Physicians' perspectives on the uncertainties and implications of chromosomal microarray testing of children and families

Chromosomal microarray analysis (CMA) has improved the diagnostic rate of genomic disorders in pediatric populations, but can produce uncertain and unexpected findings. This article explores clinicians' perspectives and identifies challenges in effectively interpreting results and communicating with families about CMA. Responses to an online survey were obtained from 40 clinicians who had ordered CMA. Content included practice characteristics and perceptions, and queries about a hypothetical case involving uncertain and incidental findings. Data were analyzed using nonparametric statistical tests. Clinicians' comfort levels differed significantly for explaining uncertain, abnormal, and normal CMA results, with lowest levels for uncertain results. Despite clinical guidelines recommending informed consent, many clinicians did not consider it pertinent to discuss the potential for CMA to reveal information concerning biological parentage or predisposition to late-onset disease, in a hypothetical case. Many non-genetics professionals ordering CMA did not feel equipped to interpret the results for patients, and articulated needs for education and access to genetics professionals. This exploratory study highlights key challenges in the practice of genomic medicine, and identifies needs for education, disseminated practice guidelines, and access to genetics professionals, especially when dealing with uncertain or unexpected findings.

Motivations and perceptions of early adopters of personalized genomics: perspectives from research participants

BACKGROUND/AIMS

To predict the potential public health impact of personal genomics, empirical research on public perceptions of these services is needed. In this study, 'early adopters' of personal genomics were surveyed to assess their motivations, perceptions and intentions.

METHODS

Participants were recruited from everyone who registered to attend an enrollment event for the Coriell Personalized Medicine Collaborative, a United States-based (Camden, N.J.) research study of the utility of personalized medicine, between March 31, 2009 and April 1, 2010 (n = 369). Participants completed an Internet-based survey about their motivations, awareness of personalized medicine, perceptions of study risks and benefits, and intentions to share results with health care providers.

RESULTS

Respondents were motivated to participate for their own curiosity and to find out their disease risk to improve their health. Fewer than 10% expressed deterministic perspectives about genetic risk, but 32% had misperceptions about the research study or personal genomic testing. Most respondents perceived the study to have health-related benefits. Nearly all (92%) intended to share their results with physicians, primarily to request specific medical recommendations.

CONCLUSION

Early adopters of personal genomics are prospectively enthusiastic about using genomic profiling information to improve their health, in close consultation with their physicians. This suggests that early users (i.e. through direct-to-consumer companies or research) may follow up with the health care system. Further research should address whether intentions to seek care match actual behaviors.

International guidelines for the diagnosis and management of hereditary haemorrhagic telangiectasia

BACKGROUND

HHT is an autosomal dominant disease with an estimated prevalence of at least 1/5000 which can frequently be complicated by the presence of clinically significant arteriovenous malformations in the brain, lung, gastrointestinal tract and liver. HHT is under-diagnosed and families may be unaware of the available screening and treatment, leading to unnecessary stroke and life-threatening hemorrhage in children and adults.

OBJECTIVE

The goal of this international HHT guidelines process was to develop evidence-informed consensus guidelines regarding the diagnosis of HHT and the prevention of HHT-related complications and treatment of symptomatic disease.

METHODS

The overall guidelines process was developed using the AGREE framework, using a systematic search strategy and literature retrieval with incorporation of expert evidence in a structured consensus process where published literature was lacking. The Guidelines Working Group included experts (clinical and genetic) from eleven countries, in all aspects of HHT, guidelines methodologists, health care workers, health care administrators, HHT clinic staff, medical trainees, patient advocacy representatives and patients with HHT. The Working Group determined clinically relevant questions during the pre-conference process. The literature search was conducted using the OVID MEDLINE database, from 1966 to October 2006. The Working Group subsequently convened at the Guidelines Conference to partake in a structured consensus process using the evidence tables generated from the systematic searches.

RESULTS

The outcome of the conference was the generation of 33 recommendations for the diagnosis and management of HHT, with at least 80% agreement amongst the expert panel for 30 of the 33 recommendations.

SMAD4 mutations found in unselected HHT patients

BACKGROUND

Hereditary haemorrhagic telangiectasia (HHT) is an autosomal dominant disease exhibiting multifocal vascular telangiectases and arteriovenous malformations. The majority of cases are caused by mutations in either the endoglin (ENG) or activin receptor-like kinase 1 (ALK1, ACVRL1) genes; both members of the transforming growth factor (TGF)-beta pathway. Mutations in SMAD4, another TGF-beta pathway member, are seen in patients with the combined syndrome of juvenile polyposis (JP) and HHT (JP-HHT).

METHODS

We sought to determine if HHT patients without any apparent history of JP, who were undergoing routine diagnostic testing, would have mutations in SMAD4. We tested 30 unrelated HHT patients, all of whom had been referred for DNA based testing for HHT and were found to be negative for mutations in ENG and ALK1.

RESULTS

Three of these people harboured mutations in SMAD4, a rate of 10% (3/30). The SMAD4 mutations were similar to those found in other patients with the JP-HHT syndrome.

CONCLUSIONS

The identification of SMAD4 mutations in HHT patients without prior diagnosis of JP has significant and immediate clinical implications, as these people are likely to be at risk of having JP-HHT with the associated increased risk of gastrointestinal cancer. We propose that routine DNA based testing for HHT should include SMAD4 for samples in which mutations in neither ENG nor ALK1 are identified. HHT patients with SMAD4 mutations should be screened for colonic and gastric polyps associated with JP.

Empowering primary care health professionals in medical genetics: how soon? How fast? How far?

Applications of genetics to the practices of medicine and public health are important today and will only become more compelling as our understanding of the human genome evolves. Because of a perceived lack of medical genetics professionals, it is generally believed that primary health care providers (PCPs) will need to assume prominent roles in delivering clinical genetics services. However, a number of studies indicate that most PCPs are neither well enough educated in genetics nor interested enough in becoming so to effectively contribute. Those who advocate empowering PCPs must be aware of potential problems with any approach thus far suggested for achieving this goal. Moreover, any analysis of this model must consider the potential ramifications for medical genetics professionals, patients, and families. In this article, we explore some of the unique features of the culture of medical genetics services and service providers. We discuss how important this culture is to clinical outcomes and the likelihood that its positive attributes would be preserved in a PCP model of medical genetics service delivery.

Age-associated changes in regional aortic pulse wave velocity

OBJECTIVES

This study was designed to determine noninvasively the age-associated changes in regional mechanical properties in normals using phase-contrast magnetic resonance imaging (PCMRI).

BACKGROUND

It has been well documented that there is a progressive increase in aortic pulse wave velocity (PWV) with age. Previously, PWV has been measured at a single aortic location, or has compared arterial waves between carotid and femoral points to determine PWV.

METHODS

Applanation tonometry (TONO) and in-plane PCMR was performed in 24 volunteers (12 men) ranging in age from 21 to 72 years old. The PCMRI PWV was measured in three aortic segments. As validation, TONO was performed to determine PWV between the carotid and femoral artery.

RESULTS

When PCMRI PWV was averaged over the three locations, it was not different from TONO (7.9 +/- 2.3 vs. 7.6 +/- 2.4 m/s, respectively). When the volunteers were divided into groups of < 55 and > or =55 years old, the younger group showed similar PWV at each aortic location. However, the older group displayed significantly increased PWV in the region spanning the ascending and proximal descending aorta compared with the mid-thoracic or abdominal segments (10.6 +/- 2.5 m/s, 9.2 +/- 2.8 m/s, and 7.1 +/- 1.7 m/s, respectively, p < 0.001, analysis of variance).

CONCLUSIONS

In-plane PCMRI permits determination of PWV in multiple aortic locations in a single acquisition. Progressive fragmentation of elastic fibers and alterations in the regulation of vascular tone may result in an age-related, regional increase in PWV primarily affecting the proximal aorta.

Disorders of vascular fragility: implications for active patients

Circulatory vessels are subject to diverse pathologic processes that depend on the properties of the vessels. Vascular problems such as dilatation, dissection, and rupture can occur as a result of many disorders. Conditions that affect vessels include inherited disorders such as Marfan syndrome and the Ehlers-Danlos syndromes and poorly understood congenital disorders such as arteriovenous malformations and capillary fragility. Depending on which condition patients have, they must be given proper counseling about activity and options for management. For some patients, strenuous exercise, pregnancy, and competitive sports are prohibited, but for others with milder disorders, participation in selected sports is permitted.

Clinical responses to bone marrow transplantation in children with severe osteogenesis imperfecta

Preclinical models have shown that transplantation of marrow mesenchymal cells has the potential to correct inherited disorders of bone, cartilage, and muscle. The report describes clinical responses of the first children to undergo allogeneic bone marrow transplantation (BMT) for severe osteogenesis imperfecta (OI), a genetic disorder characterized by defective type I collagen, osteopenia, bone fragility, severe bony deformities, and growth retardation. Five children with severe OI were enrolled in a study of BMT from human leukocyte antigen (HLA)-compatible sibling donors. Linear growth, bone mineralization, and fracture rate were taken as measures of treatment response. The 3 children with documented donor osteoblast engraftment had a median 7.5-cm increase in body length (range, 6.5-8.0 cm) 6 months after transplantation compared with 1.25 cm (range, 1.0-1.5 cm) for age-matched control patients. These patients gained 21.0 to 65.3 g total body bone mineral content by 3 months after treatment or 45% to 77% of their baseline values. With extended follow-up, the patients' growth rates either slowed or reached a plateau phase. Bone mineral content continued to increase at a rate similar to that for weight-matched healthy children, even as growth rates declined. These results suggest that BMT from HLA-compatible donors may benefit children with severe OI. Further studies are needed to determine the full potential of this strategy.

A deficiency of cysteine impairs fibrillin-1 deposition: implications for the pathogenesis of cystathionine beta-synthase deficiency

Cystathionine beta-synthase (CBS) deficiency is an inborn error of amino acid metabolism that has pleiotropic manifestations and is commonly called "homocystinuria." The features include skeletal, ocular, and vascular defects, some of which are reminiscent of those found in Marfan syndrome (MFS). Because of the spectrum of clinical effects, the pathogenesis of homocystinuria has long been thought to involve the extracellular matrix (ECM), and the condition has been classified as a heritable disorder of connective tissue. Because of the superficial similarities with MFS, we and others (Pyeritz, in McKusicks Heritable Disorders of Connective Tissue, St. Louis, Mosby-Year Book Inc., 5th ed., pp 137-178, 1993; Pyeritz, in Principles and Practice of Medical Genetics, New York, Churchill Livingstone, 3rd ed., pp 1027-1066, 1997; Mudd, Levy, and Skovby, in The Metabolic and Molecular Bases of Inherited Disease, New York, McGraw-Hill Publishing Co., 7th ed., pp 1279-1327, 1995) have speculated how CBS deficiency might affect fibrillin-1, the protein altered in MFS. For example, the altered plasma concentrations of homocysteine and/or cysteine in patients with CBS deficiency may hinder fibrillin-1 synthesis, deposition, or both. When arterial smooth muscle cells were cultured under conditions of cysteine deficiency, fibrillin-1 deposition into the ECM was greatly diminished as revealed by immunocytochemistry. Excessive homocysteine, in contrast, had little, if any, effect on fibrillin-1 deposition. When cysteine concentrations were returned to normal, the smooth muscle cells began to accumulate a matrix rich in fibrillin-1. Type I collagen, the major matrix component synthesized by these smooth muscle cells, was not reduced by low cysteine concentrations nor high homocysteine concentrations. These results demonstrate that a deficiency of cysteine and subsequent inhibition of fibrillin-1 accumulation in CBS deficient patients may be at least partly responsible for their phenotype, and suggest that maintenance of normal plasma cyst(e)ine levels may be an important therapeutic goal.

The Marfan syndrome

The Marfan syndrome (MFS), initially described just over 100 years ago, was among the first conditions classified as a heritable disorder of connective tissue. MFS lies at one end of a phenotypic continuum, with people in the general population who have one or another of the features of MFS at the other end, and those with a variety of other conditions in between. Diagnosis of MFS and these other conditions remains based on clinical features. Mutations in FBN1, the gene that encodes fibrillin-1, are responsible for MFS and (in a few patients) other disorders in the continuum. In addition to skeletal, ocular, and cardiovascular features, patients with MFS have involvement of the skin, integument, lungs, and muscle tissue. Over the past 30 years, evolution of aggressive medical and surgical management of the cardiovascular problems, especially mitral valve prolapse, aortic dilatation, and aortic dissection, has resulted in considerable improvement in life expectancy.

Atlantoaxial rotatory subluxation in patients with Marfan syndrome. A report of three cases

STUDY DESIGN

This is a retrospective case series of three patients, ages 9 1/2, 13, and 20 years old, with Marfan syndrome treated for atlantoaxial rotatory subluxation. In the first two cases, acute torticollis was noted postoperatively, following pectus excavatum repair. The diagnosis was made in the third patient after she presented to the emergency room with a week-long history of unresolved neck pain following minor trauma.

OBJECTIVE

To report and discuss the courses and clinical sequelae of atlantoaxial subluxation in patients with Marfan syndrome.

SUMMARY OF BACKGROUND DATA

Radiographic analysis of patients with Marfan syndrome has shown that increased atlantoaxial translation, larger odontoid height, and basilar impression are more prevalent in this population compared to age-matched controls. Despite these findings, there are sparse data on injuries secondary to cervical spine instability or abnormalities in this population. To the authors' best knowledge, no report of atlantoaxial rotatory subluxation in patients with Marfan syndrome exists in the literature.

METHODS

Case records of rotatory instability of the atlanto-axial level were reviewed and are presented in the following report.

RESULTS

The first two patients described in this report were noted to have "cock robin" posturing of their necks following pectus excavatum repairs. The first patient's subluxation was partially reduced with halo traction, and he subsequently underwent posterior spinal fusion of C1-C2 with internal fixation. The patient was well aligned postoperatively, and had no neurologic deficits. The second patient's subluxation reduced after 20 days of halter and traction; he was immobilized in a collar following discharge and reduction was maintained. The third patient's subluxation failed to reduce with halo traction; further imaging studies revealed odontoid prominence in the foramen magnum. She underwent posterior spinal fusion, occiput to C3, with satisfactory result.

CONCLUSIONS

The cervical bony and ligamentous abnormalities seen in patients with Marfan syndrome may slightly increase their risk for atlantoaxial rotatory instability. Special attention to intubation and positioning, both intraoperatively and postoperatively, may be necessary in patients with Marfan syndrome. Additionally, rotatory subluxation should be included in the differential diagnosis for Marfan patients with neck pain after injury.

Comparison of heteroduplex analysis, direct sequencing, and enzyme mismatch cleavage for detecting mutations in a large gene, FBN1

Analysis of large genes for mutations of clinical relevance is complicated by intragenic heterogeneity, sensitivity, and cost of the methods available, and in the case of many conditions, specificity of the genetic alterations detected. We examined the FBN1 gene for mutations in people who had Marfan syndrome using three methods: single-chain polymorphism analysis (SSCP) with heteroduplex (HA) analysis, enzyme-mediated cleavage (EMC) of heteroduplexes, and direct sequencing. We also used these methods to search for mutations in the P53 gene in patients with hepatocellular carcinoma. The results showed that EMC was most efficient for detecting mutations. However, the cost favored SSCP with heteroduplex analysis, provided conditions did not need to be optimized to detect a mutation. Until more cost-effective and sensitive methods are developed to detect unknown mutations in large genes, diagnosis of many genetic disorders will depend on the willingness of an investigator who is studying a particular disorder to perform clinical molecular testing and have the laboratory accredited.

Splice-site mutations in atherosclerosis candidate genes: relating individual information to phenotype

BACKGROUND

Nucleotide variants in several genes for lipid and methionine metabolism influence the risk of premature atherosclerosis. Ten percent of single nucleotide substitutions in these genes involve mRNA splice sites. The effects of some of these changes on splicing and on phenotypic severity are not inherently obvious.

METHODS AND RESULTS

Using an information theory-based model, we measured the individual information content (R(i), in bits) of splice sites adjacent to 289 mutations (including 31 splice-site mutations) in the atherosclerosis candidate genes APOAII, APOB, APOCII, APOE, CBS, CETP, LCAT, LIPA, LDLR, and LPL. The predictions of information analysis were then corroborated by published mRNA analyses. The R(i) values of mutant sites were consistent with either complete (n=17) or partial (n=8) inactivation of these sites. Seven mutations were predicted to activate cryptic splice sites. Predicted inactive mutant sites were associated with either "average" or "severe" dyslipidemia and commensurate reductions in protein levels or activity, whereas mutations expected to exhibit residual splicing had average or "mild" effects on lipid and protein expression.

CONCLUSIONS

Information analysis of splice-junction variants in atherosclerosis candidate genes distinguishes inactive from leaky splice sites and identifies activated cryptic sites. Predicted changes in splicing were related to phenotypic severity.

Issues in implementing prenatal screening for cystic fibrosis: results of a working conference

PURPOSE

To summarize a conference convened to examine how cystic fibrosis screening might appropriately be introduced into routine prenatal practice.

METHODS

Participants included experts from various relevant disciplines. Systematic reviews and data from individual trials were presented; issues were identified and discussed.

RESULTS

Judged by published criteria, prenatal cystic fibrosis screening is suitable for introduction. Screening can be performed cost-effectively by identifying racial/ethnic groups at sufficient risk and then using either of two models for delivering laboratory services. Validated educational materials exist. Ethical issues are not unique.

CONCLUSIONS

Once adequate facilities for patient and provider education, testing, counseling, quality control, and monitoring are in place, individual programs can begin prenatal screening for cystic fibrosis.

Replacement of the aortic root in patients with Marfan's syndrome

BACKGROUND

Replacement of the aortic root with a prosthetic graft and valve in patients with Marfan's syndrome may prevent premature death from rupture of an aneurysm or aortic dissection. We reviewed the results of this surgical procedure at 10 experienced surgical centers.

METHODS

A total of 675 patients with Marfan's syndrome underwent replacement of the aortic root. Survival and morbidity-free survival curves were calculated, and risk factors were determined from a multivariable regression analysis.

RESULTS

The 30-day mortality rate was 1.5 percent among the 455 patients who underwent elective repair, 2.6 percent among the 117 patients who underwent urgent repair (within 7 days after a surgical consultation), and 11.7 percent among the 103 patients who underwent emergency repair (within 24 hours after a surgical consultation). Of the 675 patients, 202 (30 percent) had aortic dissection involving the ascending aorta. Forty-six percent of the 158 adult patients with aortic dissection and a documented aortic diameter had an aneurysm with a diameter of 6.5 cm or less. There were 114 late deaths (more than 30 days after surgery); dissection or rupture of the residual aorta (22 patients) and arrhythmia (21 patients) were the principal causes of late death. The risk of death was greatest within the first 60 days after surgery, then rapidly decreased to a constant level by the end of the first year.

CONCLUSIONS

Elective aortic-root replacement has a low operative mortality. In contrast, emergency repair, usually for acute aortic dissection, is associated with a much higher early mortality. Because nearly half the adult patients with aortic dissection had an aortic-root diameter of 6.5 cm or less at the time of operation, it may be prudent to undertake prophylactic repair of aortic aneurysms in patients with Marfan's syndrome when the diameter of the aorta is well below that size.

Transplantability and therapeutic effects of bone marrow-derived mesenchymal cells in children with osteogenesis imperfecta

In principle, transplantation of mesenchymal progenitor cells would attenuate or possibly correct genetic disorders of bone, cartilage and muscle, but clinical support for this concept is lacking. Here we describe the initial results of allogeneic bone marrow transplantation in three children with osteogenesis imperfecta, a genetic disorder in which osteoblasts produce defective type I collagen, leading to osteopenia, multiple fractures, severe bony deformities and considerably shortened stature. Three months after osteoblast engraftment (1.5-2.0% donor cells), representative specimens of trabecular bone showed histologic changes indicative of new dense bone formation. All patients had increases in total body bone mineral content ranging from 21 to 29 grams (median, 28), compared with predicted values of 0 to 4 grams (median, 0) for healthy children with similar changes in weight. These improvements were associated with increases in growth velocity and reduced frequencies of bone fracture. Thus, allogeneic bone marrow transplantation can lead to engraftment of functional mesenchymal progenitor cells, indicating the feasibility of this strategy in the treatment of osteogenesis imperfecta and perhaps other mesenchymal stem cell disorders as well.

The diagnostic evaluation and multidisciplinary management of neurofibromatosis 1 and neurofibromatosis 2

OBJECTIVE

Neurofibromatosis 1 and neurofibromatosis 2 are autosomal dominant genetic disorders in which affected individuals develop both benign and malignant tumors at an increased frequency. Since the original National Institutes of Health Consensus Development Conference in 1987, there has been significant progress toward a more complete understanding of the molecular bases for neurofibromatosis 1 and neurofibromatosis 2. Our objective was to determine the diagnostic criteria for neurofibromatosis 1 and neurofibromatosis 2, recommendations for the care of patients and their families at diagnosis and during routine follow-up, and the role of DNA diagnostic testing in the evaluation of these disorders.

DATA SOURCES

Published reports from 1966 through 1996 obtained by MEDLINE search and studies presented at national and international meetings.

STUDY SELECTION

All studies were reviewed and analyzed by consensus from multiple authors.

DATA EXTRACTION

Peer-reviewed published data were critically evaluated by independent extraction by multiple authors.

DATA SYNTHESIS

The main results of the review were qualitative and were reviewed by neurofibromatosis clinical directors worldwide through an Internet Web site.

CONCLUSIONS

On the basis of the information presented in this review, we propose a comprehensive approach to the diagnosis and treatment of individuals with neurofibromatosis 1 and neurofibromatosis 2.

The diagnostic evaluation and multidisciplinary management of neurofibromatosis 1 and neurofibromatosis 2

OBJECTIVE

Neurofibromatosis 1 and neurofibromatosis 2 are autosomal dominant genetic disorders in which affected individuals develop both benign and malignant tumors at an increased frequency. Since the original National Institutes of Health Consensus Development Conference in 1987, there has been significant progress toward a more complete understanding of the molecular bases for neurofibromatosis 1 and neurofibromatosis 2. Our objective was to determine the diagnostic criteria for neurofibromatosis 1 and neurofibromatosis 2, recommendations for the care of patients and their families at diagnosis and during routine follow-up, and the role of DNA diagnostic testing in the evaluation of these disorders.

DATA SOURCES

Published reports from 1966 through 1996 obtained by MEDLINE search and studies presented at national and international meetings.

STUDY SELECTION

All studies were reviewed and analyzed by consensus from multiple authors.

DATA EXTRACTION

Peer-reviewed published data were critically evaluated by independent extraction by multiple authors.

DATA SYNTHESIS

The main results of the review were qualitative and were reviewed by neurofibromatosis clinical directors worldwide through an Internet Web site.

CONCLUSIONS

On the basis of the information presented in this review, we propose a comprehensive approach to the diagnosis and treatment of individuals with neurofibromatosis 1 and neurofibromatosis 2.

The cervical spine in Marfan syndrome

STUDY DESIGN

Prospective radiographic and clinical analysis of a consecutive unselected population of persons with Marfan Syndrome.

OBJECTIVES

To determine cervical spine abnormalities present in the Marfan population compared with that seen in the general population.

SUMMARY OF BACKGROUND DATA

In the treatment of a large population of patients with Marfan Syndrome, three serious cervical spine disorders were noted. To the authors' knowledge, no report of cervical abnormalities in patients with Marfan Syndrome exists in the literature. Therefore, the cervical spine in these patients was studied in a systematic fashion.

METHODS

An unselected group of 104 consecutive patients with Marfan Syndrome seen at a medical genetics follow-up examination underwent lateral neutral and flexion-extension cervical spine radiographs. Parameters of alignment, size, and stability were measured. Patients with Marfan Syndrome aged 35-45 years and matched controls were given a pain questionnaire to complete.

RESULTS

The prevalence of focal kyphosis was 16%. A large number of patients with Marfan Syndrome (54%) had increased atlantoaxial translation. The preadolescent Marfan population has a greater range of motion than either the adolescent or adult populations. The Marfan population has an increased radiographic prevalence of basilar impression (36%), and the odontoid height (3.69 +/- 0.53 cm) was larger than reported norms (2.34 +/- 0.22 cm). Cervical stenosis was rare, with 3% having a critical Torg ratio at C3 and 2% having a critical Torg ratio at C6. Neck pain frequency did not differ significantly from that of age-matched controls.

CONCLUSION

Based on the increased prevalence of several cervical bony and ligamentous abnormalities, patients with Marfan Syndrome were recommended to avoid sports with risks of high-impact loading of the cervical spine. Given the rarity of actual neurologic injuries in the Marfan population, however, radiographs for all patients with Marfan Syndrome undergoing general anesthesia is not recommended.

Infantile scoliosis in Marfan syndrome

STUDY DESIGN

A retrospective review of clinical data was conducted.

OBJECTIVES

To determine the characteristics of infantile scoliosis in Marfan syndrome and the response to treatment of patients with this condition.

SUMMARY OF BACKGROUND DATA

No previous study has reported the features of this condition nor the effect of treatment on patients with this syndrome.

METHODS

The data on all patients seen at one institution who had Marfan syndrome and scoliosis by age three were reviewed. Fourteen of the 600 patients from the group examined who had Marfan syndrome fit the above criteria. Skeletal and general features were studied.

RESULTS

Thirteen of the 14 patients had no family history of Marfan syndrome, a finding which does not fit the usual autosomal dominant inheritance pattern. All 14 patients had exaggeration of the Marfan. All but one patient had cardiac valvular insufficiency that required repair by age 11. Thirteen patients had thoracic aortic aneurysm, 10 had lens dislocation, and eight had sternal deformity. Three patients had hip dislocations, two had pyloric stenosis, and two had dural ectasia. Motor delay was evidenced by onset of walking past 18 months in nine patients; three of these patients were never able to walk independently. One patient each died at ages 1, 3, 4, and 8 years; all others have survived to present (mean age, 13 years). The mean curve of the patients' spines at presentation was 38 degrees. Eleven curves were double major, two were thoracolumbar, and one was double thoracic. Brace wear did not halt curve progression in any of the nine patients for whom it was used. Instrumentation without fusion was used in three patients for a mean of 3 years, with best results in one nonkyphotic curve. Nine patients underwent instrumented fusion at a mean age of 6.6 years (range, 3-13 years). Mean curve correction was 51% (from 72 degrees to 34 degrees). Final mean curve was 54 degrees for a mean correction of 20% at the 5-year (average, 5.4 years) follow-up examination. Acute complications occurred in three patients, and five patients needed a second surgery for late complications. Causes for curve increase after surgery included growth and loss of fixation.

CONCLUSIONS

In this most severe form of Marfan syndrome, bracing has a limited role and is only to be used if the curve is less than 40 degrees. Surgery should not be performed on a patient younger than four years of age because many patients with large curves before this age will succumb spontaneously to cardiac complications. Instrumentation without fusion should be considered only for patients with no significant kyphosis. Results of fusion are better for patients who are older than five years of age.

Fine mapping of the nail-patella syndrome locus at 9q34

Nail-patella syndrome (NPS), or onychoosteodysplasia, is an autosomal dominant, pleiotropic disorder characterized by nail dysplasia, absent or hypoplastic patellae, iliac horns, and nephropathy. Previous studies have demonstrated linkage of the nail-patella locus to the ABO and adenylate kinase loci on human chromosome 9q34. As a first step toward isolating the NPS gene, we present linkage analysis with 13 polymorphic markers in five families with a total of 69 affected persons. Two-point linkage analysis with the program MLINK showed tight linkage of NPS and the anonymous markers D9S112 (LOD = 27.0; theta = .00) and D9S315 (LOD = 22.0; theta = .00). Informative recombination events place the NPS locus within a 1-2-cM interval between D9S60 and the adenylate kinase gene (AK1).

The gene for the Ellis-van Creveld syndrome is located on chromosome 4p16

Ellis-van Creveld syndrome (EVC) is an autosomal recessive disorder characterized by disproportionate dwarfism, polydactyly, and congenital heart disease. This rare disorder is found with increased frequency among the Old Order Amish community in Lancaster County, Pennsylvania. We have used linkage analysis to localize the gene responsible for the EVC phenotype in nine interrelated Amish pedigrees and three unrelated families from Mexico, Ecuador, and Brazil. We now report the linkage for the Ellis-van Creveld syndrome gene to markers on the distal short arm of human chromosome 4, with Zmax = 6.91 at theta = 0.02 for marker HOX7, in a region proximal to the FGFR3 gene responsible for the achondroplasia phenotype.

Revised diagnostic criteria for the Marfan syndrome

In 1986, the diagnosis of the Marfan syndrome was codified on the basis of clinical criteria in the Berlin nosology [Beighton et al., 1988]. Over time, weaknesses have emerged in these criteria, a problem accentuated by the advent of molecular testing. In this paper, we propose a revision of diagnostic criteria for Marfan syndrome and related conditions. Most notable are: more stringent requirements for diagnosis of the Marfan syndrome in relatives of an unequivocally affected individual; skeletal involvement as a major criterion if at least 4 of 8 typical skeletal manifestations are present; potential contribution of molecular analysis to the diagnosis of Marfan syndrome; and delineation of initial criteria for diagnosis of other heritable conditions with partially overlapping phenotypes.

The Marfan syndrome and the cardiovascular surgeon

The authors present the current status of surgery for the cardiovascular manifestations of the Marfan syndrome. In addition, a brief review of current Marfan genetic research is presented. Data on all Marfan patients undergoing aortic root replacement at the Johns Hopkins Hospital (September 1976-June 1995) were analyzed. Survival and event-free curves were calculated and risk factors for early and late death were determined by univariate and multivariate analysis. Two hundred twelve Marfan patients underwent aortic root replacement using composite graft (202), homograft (8) or valve-sparing procedures (2). One hundred eighty-five patients underwent elective repair with no 30-day mortality. Twenty-seven patients underwent urgent surgery, primarily for acute dissection; two patients with aortic rupture died in the operating room. Actuarial survival of the 212 patients was 88% at 5 years, 78% at 10 years and 71% at 14 years. By multivariate analysis, only poor NYHA class, male gender and urgent surgery emerged as significant independent predictors of early or late mortality. Histologic examination of excised Marfan aortic leaflets by immunofluorescent staining for fibrillin showed fragmentation of elastin-associated microfibrils. These studies suggest cautious use of valve-sparing procedures in Marfan patients. Over the last 5 years significant progress has been made in identifying mutant genes that code for defective fibrillin microfibrils in Marfan patients. Attempts are underway to develop animal models of Marfan disease for study of possible gene therapy. Aortic root replacement can be performed in Marfan patients with operative risk under 5%. Long-term results are gratifying. At present, valve-sparing procedures should be used cautiously in Marfan patients because of fibrillin abnormalities in the preserved aortic valve leaflets.

A prospective longitudinal evaluation of pregnancy in the Marfan syndrome

OBJECTIVE

We undertook a prospective evaluation of the outcomes of pregnancy, both maternal and fetal, and the long-term impact of pregnancy on Marfan syndrome in a series of consecutive, unselected patients.

STUDY DESIGN

Forty-five pregnancies in 21 Marfan syndrome patients were prospectively observed in one institution between 1983 and 1992. During pregnancy, patients were monitored with serial echocardiograms and close attention to symptoms. Maternal and fetal outcomes were monitored with serial echocardiographic data were analyzed by least-squares regression. Eighteen of the patients were followed up for 15 months to 13 years after the completion of their last pregnancy for investigation of the long-term impact of pregnancy on the cardiovascular manifestations of Marfan syndrome.

RESULTS

Aortic dissection occurred in two patients, both with increased risk for dissection established before pregnancy. The incidence of obstetric complications otherwise did not exceed that in the general population. Echocardiographic data demonstrated little to no change in aortic root diameter throughout pregnancy in most patients. Long-term follow-up showed no apparent worsening of cardiovascular status attributable to pregnancy in comparison with a group of 18 women with Marfan syndrome who were of similar age, had a similar degree of disease severity, and underwent no pregnancies.

CONCLUSIONS

Patients with Marfan syndrome in whom cardiovascular involvement is minor and aortic root diameter is < 40 mm usually tolerate pregnancy well, with favorable maternal and fetal outcomes, and without subsequent evidence of aggravated aortic root dilatation over time.

Interstitial deletion of the long arm of chromosome 6 associated with unusual limb anomalies: report of two new patients and review of the literature

We report on unusual manifestations in 2 unrelated children with interstitial deletion of 6q, with nearly identical breakpoints of 6q16.2q23.1 and 6q16.3q22.3. Major findings include growth retardation, profound developmental delay, microcephaly, facial anomalies, sparse hair, congenital heart defects, and striking hand malformations. Discordant anomalies were duodenal atresia and hypoplastic genitalia in 1 child. Split-hand defect, polydactyly, gastrointestinal anomalies, and ectodermal dysplasia have not been described previously in children with 6q deletion. The presence of hand malformations in 2 children with similar deletion breakpoints strongly suggests that this is a candidate region for one or more genes involved in limb development. Comparison of the clinical findings of other patients with 6q2 deletion suggests a recognizable phenotype.

Mutations in the human gene for fibrillin-1 (FBN1) in the Marfan syndrome and related disorders

The extracellular microfibril, 10-14 nm in diameter, performs a number of functions, including serving as the scaffolding for deposition of tropoelastin to form elastic fibers. A variety of proteins compose the structure of microfibrils, the most prominent of which are the two fibrillins. Fibrillin-1 is encoded by FBN1 on human chromosome 15q21 and fibrillin-2 is encoded by FBN2 on 5q23. Each fibrillin monomer contains a large number of epidermal growth factor-like motifs, most capable of binding calcium ions, and a few motifs resembling the binding protein for transforming growth factor beta. In vitro polymerization of fibrillin monomers produces 'beads on a string' structures that look on electron microscopy much like microfibrils purified from the extracellular matrices of a variety of tissues. Mutations in FBN1 produce Marfan syndrome, a pleiotropic autosomal dominant connective tissue disorder with prominent manifestations in the skeleton, eye and cardiovascular system. A number of conditions related to Marfan syndrome are also due to FBN1 mutations. Contractural arachnodactyly is due to mutations in FBN2. In this paper we review the published mutations in these genes, preliminary results of genotype-phenotype correlations, and speculations regarding molecular pathogenesis.

Fifteen novel FBN1 mutations causing Marfan syndrome detected by heteroduplex analysis of genomic amplicons

Mutations in the gene encoding fibrillin-1 (FBN1), a component of the extracellular microfibril, cause the Marfan syndrome (MFS). This statement is supported by the observations that the classic Marfan phenotype cosegregates with intragenic and/or flanking marker alleles in all families tested and that a significant number of FBN1 mutations have been identified in affected individuals. We have now devised a method to screen the entire coding sequence and flanking splice junctions of FBN1. On completion for a panel of nine probands with classic MFS, six new mutations were identified that accounted for disease in seven (78%) of nine patients. Nine additional new mutations have been characterized in the early stages of a larger screening project. These 15 mutations were equally distributed throughout the gene and, with one exception, were specific to single families. One-third of mutations created premature termination codons, and 6 of 15 substituted residues with putative significance for calcium binding to epidermal growth factor (EGF)-like domains. Mutations causing severe and rapidly progressive disease that presents in the neonatal period can occur in a larger region of the gene than previously demonstrated, and the nature of the mutation is as important a determinant as its location, in predisposing to this phenotype.

The thoracolumbar spine in Marfan syndrome

We analyzed the prevalence, inheritance, progression, and functional implications of spinal deformity in Marfan syndrome using four different groups of patients. We studied 113 patients who had Marfan syndrome, eighty-two of whom were skeletally immature, in order to characterize the alignment and function of the spine. The patients were selected from a clinic that provides total care with no bias toward the presence of orthopaedic conditions. Scoliosis was identified in fifty-two of the eighty-two patients, and the prevalences for the sexes were equal. The thoracic portion of the curve was convex to the right in all but two patients. The mean kyphosis was greater than that in the general population. Five distinct sagittal profiles were identified on the basis of whether the thoracic kyphosis was within, greater than, or less than normal limits and whether the transition between the kyphosis and lordosis occurred at or caudad to the normal level or whether the curves were reversed. Spondylolisthesis was present in five patients (6 per cent), with a mean slip of 30 per cent. Fourteen pedigrees were studied in depth. There was no familial pattern of the scoliosis. A separate group of fifty-six patients with scoliosis, for whom serial follow-up radiographs were available, was studied for progression. Patients who had a curve of more than 30 degrees had mild progression, and those who had a curve of more than 50 degrees had marked progression (mean, 3 +/- 4 degrees per year). Pain and function of the back were studied in thirty patients who were thirty-five to forty-five years old; these patients were found to be more impaired than matched controls. The presence of scoliosis was associated with pain in the region of the curve in these patients.

Aortic root replacement. Risk factor analysis of a seventeen-year experience with 270 patients

Between September 1976 and September 1993, 270 patients underwent aortic root replacement at our institution. Two hundred fifty-two patients underwent a Bentall composite graft repair and 18 patients received a cryopreserved homograft aortic root. One hundred eighty-seven patients had a Marfan aneurysm of the ascending aorta (41 with dissection) and 53 patients had an aneurysm resulting from nonspecific medial degeneration (17 with dissection). These 240 patients were considered to have annuloaortic ectasia. Thirty patients were operated on for miscellaneous lesions of the aortic root. Thirty-day mortality for the overall series of 270 patients was 4.8% (13/270). There was no 30-day mortality among 182 patients undergoing elective root replacement for annuloaortic ectasia without dissection. Thirty-six of the 270 patients having root replacement also had mitral valve operations. There was no hospital mortality for aortic root replacement in these 36 patients, but there were seven late deaths. Twenty-two patients received a cryopreserved homograft aortic root; 18 of these were primary root replacements and four were repeat root replacements for late endocarditis. One early death and two late deaths occurred in this group. Actuarial survival for the overall group of 270 patients was 73% at 10 years. In a multivariate analysis, only poor New Year Heart Association class (III and IV), non-Marfan status, preoperative dissection, and male gender emerged as significant predictors of early or late death. Endocarditis was the most common late complication (14 of 256 hospital survivors) and was optimally treated by root replacement with a cryopreserved aortic homograft. Late problems with the part of the aorta not operated on occur with moderate frequency; careful follow-up of the distal aorta is critical to long-term survival.

The Marfan syndrome: joint and skin manifestations are prevalent and correlated

The objective of the study was to ascertain the occurrence and inter-relationships of locomotor symptoms, joint hypermobility and skin involvement in patients with the Marfan syndrome. A single clinical evaluation, using a standardized protocol, of randomly selected out-patients was made. Joint hypermobility was measured by two scales in wide clinical use (Beighton and Contompasis), skin hyperextensibility was assessed on the dorsum of the hand, and skin thickness and light transmissibility was measured at the same site with a modified Harpenden caliper. The setting was an out-patient medical genetics clinic at an urban teaching hospital in Baltimore, Maryland, USA. The subjects comprised 27 children and 48 adults who met strict diagnostic criteria for the Marfan syndrome. In patients less than 18 yr old, 70% had experienced at least one locomotor syndrome, and 40% had had multiple symptoms, of which arthralgia, myalgia and ligamentous injury were the most frequent. Symptoms were absent in children younger than 5 yr. Thereafter, the number of symptoms increased with age. Considerable joint hyperextensibility (> 3/9 of Beighton's criteria) was present in 85%. While one-third had received orthopaedic attention, there had been little if any rheumatological input. In adult patients, locomotor symptoms had occurred in 96%, with 88% having experienced more than one complaint. Spinal pain, arthralgia, ligament injury and fracture were the most common. Most (81%) of the adults had some (> 1/9), and 56% had considerable (> 2/9) evidence of joint hypermobility. Only 20% had received specialist attention for their locomotor symptoms. Skin changes are documented in the Marfan syndrome for the first time in this study.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunohistochemical localization of fibrillin in human ocular tissues. Relevance to the Marfan syndrome

OBJECTIVE

To better understand the ocular manifestations of the Marfan syndrome, we investigated the distribution of fibrillin in normal human ocular tissues. Fibrillin, a microfibrillar glycoprotein component of the extracellular matrix, has been found to be the defective gene product in the Marfan syndrome.

METHODS

Frozen sections from seven pairs of normal eyes were stained with mouse anti-human fibrillin antibodies using the avidin-biotin immunoperoxidase technique.

RESULTS

In the anterior segment, the following exhibited positive staining for fibrillin: the lens capsule and zonules; connective tissues of the iris, ciliary body, ciliary processes, and conjunctiva; and the basement membrane regions of the corneal epithelium and endothelium of Schlemm's canal. Posteriorly, fibrillin localized to the lamina cribrosa, sclera, choroid, and Bruch's membrane.

CONCLUSIONS

Fibrillin is widely distributed in ocular connective tissues. The implications of defects in these tissues and the resultant ocular abnormalities in the Marfan syndrome such as ectopia lentis and glaucoma are discussed.

Composite graft repair of Marfan aneurysm of the ascending aorta: results in 150 patients

One hundred fifty consecutive Marfan patients undergoing composite graft repair of an ascending aorta aneurysm are reported. Twenty-six of the 150 patients had a preoperative dissection of the ascending aorta. There were no early deaths among 138 patients undergoing elective composite graft repair. There was one early death among 12 patients undergoing urgent operation; this patient arrived at the hospital with a rupturing aneurysm. Twenty-four of the 150 patients had mitral procedures; there were no early deaths in this group. There have been 14 late deaths among the 149 hospital survivors (9%). Actuarial survival of 150 patients at 1, 5, 10, and 14 years was 93%, 92%, 81%, and 73% respectively. Risk factors for early or late death were identified by multivariate analysis and only New York Heart Association class (III or IV) and male gender emerged as significant independent predictors of mortality. Late complications directly related to the composite graft have been gratifyingly low; only 2 patients had coronary dehiscence and 3 had thromboembolic events. Endocarditis emerged as an important late complication in 8 patients (5%). Two patients were successfully treated with antibiotics, 3 died before widespread availability of cryopreserved homografts, and 3 patients treated with antibiotics and homograft root replacement have had no evidence of recurrent infection. Seven patients with dissection in this series had aortic diameters of 6.5 cm or less. This experience supports the concept that composite graft repair in Marfan patients is mandated when the aneurysm reaches 5.5 to 6 cm, even in the asymptomatic patient.(ABSTRACT TRUNCATED AT 250 WORDS)

A molecular approach to the stratification of cardiovascular risk in families with Marfan's syndrome

BACKGROUND

The fibrillin gene encodes a protein in the extracellular matrix, and this protein is widely distributed in elastic tissues. The fibrillin gene is the site of mutations causing Marfan's syndrome. This disorder shows a high degree of clinical variability both between and within families. Each family appears to have a unique mutation in the fibrillin gene, which precludes the routine use of mutation screening for presymptomatic diagnosis of the disorder. The goal of this study was to develop a widely applicable method of molecular diagnosis.

METHODS

We used three newly characterized intragenic sites of normal DNA repeat-sequence variation (i.e., polymorphisms) as markers to follow the inheritance pattern of specific copies (alleles) of the fibrillin gene in multiple kindreds with various clinical features of Marfan's syndrome.

RESULTS

The polymorphic markers allowed identification of the particular copy of the fibrillin gene that cosegregated with Marfan's syndrome in 13 of the 14 families tested. In 11 families a definite presymptomatic diagnosis of Marfan's syndrome could be made in family members who had only equivocal manifestations of the disorder. In two other families, some family members demonstrated either classic Marfan's syndrome or a milder but closely related phenotype. The copy of the fibrillin gene that cosegregated with classic Marfan's syndrome was not inherited by family members with the latter, atypical, form of the disease. These milder phenotypes, previously diagnosed as Marfan's syndrome, were not associated with aortic involvement.

CONCLUSIONS

These results document the usefulness of novel polymorphic DNA repeat sequences in the presymptomatic diagnosis of Marfan's syndrome. Our findings also demonstrate that the various clinical phenotypes seen in selected families may be due not to single fibrillin mutations, but rather to different genetic alterations. These findings underscore the need for a modification of the current diagnostic criteria for Marfan's syndrome in order to achieve accurate risk assessment.