Basic defects in the Marfan syndrome

Targeted next-generation sequencing reveals the genetic mechanism of Chinese Marfan syndrome cohort with ocular manifestation

BACKGROUND

Marfan syndrome (MFS) is a hereditary connective tissue disorder involving multiple systems, including ophthalmologic abnormalities. Most cases are due to heterozygous mutations in the fibrillin-1 gene (FBN1). Other associated genes include LTBP2, MYH11, MYLK, and SLC2A10. There is significant clinical overlap between MFS and other Marfan-like disorders.

PURPOSE

To expand the mutation spectrum of FBN1 gene and validate the pathogenicity of Marfan-related genes in patients with MFS and ocular manifestations.

METHODS

We recruited 318 participants (195 cases, 123 controls), including 59 sporadic cases and 88 families. All patients had comprehensive ophthalmic examinations showing ocular features of MFS and met Ghent criteria. Additionally, 754 cases with other eye diseases were recruited. Panel-based next-generation sequencing (NGS) screened mutations in 792 genes related to inherited eye diseases.

RESULTS

We detected 181 mutations with an 84.7% detection rate in sporadic cases and 87.5% in familial cases. The overall detection rate was 86.4%, with FBN1 accounting for 74.8%. In cases without FBN1 mutations, 23 mutations from seven Marfan-related genes were identified, including four pathogenic or likely pathogenic mutations in LTBP2. The 181 mutations included 165 missenses, 10 splicings, three frameshifts, and three nonsenses. FBN1 accounted for 53.0% of mutations. The most prevalent pathogenic mutation was FBN1 c.4096G>A. Additionally, 94 novel mutations were detected, with 13 de novo mutations in 14 families.

CONCLUSION

We expanded the mutation spectrum of the FBN1 gene and provided evidence for the pathogenicity of other Marfan-related genes. Variants in LTBP2 may contribute to the ocular manifestations in MFS, underscoring its role in phenotypic diversity.

[Ocular manifestations of Marfan syndrome]

Marfan syndrome is an orphan disease that is caused by a mutation in the FBN1 gene located on chromosome 15 (15q21.1) and is usually inherited in an autosomal dominant manner. The article reviews the results of studies concerning the potential ocular manifestations of Marfan syndrome.

Viewing Victor McKusick's legacy through the lens of his bibliography

Victor McKusick's contributions to the field of medical genetics are legendary and include his contributions as a mentor, as creator of Mendelian Inheritance in Man (now Online Mendelian Inheritance in Man [OMIM®]), and as a leader in the field of medical genetics. McKusick's full bibliography includes 772 publications. Here we review the 453 papers authored by McKusick and indexed in PubMed, from his earliest paper published in the New England Journal of Medicine in 1949 to his last paper published in American Journal of Medical Genetics Part A in 2008. This review of his bibliography chronicles McKusick's evolution from an internist and cardiologist with an interest in genetics to an esteemed leader in the growing field of medical genetics. Review of his bibliography also provides a historical perspective of the development of the discipline of medical genetics. This field came into its own during his lifetime, transitioning from the study of interesting cases and families used to codify basic medical genetics principles to an accredited medical specialty that is expected to transform healthcare. Along the way, he helped to unite the fields of medical and human genetics to focus on mapping the human genome, culminating in completion of the Human Genome Project. This review confirms the critical role played by Victor McKusick as the founding father of medical genetics.

Aortic stiffness and distensibility in top-level athletes

BACKGROUND

Although cardiac adaptation to different sports has been extensively described, the potential relationship of training with aortic root (AR) elastic properties and diameters in top-level athletes remains not fully investigated. The aims of this study were to compare AR morphology and stiffness between highly trained athletes and sedentary subjects and to assess the independent determinants of AR stiffness and distensibility in athletes.

METHODS

Four hundred ten elite athletes (220 endurance-trained athletes [ATE] and 190 strength-trained athletes [ATS]; 290 men; mean age, 28.3 ± 13.6 years; age range, 18-40 years) and 240 healthy controls underwent standardized comprehensive transthoracic echocardiography, including Doppler studies. End-diastolic AR diameters were measured at four locations: the aortic annulus, the sinuses of Valsalva, the sinotubular junction, and the maximal diameter of the proximal ascending aorta. The aortic distensibility index was calculated as 2 × (systolic proximal ascending aortic diameter - diastolic proximal ascending aortic diameter)/(diastolic proximal ascending aortic diameter) × (pulse pressure) (cm(-2)·dyn(-1)·10(-6)). AR stiffness index was defined as (systolic blood pressure/diastolic blood pressure)/(systolic proximal ascending aortic diameter - diastolic proximal ascending aortic diameter)/diastolic proximal ascending aortic diameter. Analysis of variance was performed to evaluate differences among groups.

RESULTS

Left ventricular (LV) mass index did not significantly differ between the two groups of athletes but was lower in controls. ATS showed higher body surface area, sum of wall thickness (septum plus LV posterior wall), and circumferential end-systolic stress, while LV stroke volume and LV end-diastolic volume were greater in ATE. AR diameters at all levels and AR stiffness were significantly greater in ATS than in ATE and controls, while AR distensibility was significantly higher in ATE. However, AR dilatation was observed only in four male power athletes (1%). By multivariate analyses, in the overall population of athletes, age, LV stroke volume, endurance training, and duration of training were the only independent determinant of higher AR distensibility. On the other hand, age, circumferential end-systolic stress, strength training, and duration of training were independently associated with AR stiffness in ATS.

CONCLUSIONS

AR diameters and stiffness were significantly greater in strength-trained athletes, while aortic distensibility was higher in endurance athletes compared with age- and sex-matched healthy controls.

A new mouse model for marfan syndrome presents phenotypic variability associated with the genetic background and overall levels of Fbn1 expression

Marfan syndrome is an autosomal dominant disease of connective tissue caused by mutations in the fibrillin-1 encoding gene FBN1. Patients present cardiovascular, ocular and skeletal manifestations, and although being fully penetrant, MFS is characterized by a wide clinical variability both within and between families. Here we describe a new mouse model of MFS that recapitulates the clinical heterogeneity of the syndrome in humans. Heterozygotes for the mutant Fbn1 allele mgΔ^loxPneo, carrying the same internal deletion of exons 19–24 as the mgΔ mouse model, present defective microfibrillar deposition, emphysema, deterioration of aortic wall and kyphosis. However, the onset of a clinical phenotypes is earlier in the 129/Sv than in C57BL/6 background, indicating the existence of genetic modifiers of MFS between these two mouse strains. In addition, we characterized a wide clinical variability within the 129/Sv congenic heterozygotes, suggesting involvement of epigenetic factors in disease severity. Finally, we show a strong negative correlation between overall levels of Fbn1 expression and the severity of the phenotypes, corroborating the suggested protective role of normal fibrillin-1 in MFS pathogenesis, and supporting the development of therapies based on increasing Fbn1 expression.

Pulmonary dysfunction secondary to mandibular retrognathia in Marfan's syndrome

Referrals to pulmonary physicians for polysomnography to evaluate snoring or the possibility of sleep apnea syndrome often evolve into a multidisciplinary clinical problem. We present a young woman with two congenital abnormalities (Marfan's syndrome and retrognathism) which both may affect her decreased exercise tolerance, daytime hypersomnolence, and fatigue. Polysomnography and pulmonary exercise testing documented improvement in her upper airway diameter and exercise capacity. Her improved sleep pattern and her understanding of her exercise performance limitations afforded her a new outlook on life.

Diseases and disorders of muscle

Muscle may suffer from a number of diseases or disorders, some being fatal to humans and animals. Their management or treatment depends on correct diagnosis. Although no single method may be used to identify all diseases, recognition depends on the following diagnostic procedures: (1) history and clinical examination, (2) blood biochemistry, (3) electromyography, (4) muscle biopsy, (5) nuclear magnetic resonance, (6) measurement of muscle cross-sectional area, (7) tests of muscle function, (8) provocation tests, and (9) studies on protein turnover. One or all of these procedures may prove helpful in diagnosis, but even then identification of the disorder may not be possible. Nevertheless, each of these procedures can provide useful information. Among the most common diseases in muscle are the muscular dystrophies, in which the newly identified muscle protein dystrophin is either absent or present at less than normal amounts in both Duchenne and Becker's muscular dystrophy. Although the identification of dystrophin represents a major breakthrough, treatment has not progressed to the experimental stage. Other major diseases of muscle include the inflammatory myopathies and neuropathies. Atrophy and hypertrophy of muscle and the relationship of aging, exercise, and fatigue all add to our understanding of the behavior of normal and abnormal muscle. Some other interesting related diseases and disorders of muscle include myasthenia gravis, muscular dysgenesis, and myclonus. Disorders of energy metabolism include those caused by abnormal glycolysis (Von Gierke's, Pompe's, Cori-Forbes, Andersen's, McArdle's, Hers', and Tauri's diseases) and by the acquired diseases of glycolysis (disorders of mitochondrial oxidation). Still other diseases associated with abnormal energy metabolism include lipid-related disorders (carnitine and carnitine palmitoyl-transferase deficiencies) and myotonic syndromes (myotonia congenita, paramyotonia congenita, hypokalemic and hyperkalemic periodic paralysis, and malignant hyperexia). Diseases of the connective tissues discussed include those of nutritional origin (scurvy, lathyrism, starvation, and protein deficiency), the genetic diseases (dermatosparaxis, Ehlers-Danlos syndrome, osteogenesis imperfecta, Marfan syndrome, homocystinuria, alcaptonuria, epidermolysis bullosa, rheumatoid arthritis in humans, polyarthritis in swine, Aleutian disease of mink, and the several types of systemic lupus erythematosus) and the acquired diseases of connective tissues (abnormal calcification, systemic sclerosis, interstitial lung disease, hepatic fibrosis, and carcinomas of the connective tissues). Several of the diseases of connective tissues may prove to be useful models for determining the relationship of collagen to meat tenderness and its other physical properties. Several other promising models for studying the nutrition-related disorders and the quality-related characteristics of meat are also reviewed.

Endoscopic cure of a giant sacral meningocele associated with Marfan's syndrome: case report

An unusual anterior sacral meningocele associated with Marfan's syndrome, with demonstrated dural anomalies related to Marfan's syndrome is reported. Endoscopy enabled complete exploration of the meningocele, its morphological description, and ultimate cure. The meningocele resembled an hourglass made up of intrasacral and anterior sacral components. The communication of this bilobed malformation with the dural sac was so small that only the intrathecal injection of a colored solution allowed its localization. The closure of this communication was accomplished under endoscopic view by a single stitch. The postoperative course of the patient was characterized by immediate disappearance of the preoperative clinical signs. Computed tomographic scans demonstrated progressive complete collapse of the anterior sacral meningocele and partial resolution of the intrasacral component. Dural anomalies of Marfan's syndrome are described, and their relationship to the formation of the meningocele is discussed.

Schizophrenia and Marfan syndrome

Five index patients and three of their first-degree relatives were affected both by schizophrenia and Marfan syndrome. Since the association appears statistically significant, the possibility of linkage disequilibrium between adjacent genes or a cytogenetic abnormality causing both disorders is suggested. These hypotheses are testable and hold promise in attempting to map the 'schizophrenia susceptibility gene' by the candidate-gene approach.

Two-dimensional and Doppler echocardiographic and pathologic characteristics of the infantile Marfan syndrome

Since the clinical, 2-dimensional and Doppler echocardiographic and pathologic findings in infantile Marfan syndrome have not been documented in detail, a study of 9 such infants was performed. The previously reported 64 cases were reviewed and the salient findings in 22 additional cases were discussed. The age at diagnosis in our 9 cases ranged from birth to 12 months (mean 2.7 months). Mitral valve prolapse was demonstrated in all, with mitral regurgitation in 8. Tricuspid valve prolapse was present in 8, with tricuspid regurgitation in 6. Marked aortic root dilatation was present in all, and was progressive. The aortic root assumed a "clover leaf" appearance in the parasternal short-axis view. Aortic regurgitation was documented initially in 1 patient, and developed during follow-up in 4 of 7 infants. Dilation of the pulmonary arterial root and pulmonary regurgitation were found in 3 of 7 infants. Severe heart failure associated with mitral or tricuspid regurgitation was present in 7 of the 9 patients. Four infants died during the first year of life. The salient pathologic features were myxomatous thickening and redundancy of the mitral and tricuspid leaflets, marked elongation of chordae tendineae and prominent dilatation of the aortic and pulmonary roots. Histologically, the collagen and elastic fibers were severely disrupted, disarrayed and fragmented with increased interstitial ground substance. These data document that infantile Marfan syndrome is characterized by clinical and morphologic features that are distinctly different from the classic syndrome seen in adolescents and adults. The aforementioned findings should facilitate early clinical and echocardiographic diagnosis of infantile Marfan syndrome.

Case report 582: Lumbosacral meningocele and aortic aneurysm in Marfan syndrome

A patient with Marfan syndrome presented with enlargement of lumbosacral spinal canal with a bulky meningocele, and a fusiform aneurysm of the ascending aorta. In Marfan syndrome, the presence of a meningocele is extremely rare, but 60% of the patients develop cardio-vascular complications (a frequent cause of death). MRI is the imaging technique of choice for the diagnosis of meningocele and aortic aneurysm.

The tall athlete and Marfan syndrome. Need for clinical differentiation

A 14-year-old female athlete was referred because of her height, thinness, and long fingers. Investigation suggested that she did not have Marfan syndrome, but rather mitral valve prolapse. This case presentation demonstrates some of the difficult issues faced in sports medicine when dealing with athletes suspected of the Marfan syndrome or mitral valve prolapse.

Pleiotropy revisited: molecular explanations of a classic concept

As commonly used, pleiotropy refers to multiple effects on phenotype of a single mutant gene. The importance of this concept to medical genetics has waxed and waned since its formulation soon after the rediscovery of Mendel's laws. Initially, the view that all aspects of a phenotype, and hence all manifestations of a mendelian syndrome, derive from a single function (or dysfunction) of a mutant allele gained ascendancy. Support for the importance of pleiotropy gradually diminished, and reached a low point in the 1940s with the one gene-one enzyme hypothesis. Studies of mammals and humans with heritable disorders of connective tissue sustained the notion that "genuine" pleiotropy probably did not exist. However, the demise of the relevance of pleiotropy was premature. Detailed understanding of gene organization, expression, and mutation indicates several mechanisms, such as multifunctional proteins, alternative splicing of messenger RNA, and overlapping coding sequences, through which genuine pleiotropy likely occurs in normal development and function, in mendelian syndromes, and in conditions due to somatic mutation. Furthermore, a broad definition of pleiotropy is warranted to subsume syndromes caused by abnormal function of contiguous genes, such as through large deletions, mutation of regulatory elements that coordinate expression, or less clearly understood "position effects." Thus, the use of pleiotropy in the context of aneuploidy syndromes is not inappropriate.

Arterial hemodynamic indexes in Marfan's syndrome

Aortic impedance, wave reflection magnitude, and compliance were measured in patients with Marfan's syndrome during diagnostic cardiac catheterization. Impedance and wave reflections were calculated from standard Fourier series analysis of ascending aorta micromanometer pressure and electromagnetic flow records. Compliance was estimated by a method recently proposed that uses the area under the pressure-time curve assuming a two-element Windkessel model of the circulation. Measurements were made in the baseline state, during vasodilatation with nitroprusside, after beta-adrenergic receptor blockade with intravenous propranolol, and during vasodilatation after beta-blockade. Marfan's syndrome produces alterations from normal in some hemodynamic variables: during baseline conditions, the magnitude of wave reflection was higher than in normal patients. This was normalized by vasodilatation and further increased by beta-blockade. Despite the greatly dilated aortic root, the aortic characteristic impedance was in the normal range, suggesting increased aortic wall stiffness. The baseline total arterial compliance was greatly increased with nitroprusside and was reduced by beta-blockade. beta-Blockade did not decrease the maximum acceleration of blood into the ascending aorta. These are the first detailed measurements of hemodynamic indexes in this disease. The results suggest that acute beta-blockade is not necessarily beneficial in reducing hemodynamic loading on an already dilated aortic root.

Dural ectasia and the Marfan syndrome

The not-uncommon spinal abnormalities associated with Marfan's syndrome rarely undergird clinical problems, and neurological features accompanying such bone abnormalities are rare. In such unusual circumstances it is a widened vertebral canal that attracts attention: the substrate of such widening is dural ectasia with bone erosion, presumably due to hydraulic forces operating via the cerebrospinal fluid (CSF). When neural symptoms or findings do occur they may be related to stretching and traction mechanisms. This study of a symptomatic patient defined with reasonable clarity the abnormal anatomy, and some neurological symptom relief was achieved by attempting to alter the CSF dynamics. The relevant literature has been sampled to elucidate the condition.

Suspected Marfan Syndrome in a Female Basketball Player

A group of experts met to discuss a case from the University of California, San Diego, School of Medicine. This case conference is part of a series featuring a variety of sports medicine topics.

Marfan syndrome: exclusion of genetic linkage to three major collagen genes

The Marfan syndrome is an autosomal dominant connective tissue disorder with pleiotropic manifestations affecting skeletal, ocular and cardiovascular systems. Because the fibrillar collagens are major structural components of connective tissue, the hypothesis has long been set forth that the Marfan syndrome is a disorder of fibrillar collagen. We have investigated this hypothesis by performing linkage studies in 12 multiplex families with the Marfan syndrome, using restriction fragment length polymorphisms (RFLP's) associated with 3 genes encoding chains of fibrillar collagens. The data exclude linkage to all 3 candidate genes in 2 families and at least 1 of the candidates is excluded in 6 additional families. Each candidate was excluded in at least 3 families. In no case was strong evidence in favor of linkage of the Marfan syndrome to any of the 3 genes observed. These data speak against the hypothesis that mutations in one or more of these 3 fibrillar collagens cause the classic Marfan syndrome.

Exclusion of the alpha 2(I) and alpha 1(III) collagen genes as the mutant loci in a Marfan syndrome family

The inheritance of restriction fragment length polymorphisms for two fibrillar collagen genes (COL1A2 and COL3A1) has been studied in a large Marfan syndrome kindred. We are able to show discordant segregation between the Marfan syndrome and each of the two collagen gene markers.

Pulmonary function in the Marfan syndrome

To explore the causes of reported abnormalities in pulmonary function in persons with the Marfan syndrome, we analyzed retrospective anthropometric and pulmonary function tests in 79 patients. For ten subjects, there were matched, related control subjects who did not have a connective tissue disorder. Patients had lower values of FVC and TLC than the values expected for their standing heights (83 and 91 percent). However, when sitting height was used to calculate expected spirometric values, patients free of severe deformity of the thoracic cage did not have significant spirometric abnormalities (FVC 105 percent, FEV1 92 percent). However, patients with moderate-to-severe pectus excavatum or scoliosis (common features of the Marfan syndrome) had marked reductions in total lung capacity as well as in FVC and FEV1, suggesting a restrictive ventilatory defect. The abnormalities of pulmonary function often found in clinical laboratories can be explained in most cases by inappropriate use of standing height to calculate expected values, by thoracic cage deformity, or by both. We have found no evidence from standard tests of pulmonary function for a connective tissue defect of lung parenchyma that is of clinical importance in Marfan patients who lack chest wall deformity.

Aortic elastin abnormalities in osteogenesis imperfecta type II

Skin and aortic samples from two patients who died by lethal perinatal Osteogenesis Imperfecta (O.I.) were studied by optical and electron microscopy and compared with similar samples from two normal human fetuses and one newborn child. No significant abnormalities were observed in the dermis of O.I. patients apart from small differences in the diameter of reticular collagen fibrils. On the contrary, in the aortas of both patients collagen fibrils were significantly smaller than in the controls; moreover, elastin lamellae were deeply altered and consisted of roundish aggregates of elastin, massively permeated by cytochemically recognizable glycosaminoglycans. As identical features were described in experimental lathyrism by using inhibitors of the enzyme lysyl oxidase (Pasquali Ronchetti et al., 1984), the conclusion is reached that in the two cases of lethal perinatal O.I. examined, a severe lysyl oxidase deficiency could account for the observed ultrastructural abnormalities of elastin and that, besides defects of collagen type I, additional alterations of cellular metabolism might be responsible for the clinical heterogeneity of the disease.

Pneumothorax in the Marfan syndrome: prevalence and therapy

At least twenty-four reports of pneumothorax associated with the Marfan syndrome have appeared in the medical literature, but the frequency and optimal method of treatment remain unclear. We conducted a retrospective review of medical records from one genetics clinic and found that the frequency of spontaneous pneumothorax in patients older than 12 years with Marfan's syndrome was 4.4% (11 out of 249). Men were more commonly, but no more severely, affected than women. Seven patients had recurrent or bilateral pneumothorax. In 9 of the 11 patients, apical bullae were present and detectable on chest radiograph. Pneumothorax frequently recurred if not treated by resection of the offending bullae. We recommend that all adolescent and adult patients with the Marfan syndrome undergo chest radiography for ascertainment of the gross pathological condition of the lung. Definitive surgical treatment should be performed at the first occurrence of pneumothorax because of the high rate of recurrence after treatment with a chest tube, with or without pleurodesis.

Homozygosity for autosomal dominant Marfan syndrome

Marfan syndrome is an autosomal dominant condition with varying phenotypic manifestations. Affected persons are usually heterozygotes. A family is presented in which the gene for this syndrome is segregating in a large number of members. Two sibs suffered from unusually severe, identical, and fatal manifestations from birth, their parents having mild cardiovascular and somatic symptoms common in Marfan syndrome. Investigation of collagen biosynthesis in fibroblasts revealed no abnormalities in fibronectin and procollagen I and III synthesis and secretion or in the procollagen to collagen conversion. We suggest that these two sibs are examples of homozygosity for the Marfan syndrome gene, based on the large number of affected members, the absence of additional consanguinity, manifestation of the syndrome in both parents, and the severity of the disease in the two sibs.

Mitral valve dysfunction in the Marfan syndrome. Clinical and echocardiographic study of prevalence and natural history

Although mitral regurgitation and fibromyxomatous thickening of the mitral leaflets have long been recognized as such, mitral valve prolapse has only recently been added as one of the pleiotropic features of the Marfan syndrome. The prevalence, age of onset, and natural history of mitral valve dysfunction in this condition are uncertain. Therefore, all patients in one clinic who met strict diagnostic criteria for the Marfan syndrome and who had clinical and echocardiographic examinations before age 22 years were reviewed. Of the 166 patients (84 males, aged 11.9 +/- 0.6 years [mean +/- SEM]; and 82 females, 11.0 +/- 0.6 years), 52 percent had auscultatory and 68 percent had echocardiographic evidence of mitral valve dysfunction, generally mitral valve prolapse. Prevalence did not differ between the sexes. Follow-up in 115 patients averaged five examinations over a mean of four years; 17 percent were followed for more than six years. Criteria for progression of mitral valve dysfunction were: (1) on auscultation, the appearance of new systolic clicks or apical systolic murmurs, a mitral regurgitant murmur increased by two grades, or appearance of congestive heart failure not due to aortic regurgitation; and (2) on echocardiography, the new appearance of mitral valve prolapse or abnormally increased left atrial dimension. Nearly half the patients met at least one criterion and one quarter had both auscultatory and echocardiographic evidence of progressive mitral valve dysfunction. Twice as many females demonstrated worse mitral valve function with time. Eight of the 166 patients either died as a result of mitral valve dysfunction or required mitral valve replacement. Severe mitral regurgitation developed in an additional 15 patients. Rupture of chordae tendineae was uncommon. Antibiotic prophylaxis was routine, and no cases of bacterial endocarditis of the mitral valve occurred. These results suggest that mitral valve dysfunction is extremely common in young patients with Marfan syndrome and usually presents as mitral valve prolapse. Serious mitral regurgitation develops in one of every eight patients by the third decade. Thus, the prevalence and natural history of mitral valve prolapse in the Marfan syndrome appear distinct from mitral valve prolapse associated with other conditions, including idiopathic or familial mitral valve prolapse.

Desmosines in aneurysms of the ascending aorta (annulo-aortic ectasia)

Amino acid chromatography was used for determination of the elastin-specific amino acids desmosine and isodesmosine in acid hydrolyzates of intima-medial samples taken intraoperatively from aneurysms of human ascending aorta. Elastin concentration of the specimens was also estimated by hot alkali extraction followed by nitrogen determination of the extracted material and the insoluble residue. All patients studied had annulo-aortic ectasia i.e., dilatation of the aortic annulus and the ascending aorta. Two patients with the Marfan syndrome had low aortic elastin concentration determined by both methods. A third Marfan syndrome patient, youngest of the three, also had a slightly reduced concentration of elastin in the aorta. Aortic samples were studied from five patients who did not have the classical Marfan syndrome. Two patients of those five had decreased aortic elastin concentration. The change in elastin concentration was accompanied by high hydroxyproline/proline or hydroxylysine/lysine ratios which indicates that the proteins of the aneurysmatic aortic wall contained more collagen than the proteins of the control aortic wall. These findings point to a change in the structure or metabolism of elastin in the aortic wall in the Marfan syndrome and at least in some other patients with annulo-aortic ectasia.