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.

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.

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 skipping of constitutive exons in vivo induced by nonsense mutations.

Nonsense mutations create a premature signal for the termination of translation of messenger RNA. Such mutations have been observed to cause a severe reduction in the amount of mutant allele transcript or to generate a peptide truncated at the carboxyl end. Analysis of fibrillin transcript from a patient with Marfan syndrome revealed the skipping of a constitutive exon containing a nonsense mutation. Similar results were observed for two nonsense mutations in the gene encoding ornithine delta-aminotransferase from patients with gyrate atrophy. All genomic DNA sequences flanking these exons that are known to influence RNA splicing were unaltered, which suggests that nonsense mutations can alter splice site selection in vivo.

Arterial tortuosity syndrome: clinical and molecular findings in 12 newly identified families.

Arterial tortuosity syndrome (ATS) is a rare autosomal recessive connective tissue disease, characterized by widespread arterial involvement with elongation, tortuosity, and aneurysms of the large and middle-sized arteries. Recently, SLC2A10 mutations were identified in this condition. This gene encodes the glucose transporter GLUT10 and was previously suggested as a candidate gene for diabetes mellitus type 2. A total of 12 newly identified ATS families with 16 affected individuals were clinically and molecularly characterized. In addition, extensive cardiovascular imaging and glucose tolerance tests were performed in both patients and heterozygous carriers. All 16 patients harbor biallelic SLC2A10 mutations of which nine are novel (six missense, three truncating mutations, including a large deletion). Haplotype analysis suggests founder effects for all five recurrent mutations. Remarkably, patients were significantly older than those previously reported in the literature (P=0.04). Only one affected relative died, most likely of an unrelated cause. Although the natural history of ATS in this series was less severe than previously reported, it does indicate a risk for ischemic events. Two patients initially presented with stroke, respectively at age 8 months and 23 years. Tortuosity of the aorta or large arteries was invariably present. Two adult probands (aged 23 and 35 years) had aortic root dilation, seven patients had localized arterial stenoses, and five had long stenotic stretches of the aorta. Heterozygous carriers did not show any vascular anomalies. Glucose metabolism was normal in six patients and eight heterozygous individuals of five families. As such, overt diabetes is not related to SLC2A10 mutations associated with ATS.

Attitudes antecedent to transition to self-management of a chronic genetic disorder.

Marfan syndrome (MFS) is the exemplar of chronic genetic disorders that require multiorgan system management by health care providers (HCPs) and lifelong self-management by affected individuals. This article describes the ways to facilitate transition to self-management (TSM) by the adolescent with MFS. This thematic content analysis uses data collected for a larger grounded theory investigation of TSM of a chronic genetic disorder in adolescents and focuses on the system issues related to transition. A total sample of 107 included three groups of participants: parents (n = 39), adolescents (n = 37, ages 14-21 years) and young adults (n = 16, ages 22-34 years) with MFS, and HCPs (n = 15), including physicians, genetic counselors, and nurses. Data were derived from 180 transcripts of audiotaped interviews and a sociodemographic survey. Frames of mind that are antecedent to transition were belief in the diagnosis, wanting to understand and appreciate the cause and effect of MFS, and willing to share responsibility in problem solving. These frames of mind occurred primarily within the context of the family relationship. Parents taught children self-surveillance as 'listening to one's body'. The parent's fears and need to stay involved in the child's health care slowed the child's independent work on self-management responsibilities. A systematic, institutionalized transition program for adolescents might involve parents and the child soon after diagnosis and incrementally build acknowledgment, understanding, and rapport.

Marfan syndrome: defective synthesis, secretion, and extracellular matrix formation of fibrillin by cultured dermal fibroblasts.

We studied the synthesis, secretion, and aggregation into the extracellular matrix of fibrillin by dermal fibroblasts from 26 probands with the Marfan syndrome. Cells from seven probands synthesized approximately half the normal amount of fibrillin when compared with intrafamilial or unrelated controls. Cells from an additional seven probands synthesized a normal amount of fibrillin but secreted the protein less efficiently than control cells. Cells from a further eight probands synthesized and secreted normal amounts of fibrillin but the protein was poorly incorporated into extracellular matrix. Cells from the remaining four probands were indistinguishable from control cells in their synthesis and processing of fibrillin. Cells from 18 family members of 10 of the probands were also studied. Cells from affected individuals in the same family had the same biochemical defect and those from unaffected family members were indistinguishable from controls. These results indicate that mutations in the gene that encodes fibrillin are responsible for the Marfan syndrome in the majority of individuals (confirming recent immunohistochemical and genetic linkage studies) and that a variety of mutations can produce the phenotype associated with the syndrome.

Marfan phenotype variability in a family segregating a missense mutation in the epidermal growth factor-like motif of the fibrillin gene.

To examine the associations among fibrillin gene mutations, protein function, and Marfan syndrome phenotype, we screened for alterations in the fibrillin coding sequence in patients with a range of manifestations and clinical severity. A cysteine to serine substitution at codon 1409 (C1409S) was identified in an epidermal growth factor (EGF)-like motif from one fibrillin allele which segregates with the disease phenotype through three generations of a family affected with the Marfan syndrome. This alteration was not observed in 60 probands from other families or in 88 unrelated normal individuals. The altered cysteine is completely conserved in all EGF-like motifs identified in fibrillin, and in all proteins that contain this motif. These observations strongly indicate that C1409S is the disease-producing mutation in this family. The phenotype of individuals carrying C1409S varied widely with respect to onset of disease, organ-system involvement, and clinical severity; certain affected adults were unaware of their status before being diagnosed through this investigation. We conclude that fibrillin gene defects cause familial Marfan syndrome, that mutations in the EGF-like motif of the fibrillin gene are not uniformly associated with severe disease, and that fibrillin genotype is not the sole determinant of Marfan phenotype.

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.

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.

Genetics and congenital heart disease: perspectives and prospects.

Elucidating the role of genes in the ontogenesis of the cardiovascular system is a task that involves many fields of inquiry. Recent dramatic advances in the molecular biology of transcription and its variations and the prospects for sequencing the entire human genome must not induce complacency; the major task of determining how a one-dimensional code specifies a three-dimensional structure demands an understanding of biologic systems considerably beyond the current level. The study of pathologic cardiovascular ontogeny is equally in need of new insight and fresh approaches. Although all clinicians might agree that genes are important contributors to both the etiology and the pathogenesis of congenital heart defects, with the exception of a few Mendelian conditions, this knowledge cannot be put to practice beyond crude statements of empirically determined probabilities. In this review, we selectively examine studies that are addressing what we perceive as provocative issues and suggest some areas, such as chaos theory, in which new ideas might be found.

Familial aortic dissecting aneurysm.

A family is described in which nine members over two generations had an aortic dissecting aneurysm or aortic or arterial dilation at a young age. The family has been followed up since 1977 after the death of a second teenager from a kindred of 11. None of the patients had the Marfan syndrome or a history of systemic hypertension. Three members died of ruptured aortic dissecting aneurysm and acute hemopericardium at 14, 18 and 24 years of age, respectively; a fourth member died suddenly at age 48 years, a few years after aortic repair for aneurysmal dilation. One member underwent surgical repair of an ascending aortic dissecting aneurysm at age 18 years and is still alive. Four members are currently under close medical observation for aortic or arterial dilation. Histologic examination of the aortic wall at autopsy or surgery in three patients revealed a loss of elastic fibers, deposition of mucopolysaccharide-like material in the media and cystic medial changes. Types I and III collagen from cultured fibroblasts appeared normal on gel electrophoresis. Results of indirect immunofluorescent studies of the elastin-associated microfibrillar fiber array in skin and fibroblast culture from multiple family members were also normal. This dramatic familial cluster of aortic dissecting aneurysm and aortic or arterial dilation suggests a genetically determined disease of autosomal dominant inheritance although the basic defect remains unknown.

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.

Respiratory complications of mucopolysaccharide storage disorders.

Twenty-one patients with the diagnosis of mucopolysaccharidosis or mucolipidosis and a history of respiratory complaints or thorough respiratory evaluation were studied retrospectively. Anatomic factors affecting respiratory status included: (i) upper airway narrowing by hypertrophied tongue, tonsils, adenoids, and mucous membranes; (ii) lower airway narrowing by glycosaminoglycan deposition within the tracheobronchial mucosa; (iii) decreased thoracic dimensions due to scoliosis and thoracic hyperkyphosis; and (iv) decreased abdominal dimensions due to lumbar hyperlordosis, gibbus formation and hepatosplenomegaly. Cardiac and neurologic involvement, while present, did not play primary roles in the development of respiratory disease. The functional consequences of these findings included increased risk of developing: (i) respiratory tract infections; (ii) airway compromise during or after anesthesia or sedation; (iii) dyspnea on exertion; (iv) obstructive lung disease; (v) obstructive sleep apnea; and (vi) cor pulmonale. A management approach is presented which can reduce the morbidity and mortality experienced by these patients.

Maternal and fetal complications of pregnancy in the Marfan syndrome.

The medical literature reports 32 women affected by the Marfan syndrome who had at least one pregnancy; 16 died of and four survived acute aortic dissection. Most of the women who suffered an aortic complication in association with pregnancy had pre-existing aortic regurgitation, aortic root dilatation or other severe cardiovascular problem. Because women with the Marfan syndrome usually desire children, our clinic records were reviewed and patients were contacted to determine a more representative estimate of maternal risks. The pregnancy histories of women with the Marfan syndrome were compared with those of spouses of men with the Marfan syndrome and those of mothers of a sporadic (new mutation) child with the Marfan syndrome. One of 26 women with the Marfan syndrome died shortly after pregnancy of endocarditis; she was the only woman to have a severe, pre-existing cardiovascular condition. The prevalences of milder pregnancy-associated cardiovascular and general complications did not differ among the study groups. The rate of early spontaneous abortion was higher in women with the Marfan syndrome than in either control group. These results suggest the risk of maternal death is low in women with the Marfan syndrome who have minimal cardiovascular disease. Women with the Marfan syndrome should be counseled regarding pregnancy risks only after review of their cardiovascular status, including an echocardiographically determined aortic root diameter.

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.

Ehlers-Danlos syndrome with abnormal collagen fibrils, sinus of Valsalva aneurysms, myocardial infarction, panacinar emphysema and cerebral heterotopias.

A 30 year old woman with marked joint hypermobility had severe, progressive lung disease, seizures, aneurysms of the sinuses of Valsalva and myocardial infarction documented during life. She died of intractable ventricular fibrillation, and postmortem examination showed myocardial injury in the distribution of the left coronary artery but no occlusive coronary artery disease. Severe panacinar emphysema was found in the lungs. Cerebral heterotopias with peculiar vascularization were present and were a likely cause of the seizure disorder. Electron microscopy showed dermal collagen fibrils to be heterogeneous in size, reduced in number, and irregular and frayed in appearance. This patient had a form of the Ehlers-Danlos syndrome, different from the 10 distinct variants described thus far, associated with lethal internal manifestations.

Diagnosis and management of infantile marfan syndrome.

Marfan syndrome is infrequently diagnosed early in infancy. The experience of the authors with 22 severely affected infants diagnosed as having Marfan syndrome in the first 3 months of life is described and the literature on 32 additional infants with Marfan syndrome is reviewed. It was found that serious cardiac pathology (82% of the patients described in the article, 94% of those described in the literature) may be present at birth, and that congenital contractures (64% of our cases, 47% of literature cases) are often an associated finding. Other useful clinical findings included arachnodactyly, dolichocephaly, a characteristic facies, a high-arched palate, micrognathia, hyperextensible joints, pes planus, anterior chest deformity, iridodenesis, megalocornea, and dislocated lenses. Echocardiography was useful as a noninvasive method for defining the extent of cardiovascular involvement and following its course. Characteristic cardiac findings in early life included mitral valve prolapse, valvular regurgitation, and aortic root dilation. Cardiac function ranged from normal to poor, with a tendency to worsen. Of the 22 cases 3 infants died during the first year of life. Morbidity and mortality may be high when Marfan syndrome is diagnosed during infancy, and prompt recognition of this phenotype can facilitate management and counseling. Most such severe cases appear to be due to a sporadic mutation in a single germ cell of one parent. Many familial cases may have milder manifestations, be more difficult to detect during infancy, and have a better prognosis.

The Marfan syndrome in early childhood: analysis of 15 patients diagnosed at less than 4 years of age.

The clinical, cardiac and echocardiographic features were reviewed of 15 consecutive infants and children with the Marfan syndrome who presented at less than 4 years of age. The 10 females and 5 males were diagnosed at a mean age of 18 months (range 2 days to 3.5 years); 13 were followed up for a mean of 45 months (range 8 to 109 months) and 2 were lost to follow-up. On first evaluation, 5 patients had mitral regurgitation (MR) and none had aortic regurgitation (AR). Echocardiography showed aortic root dilatation in 9 and mitral valve prolapse (MVP) in 9; only 2 patients had a normal echocardiogram. At follow-up examination, all patients had aortic root dilatation; the rate of increase in aortic root diameter was generally greater than predicted on the basis of body surface area. One patient had AR at age 10 years. All 13 patients had MVP; 9 had progressive mitral valve dysfunction and 4 had mitral valve replacement. One patient died immediately postoperatively. Thus, aortic root dilatation is usually present in early childhood and serves as an objective indicator of the Marfan syndrome. MVP is common and MR, which may require valve replacement, is the leading cause of cardiovascular morbidity in childhood. Echocardiography is useful in the diagnosis and routine management of infants and children in whom the Marfan syndrome is suspected.