing factor in the pathogenesis of intracranial aneurysms. If this is a generalized process, patients with subarachnoid haemorrhage (SAH) may have subtle signs of a general laxity of the connective tissue. We performed a pilot study to assess general laxity in SAH patients and to examine which tests for joint mobility can be best used in these patients.

METHODS

In 59 SAH patients and sex- and age-matched controls we compared: (1) joint mobility (scores of Beighton and Bulbena and the total range of joint motion); (2) skin extensibility, and (3) bone quantity and stiffness. For the analyses we used the independent-samples T test and linear regression with adjustment for possible confounders.

RESULTS

The patients had a higher degree of joint mobility according to the Beighton criteria (total score of 4 in patients vs. 2 in controls, p = 0.001) and the summation of Z scores of active range of motion measurements (0.1 in patients vs. -0.1 in controls, p = 0.0036), and a tendency towards a higher degree of joint mobility according to the Bulbena criteria (total score of 3 in patients vs. 2 in controls, p = 0.097) and the summation of active range of joint motion measurements (1,292 in patients vs. 1,275 in controls, p = 0.13). No differences were found for the other investigated characteristics.

CONCLUSIONS

Our preliminary results suggest that SAH patients have a higher degree of joint mobility than controls. The Beighton score can be best used in our patient population.

Familial neonatal Marfan syndrome due to parental mosaicism of a missense mutation in the FBN1 gene

We present a family in which three siblings were born with neonatal Marfan syndrome (MFS) to unaffected parents. The clinical findings included joint contractures, large ears, loose skin, ectopia lentis, muscular hypoplasia, aortic root dilatation, mitral and tricuspid valve insufficiency, and pulmonary emphysema. All three siblings died due to cardiorespiratory insufficiency by 2-4 months of age. Screening of the FBN1 gene showed the heterozygous c.3257G > A (p.Cys1086Tyr) mutation in the proband. Mosaicism of the mutation was demonstrated in the somatic cells and in the germ line of the father. Although three examples of parental mosaicism for classical MFS were demonstrated previously, this is the first report of familial occurrence of neonatal MFS due to a heterozygous mutation in FBN1. In conclusion, the p.Cys1086Tyr mutation in FBN1 is consistently associated with neonatal MFS. Parental mosaicism should always be kept in mind when counseling families with MFS.

Large genomic fibrillin-1 (FBN1) gene deletions provide evidence for true haploinsufficiency in Marfan syndrome

Mutations in the FBN1 gene are the major cause of Marfan syndrome (MFS), an autosomal dominant connective tissue disorder, which displays variable manifestations in the cardiovascular, ocular, and skeletal systems. Current molecular genetic testing of FBN1 may miss mutations in the promoter region or in other noncoding sequences as well as partial or complete gene deletions and duplications. In this study, we tested for copy number variations by successively applying multiplex ligation-dependent probe amplification (MLPA) and the Affymetrix Human Mapping 500 K Array Set, which contains probes for approximately 500,000 single-nucleotide polymorphisms (SNPs) across the genome. By analyzing genomic DNA of 101 unrelated individuals with MFS or related phenotypes in whom standard genetic testing detected no mutation, we identified FBN1 deletions in two patients with MFS. Our high-resolution approach narrowed down the deletion breakpoints. Subsequent sequencing of the junctional fragments revealed the deletion sizes of 26,887 and 302,580 bp, respectively. Surprisingly, both deletions affect the putative regulatory and promoter region of the FBN1 gene, strongly indicating that they abolish transcription of the deleted allele. This expectation of complete loss of function of one allele, i.e. true haploinsufficiency, was confirmed by transcript analyses. Our findings not only emphasize the importance of screening for large genomic rearrangements in comprehensive genetic testing of FBN1 but, importantly, also extend the molecular etiology of MFS by providing hitherto unreported evidence that true haploinsufficiency is sufficient to cause MFS.

Marfan syndrome: from molecular pathogenesis to clinical treatment

Marfan syndrome is a connective tissue disorder with ocular, musculoskeletal and cardiovascular manifestations that are caused by mutations in fibrillin-1, the major constituent of extracellular microfibrils. Mouse models of Marfan syndrome have revealed that fibrillin-1 mutations perturb local TGFbeta signaling, in addition to impairing tissue integrity. This discovery has led to the identification of a new syndrome with overlapping Marfan syndrome-like manifestations that is caused by mutations in TGFbeta receptor types I and II. It has also prompted the idea that TGFbeta antagonism will be a productive treatment strategy in Marfan syndrome and perhaps in other related disorders. More generally, these studies have established that Marfan syndrome is part of a group of developmental disorders with broad and complex effects on morphogenesis, homeostasis and organ function.

Asthma and airways collapse in two heritable disorders of connective tissue

OBJECTIVES

This study investigated the clinical impression that there was an increased prevalence of respiratory disorders in both the Hypermobility Syndrome (HMS)/Benign Joint Hypermobility Syndrome (BJHS) and Ehlers-Danlos Syndrome (EDS), compared with the normal population.

METHODS

A questionnaire was distributed to 509 subjects (221 healthy controls, 126 HMS, 162 EDS) who documented respiratory symptoms and previously diagnosed respiratory and atopic disorders. A subgroup of 157 responders underwent full clinical and serological assessments, and 57 subjects were assessed physiologically.

RESULTS

A significant increase in the frequency of a wide range of respiratory symptoms and reduced exercise tolerance was observed in subjects with both HMS and EDS compared with controls. In particular, there was an increased prevalence of asthmatic symptoms (HMS: OR 2.4, 95% CI 1.4-4.1, p = 0.002; EDS: OR 3.1, 95% CI 1.8-5.2, p<0.001) and atopy (HMS: OR 2.7, 95% CI 1.6-4.5, p<0.001; EDS: OR 2.6, 95% CI 1.6-4.4, p<0.001), which was subsequently confirmed by clinical assessment. Pulmonary physiological studies revealed increased lung volumes, impaired gas exchange and an increased tendency of both the lower and upper airways to collapse.

CONCLUSIONS

We have demonstrated, for the first time, that individuals with HMS/BJHS and EDS have respiratory symptoms in association with various pulmonary physiological abnormalities. The increased prevalence of asthma may be due to linkage disequilibrium between the genes causing these conditions or a function of the connective tissue defect itself. In the non-asthmatic population, changes in the mechanical properties of the bronchial airways and lung parenchyma may underlie the observed increased tendency of the airways to collapse.

Marfan's syndrome and the heart

In recent years, there have been many advances in the treatment of cardiac disease in children with Marfan's syndrome. Early diagnosis, meticulous echocardiographic follow-up and multidisciplinary assessment are essential. Medical treatment with beta-blockers is probably helpful in most children with aortic root dilatation. Research on TGFbeta signalling and the potential treatment role of TGFbeta antagonists may lead to exciting new treatments, but the results of clinical trials are awaited. In managing the cardiovascular complications of Marfan's syndrome, the paediatrician has to walk a difficult path. On the one hand, restrictive lifestyle advice and drugs may need to be prescribed, often in the context of a family history of major surgery or even sudden death. On the other hand, it is essential to encourage the often asymptomatic child to develop and mature as normally as possible.

Symposium on the musculoskeletal aspects of Marfan syndrome: meeting report and state of the science

The National Marfan Foundation sponsored a symposium in August 2005 to review recent progress in the area of Marfan-related musculoskeletal research. Orthopaedic surgeons, molecular geneticists, medical geneticists, and pain specialists met to review a variety of topics. This report reviews and summarizes the proceedings of the symposium, with emphasis on future directions for study that were identified in the course of the meeting. Areas covered include clinical detection, diagnosis, growth, spine deformity, molecular mechanisms, dural ectasia, protrusio acetabuli, and pain in Marfan syndrome.

Aortic root disease in tetralogy of Fallot

PURPOSE OF REVIEW

Progressive aortic root dilatation is a recognized feature of tetralogy of Fallot even in patients following initial reparative surgery. The underlying pathophysiology was initially attributed to altered hemodynamics resulting from longstanding volume overloading and stretching of the aortic root from increased right to left shunting. This review explores the pathophysiology and possible mechanisms for the aortic dilatation, and whether these changes are a reflection of the initial hemodynamic stress or a cellular expression of an unrecognized gene associated with conotruncal defects.

RECENT FINDINGS

The recent publication of two case reports of aortic aneurysm and dissection in tetralogy of Fallot patients re-emphasized the fact that aortic root dilatation can no longer be regarded as a benign problem in tetralogy of Fallot patients. Findings of intrinsic histological abnormalities in the aortic root and ascending aorta of tetralogy of Fallot patients suggest that intrinsic abnormalities may also play an important causative role.

SUMMARY

A better understanding of the pathophysiology will help to formulate future treatment and management strategies in the subgroup of tetralogy of Fallot patients with progressive aortic dilatation.

Perturbations of vascular homeostasis and aortic valve abnormalities in fibulin-4 deficient mice

The Fibulins are a 6-member protein family hypothesized to function as intermolecular bridges that stabilize the organization of extracellular matrix structures. Here, we show that reduced expression of Fibulin-4 leads to aneurysm formation, dissection of the aortic wall and cardiac abnormalities. Fibulin-4 knockdown mice with a hypomorphic expression allele arose from targeted disruption of the adjacent Mus81 endonuclease gene. Mice homozygous for the Fibulin-4 reduced expression allele (Fibulin-4(R/R)) show dilatation of the ascending aorta and a tortuous and stiffened aorta, resulting from disorganized elastic fiber networks. They display thickened aortic valvular leaflets that are associated with aortic valve stenosis and insufficiency. Strikingly, already a modest reduction in expression of Fibulin-4 in the heterozygous Fibulin-4(+/R) mice occasionally resulted in small aneurysm formation. To get insight into the underlying molecular pathways involved in aneurysm formation and response to aortic failure, we determined the aorta transcriptome of Fibulin-4(+/R) and Fibulin-4(R/R) animals and identified distinct and overlapping biological processes that were significantly overrepresented including cytoskeleton organization, cell adhesion, apoptosis and several novel gene targets. Transcriptome and protein expression analysis implicated perturbation of TGF-beta signaling in the pathogenesis of aneurysm in fibulin-4 deficient mice. Our results show that the dosage of a single gene can determine the severity of aneurysm formation and imply that disturbed TGF-beta signaling underlies multiple aneurysm phenotypes.

Early Surgical Experience With Loeys-Dietz: A New Syndrome of Aggressive Thoracic Aortic Aneurysm Disease

BACKGROUND

Loeys-Dietz syndrome (LDS) is a recently described genetic aortic aneurysm syndrome resulting from mutations in receptors for the cytokine transforming growth factor-beta. Phenotypic features include a bifid uvula, hypertelorism, cleft palate, and generalized arterial tortuosity, but risk of thoracic aortic rupture and dissection is the principle focus of management and exceeds that of most known connective tissue disorders. Our surgical experience with LDS was reviewed to assess outcomes and develop guidelines for management of this aggressive disease.

METHODS

We retrospectively reviewed medical records of all LDS patients from two institutions and obtained follow-up data from medical records and patient contacts.

RESULTS

Clinical criteria and genotyping were used to identify 71 patients. Before surgical intervention, 6 patients (9%) died from aneurysm rupture or dissection, which occurred in several patients with aortic diameters of less than 4.5 cm and as early as 6 months of age. Thoracic aortic aneurysm surgery was performed in 14 children and 7 adults. Operations included valve-sparing root replacement (VSRR) in 13, Bentall procedure in 5, arch replacement in 2, and VSRR with arch replacement in 1. There were no deaths at the primary operation, although 3 patients died 2, 5, and 11 years after surgery from rupture of the descending thoracic (n = 2) or abdominal aorta (n = 1).

CONCLUSIONS

LDS is an aggressive aortic aneurysm disease with a propensity toward rupture and dissection at a younger age and smaller aortic diameters than in other connective tissue disorders, particularly in the ascending aorta. Early recognition of the phenotype, prophylactic intervention, and meticulous surveillance of the distal aorta and vascular tree are warranted for optimal management.

Tendon and ligament injuries: the genetic component

Tendons and ligaments within the upper and lower limbs are some of the more common sites of musculoskeletal injuries during physical activity. Several extrinsic and intrinsic factors have been shown to be associated with these injuries. More recently, studies have suggested that there is also, at least in part, a genetic component to the Achilles tendon, rotator cuff and anterior cruciate ligament injuries. However, specific genes have not been suggested to be associated with rotator cuff or anterior cruciate ligament injuries. Sequence variants of the tenascin C (TNC) gene, on the other hand, have been shown to be associated with Achilles tendinopathies and Achilles tendon ruptures, whereas a variant of the collagen V alpha 1 (COL5A1) gene has also been shown to be associated with Achilles tendinopathies. Both genes encode for important structural components of tendons and ligaments. The COL5A1 gene encodes for a component of type V collagen, which has an important role in regulating collagen fibre assembly and fibre diameters. The TNC gene, on the other hand, encodes for TNC, which regulates the tissue's response to mechanical load. To date, only variants in two genes have been shown to be associated with Achilles tendon injuries. In addition, although specific genes have not been identified, investigators have suggested that there is also a genetic component to both rotator cuff and anterior cruciate ligament injuries. In future, specific genotypes associated with increased risk of injury to specific tendons and ligaments can prevent these injuries by identifying individuals at higher risk.

LTBP-2 specifically interacts with the amino-terminal region of fibrillin-1 and competes with LTBP-1 for binding to this microfibrillar protein

LTBP-2 is a matrix protein of unknown function since, unlike other LTBPs, it does not form covalent complexes with latent TGF-beta. We have previously shown that LTBP-2 has widespread association with fibrillin-containing microfibrils in developing aorta and other tissues. We have now shown that full-length human recombinant LTBP-2 specifically binds to the amino-terminal region of fibrillin-1, but not to fibrillin-2, in solid phase assays and overlay blotting. The binding was enhanced by the inclusion of 2 mM Ca2+ ions in the assay buffer and abolished by 5 mM EDTA indicating that the interaction was directly or indirectly Ca2+ ion dependent. The K(d) for the interaction was calculated from the specific binding curve as 9.4 nM. A recombinant carboxyl-terminal fragment of LTBP-2 was shown to a) bind the amino-terminal fragment of fibrillin-1 and b) block completely the binding of full length LTBP-2 to fibrillin-1. This result indicates that the major fibrillin-1 binding site resides close to the carboxyl-terminus of LTBP-2. Further competitive binding studies showed that an analogous carboxyl terminal fragment of LTBP-1 was able to block the binding of LTBP-2 to fibrillin-1 and that the C-terminal fragment of LTBP-2 could block the interaction of the LTBP-1 fragment with the fibrillin. Thus the binding site for LTBP-2 on fibrillin-1 appears to be the same or in close proximity to that for LTBP-1. Immunohistochemical analysis of developing human aorta showed distinctive but extensively overlapping distributions for LTBPs-1 and -2. Both LTBPs showed extensive co-localization with fibrillin-1 and elastic lamellae but LTBP-2 had extensive signal throughout the medial layer whereas LTBP-1 showed strong localization only in the outer medial layer. The finding indicates that there is a possibility for LTBP-2 to compete with LTBP-1 for binding to fibrillin-containing microfibrils throughout the aortic wall but particularly in the outer medial region where the LTBP-1 is predominantly located. Overall, the results support the concept that that LTBP-2 may be an indirect negative modulator for storage of the large latent TGF-beta complex on microfibrils in aorta and other fibrillin-rich tissues.

A Japanese family of typical Loeys-Dietz syndrome with a TGFBR2 mutation

This report describes a Japanese family with vessel and craniofacial abnormalities. Although the clinical findings of the patient's father fulfilled the diagnostic criteria for Marfan syndrome, arterial tortuosity, aneurysms, hypertelorism and a bifid uvula were noted in both the patient and his father. These findings were compatible with the clinical manifestations that were previously reported in Loeys-Dietz syndrome. A molecular genetic analysis demonstrated a heterozygous missense mutation of the transforming growth factor-beta receptor II gene in both the patient and his father, which thus caused Loeys-Dietz syndrome. This is the first Japanese family case report of typical Loeys-Dietz syndrome.

Multi-exon out of frame deletion of the FBN1 gene leading to a severe juvenile onset cardiovascular phenotype in Marfan syndrome

Marfan syndrome is caused by mutations in fibrillin-1, a large gene spanning approximately 200 kb of genomic DNA on chromosome 15q21. So far, more than 600 different mutations have been identified, accounting for 60-90% of all Marfan syndrome cases, the vast majority being single nucleotide exchanges as well as small deletions and insertions. Only four major rearrangements have been described in the literature so far. We have screened 11 individuals fulfilling the diagnostic criteria of Marfan syndrome but negative for point mutations in the fibrillin-1 gene by SSCP and/or direct sequencing, for large rearrangements. We report here the largest known de novo and out of frame deletion in the fibrillin-1 gene in a patient fulfilling the diagnostic criteria of Marfan syndrome. We identified the deletion breakpoints at the genomic and transcript levels and studied the expression of the mutated allele at the transcript and protein level. We conclude that large rearrangements may account for a non-negligible proportion of all Marfan cases.

What mouse mutants teach us about extracellular matrix function

For many years the extracellular matrix was viewed as a benign scaffold for arranging cells within connective tissues, but it is now being redefined as a dynamic, mobile, and flexible key player in defining cellular behavior. Gene targeting, transgene expression, and spontaneous mutations of extracellular matrix proteins in mice have greatly accelerated our mechanistic view of the structural and instructive functions of the extracellular matrix in developmental and regenerative processes. This review summarizes the phenotypes of genetic mouse models carrying mutations in extracellular matrix proteins, with specific emphasis on recent advances. The application of reverse genetics has demonstrated the multifunctionality of matrix proteins in a biological context and, in addition, has brought a novel perspective to the understanding of human pathologies.

Coronary artery aneurysms in patients with hyper IgE recurrent infection syndrome

Hyper IgE recurrent infection syndrome (HIES, or Job's syndrome) is a primary immunodeficiency characterized by recurrent skin and lung infections, eczema, elevated serum immunoglobulin E (IgE) levels, and various connective tissue and skeletal system abnormalities including characteristic facies, scoliosis, joint hyperextensibility, retained primary dentition, craniosynostosis, osteopenia, and pathologic fractures. We have identified two patients with aneurysmal coronary artery disease. One was a forty-three-year-old man with HIES and coronary artery aneurysms and ectasia identified on cardiac catheterization following myocardial infarction. The other was a 48-year-old man with coronary artery ectasia-aneurysm identified after cardiac catheterization for evaluation of chest pain. Although connective tissue abnormalities are common in HIES, this is the first report of coronary artery aneurysms in HIES. Further studies are necessary to determine the incidence, pathogenesis, and optimal therapy of these arterial abnormalities in HIES.

Macular degeneration: recent advances and therapeutic opportunities

The central retina mediates high acuity vision, and its progressive dysfunction due to macular degeneration is the leading cause of visual disability among adults in industrialized societies. Here, we summarize recent progress in understanding the pathophysiology of macular degeneration and the implications of this new knowledge for treatment and prevention. The past decade has witnessed remarkable advances in this field, including the development of new, non-invasive retinal imaging technologies, the development of animal models for macular disease, and the isolation of many of the genes responsible for both early- and late-onset macular diseases. These advances have set the stage for the development of effective mechanism-based therapies.

Different patterns of aortic wall elasticity in patients with Marfan syndrome: A noninvasive follow-up study

OBJECTIVE

Aortic complications determine the life expectancy of most patients with Marfan syndrome. To find out whether there is heterogenous aortic involvement among patients and, if there is, to characterize aortic patterns and response to long-term beta-blocker therapy, we investigated aortic elastic properties before and during beta-blocker treatment.

METHODS

In 46 patients with Marfan syndrome (age, 17.4 +/- 11.1 years) and 46 healthy control subjects, ascending and descending aortic elastic parameters were determined noninvasively before and after 39 +/- 16 months of beta-blocker treatment with atenolol.

RESULTS

Aortic diameters and distensibility distinguished Marfan patients and controls with a sensitivity of 85% and a specificity of 87%. Cluster analysis revealed 4 patterns of aortic phenotypic expression: (1) reduced ascending aortic elasticity (46% of patients), (2) diminished ascending and descending aortic elasticity (17%), (3) minimal alterations of ascending and descending aortic elasticity (20%), and (4) reduced descending aortic elasticity (17%). During follow-up, aortic elastic properties improved in 21 (70%) of 30 patients and deteriorated in 9 (30%) irrespective of beta-blocker dosage. Improvement was observed in 100% of patients (n = 7; age, 5.3 +/- 4.2 years) with end-diastolic aortic root diameters between 20 and 30 mm and in 61% of patients (14/23; age, 20.5 +/- 10.0 years) with root diameters between 30 and 52 mm.

CONCLUSIONS

Aortic elastic parameters distinguish between patients with Marfan syndrome and healthy controls and show the pattern of regional aortic involvement. Improvement or deterioration during follow-up can influence therapeutic decisions to prevent aortic dissection and rupture. Young age, small root diameter, and high distensibility are favorable prognostic factors.

Cardiovascular management of marfan syndrome in the young

Marfan syndrome is an autosomal-dominant disorder of connective tissue resulting from a mutation in the fibrillin gene. Manifestations of the disorder primarily affect the skeletal, cardiovascular, and ocular systems. The phenotypic manifestations of this disorder can be quite variable. The major cause of morbidity and mortality in this patient population is the cardiovascular manifestations of the disorder: aortic root dilation and dissection. Individuals with this disorder are at risk for catastrophic cardiovascular events, most often as a result of aortic dissection. Although the incidence of dissection in childhood is exceedingly low, the background of a progressively dilating aortic root appears to be the major factor contributing to this risk in adulthood. Therefore, it is beneficial to identify affected individuals as early as possible to institute lifestyle changes and medical therapy in an effort to enhance their long-term outcome. Familial screening, once a case has been identified, and consideration of genetic screening of an affected family may also be helpful. Medical therapy with beta blockers, calcium channel blockers, and/or angiotensin inhibitors has been shown to be somewhat effective in slowing the rate of growth of the aorta. Exciting new data suggest that angiotensin II receptor antagonists may provide an even greater degree of protection from aortic dilatation in this population. Despite medical therapy, patients with Marfan syndrome do have progressive dilatation of their aortic root. The risk of aortic dissection increases with increasing size of the aorta. Prophylactic surgical techniques have been successful in reducing the morbidity and mortality associated with aortic dissection, resulting in a longer average life span in this patient population.

Aneurysm syndromes caused by mutations in the TGF-beta receptor

BACKGROUND

The Loeys-Dietz syndrome is a recently described autosomal dominant aortic-aneurysm syndrome with widespread systemic involvement. The disease is characterized by the triad of arterial tortuosity and aneurysms, hypertelorism, and bifid uvula or cleft palate and is caused by heterozygous mutations in the genes encoding transforming growth factor beta receptors 1 and 2 (TGFBR1 and TGFBR2, respectively).

METHODS

We undertook the clinical and molecular characterization of 52 affected families. Forty probands presented with typical manifestations of the Loeys-Dietz syndrome. In view of the phenotypic overlap between this syndrome and vascular Ehlers-Danlos syndrome, we screened an additional cohort of 40 patients who had vascular Ehlers-Danlos syndrome without the characteristic type III collagen abnormalities or the craniofacial features of the Loeys-Dietz syndrome.

RESULTS

We found a mutation in TGFBR1 or TGFBR2 in all probands with typical Loeys-Dietz syndrome (type I) and in 12 probands presenting with vascular Ehlers-Danlos syndrome (Loeys-Dietz syndrome type II). The natural history of both types was characterized by aggressive arterial aneurysms (mean age at death, 26.0 years) and a high incidence of pregnancy-related complications (in 6 of 12 women). Patients with Loeys-Dietz syndrome type I, as compared with those with type II, underwent cardiovascular surgery earlier (mean age, 16.9 years vs. 26.9 years) and died earlier (22.6 years vs. 31.8 years). There were 59 vascular surgeries in the cohort, with one death during the procedure. This low rate of intraoperative mortality distinguishes the Loeys-Dietz syndrome from vascular Ehlers-Danlos syndrome.

CONCLUSIONS

Mutations in either TGFBR1 or TGFBR2 predispose patients to aggressive and widespread vascular disease. The severity of the clinical presentation is predictive of the outcome. Genotyping of patients presenting with symptoms like those of vascular Ehlers-Danlos syndrome may be used to guide therapy, including the use and timing of prophylactic vascular surgery.

Expression of matrix metalloproteinases and endogenous inhibitors within ascending aortic aneurysms of patients with Marfan syndrome

BACKGROUND

Marfan syndrome (MFS) is known to cause ascending thoracic aortic aneurysms (ATAAs). Transforming growth factor beta (TGF-beta) has recently been implicated in this process. Imbalances between the matrix metalloproteinases (MMPs) and their endogenous inhibitors (TIMPs) have also been shown to contribute to aneurysm formation. Whether and to what degree MMP, TIMP, and TGF-beta signaling profiles are altered in ATAAs in MFS compared with non-MFS patients remains unknown.

METHODS AND RESULTS

ATAA samples taken during aortic replacement from age-matched MFS (n=9) and non-MFS (n=18) patients were assessed for representative subtypes of all MMP classes, all 4 known TIMPs, and type 2 TGF-beta receptors (TGFBR2). Results were expressed as a percentage (mean+/-SEM) of reference control samples (100%; n=18) obtained from patients without ATAA. In MFS, decreased MMP-2 (76+/-7; P<0.05 versus control), increased MMP-12 (161+/-27% versus control; P<0.05), and increased MT1-MMP (248+/-64% versus 91+/-21 non-MFS and control; P<0.05) were observed. TIMP-3 (74+/-23%) was reduced compared with control values (P<0.05) and TIMP-2 was elevated (128+/-31%) compared with non-MFS (73+/-19%; P<0.05). In non-MFS samples, MMP-1 (70+/-16%), MMP-3 (77+/-18%), MMP-8 (75+/-11%), MMP-9 (69+/-14%), and MMP-12 (85+/-15%) were decreased compared with control (P<0.05). TIMPs 1 to 3 were reduced in non-MFS compared with control values (P<0.05). TGFBR2 were increased in MFS (193+/-32%) compared with non-MFS (95+/-16%) and controls (P<0.05).

CONCLUSIONS

A unique MMP and TIMP portfolio was observed in ATAAs from MFS compared with non-MFS patients. In addition, MFS samples showed evidence of increased TGF-beta signaling. These differences suggest disparate mechanisms of extracellular matrix remodeling between these 2 groups of patients.

Successful kidney transplantation from donor with Marfan's syndrome

Marfan's syndrome is caused by mutations in the extracellular matrix protein fibrillin-1 with aortic aneurysm and dissection being its most life-threatening manifestations. Kidney transplantation from donors with Marfan's syndrome has never been reported in the literature, possibly because of reticences due to the underlying connective tissue disease. Here, we report two patients with end-stage renal disease, transplanted with the kidneys from a donor with Marfan's syndrome who died of aortic dissection and cerebral hemorrhage. After delayed graft function in both recipients, renal function normalized with no renovascular complications and negative proteinuria for 6 years in one patient and 2 years in the other patient, who died from an ischemic cerebrovascular insult. Kidneys from organ donors with Marfan's syndrome might be suitable for transplantation.

Unusual rapid evolution of type B aortic dissection in a marfan patient following heart transplantation: successful endovascular treatment

A patient with Marfan syndrome with previous Bentall operation for mitral and tricuspid valve repair, required orthotopic cardiac transplantation for end stage cardiomyopathy. Postoperatively he suffered type-B aortic dissection, despite normal aortic diameters. Following sudden increase of aortic diameters, two years later, he underwent successful stent graft implantation. In patients with Marfan syndrome, post transplantation morbidity is high, with a 40% incidence of thoracic aortic dissection. This case highlights the potential of endovascular approach for treating post-transplantation aortic dissection.

Spectrum of Aortic Operations in 300 Patients With Confirmed or Suspected Marfan Syndrome

BACKGROUND

Cardiovascular disease is the main cause of morbidity and mortality in patients with Marfan syndrome. Many patients with presumed Marfan syndrome do not meet current diagnostic criteria. This study reviews the surgical aspects of aortic disease in 300 patients referred with the diagnosis of Marfan syndrome.

METHODS

During a 16-year period, 300 patients with presumed Marfan syndrome underwent 398 operations on the aorta and branch arteries, including 125 aortic root operations, 59 aortic arch repairs, 31 descending thoracic aortic repairs, and 178 thoracoabdominal aortic repairs. Based on medical record review, patients were classified as confirmed Marfan syndrome if documented features satisfied current diagnostic criteria; patients not meeting these criteria were classified as suspected Marfan syndrome.

RESULTS

There were 17 operative deaths (4.3%) after the 398 operations. Survival after the initial referral operation was 96.2% +/- 1.5% at 1 year, 82.7% +/- 2.4% at 5 years, and 74.6% +/- 3.1% at 10 years. Presentations, operative details, and outcomes were remarkably similar in the 137 patients (45.7%) with confirmed Marfan syndrome and the 163 patients (54.3%) with suspected Marfan syndrome. Freedom from repair failure, however, was significantly better in patients with confirmed Marfan syndrome (90.3% +/- 2.3% at 10 years) than in those with suspected Marfan syndrome (82.0% +/- 3.1% at 10 years; p = 0.001).

CONCLUSIONS

Operative treatment of the full spectrum of aortic disease in Marfan patients enables excellent long-term survival. Similarities in surgical aspects of aortic disease suggest that patients with features of Marfan syndrome who do not meet diagnostic criteria should be managed in the same manner as patients with confirmed Marfan syndrome.

Mutations of TGFbeta signaling molecules in human disease

The transforming growth factor beta (TGFbeta) signaling pathway regulates several biological processes including cellular proliferation, differentiation, apoptosis, migration, and extracellular matrix deposition. Ligand and receptor family members signal through two main Smad signaling branches, TGFbeta/activin to Smad2/3 (Sma and MAD-related proteins) and bone morphogenetic protein (BMP) to Smad1/5. At the molecular level, TGFbeta acts by modifying cytoskeletal organization and ultimately regulating expression of specific target genes. Germline disruption of TGFbeta signaling leads to several types of hereditary congenital malformation or dysfunction of the skeletal, muscular and/or cardiovascular systems, and to cancer predisposition syndromes. In this review, the molecular etiology of TGFbeta-associated disorders is examined, together with a discussion of clinical overlap between syndromes and possible biological explanations underlying the variable penetrance and expressivity of clinical characteristics. Increasing our understanding of the molecular etiology underlying genotype-phenotype correlations will ultimately provide a molecular-based approach that should result in better prognostic tools, smart therapeutics and individualized disease management, not only for these rare syndromes, but for more generalized disorders of the cardiovascular and musculoskeletal systems and cancer. The clinical consequence of TGFbeta signaling mutations appears to depend on environmental factors and on the basal levels of ongoing signaling transduction networks specific to each individual. In this respect, genetic background might be a central factor in determining disease outcome and treatment strategy for TGFbeta-associated diseases.