Dorothy Halliday

Effect of Mutation Type and Location on Clinical Outcome in 1,013 Probands with Marfan Syndrome or Related Phenotypes and FBN1 Mutations: An International Study

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

Clinical and Molecular Study of 320 Children With Marfan Syndrome and Related Type I Fibrillinopathies in a Series of 1009 Probands With Pathogenic FBN1 Mutations

From a large series of 1009 probands with pathogenic FBN1 mutations, data for 320 patients <18 years of age at the last follow-up evaluation were analyzed (32%). At the time of diagnosis, the median age was 6.5 years. At the last examination, the population was classified as follows: neonatal Marfan syndrome, 14%; severe Marfan syndrome, 19%; classic Marfan syndrome, 32%; probable Marfan syndrome, 35%. Seventy-one percent had ascending aortic dilation, 55% ectopia lentis, and 28% major skeletal system involvement. Even when aortic complications existed in childhood, the rates of aortic surgery and aortic dissection remained low (5% and 1%, respectively). Some diagnostic features (major skeletal system involvement, striae, dural ectasia, and family history) were more frequent in the 10- to <18-year age group, whereas others (ascending aortic dilation and mitral abnormalities) were more frequent in the population with neonatal Marfan syndrome. Only 56% of children could be classified as having Marfan syndrome, according to international criteria, at their last follow-up evaluation when the presence of a FBN1 mutation was not considered as a major feature, with increasing frequency in the older age groups. Eighty-five percent of child probands fulfilled international criteria after molecular studies, which indicates that the discovery of a FBN1 mutation can be a valuable diagnostic aid in uncertain cases. The distributions of mutation types and locations in this pediatric series revealed large proportions of probands carrying mutations located in exons 24 to 32 (33%) and in-frame mutations (75%). Apart from lethal neonatal Marfan syndrome, we confirm that the majority of clinical manifestations of Marfan syndrome increase with age, which emphasizes the poor applicability of the international criteria to this diagnosis in childhood and the need for follow-up monitoring in cases of clinical suspicion of Marfan syndrome.

Cardiovascular manifestations in men and women carrying a FBN1 mutation

AIMS In patients with Marfan syndrome and other type-1 fibrillinopathies, genetic testing is becoming more easily available, leading to the identification of mutations early in the course of the disease. This study evaluates the cardiovascular (CV) risk associated with the discovery of a fibrillin-1 (FBN1) mutation. METHODS AND RESULTS A total of 1,013 probands with pathogenic FBN1 mutations were included, among whom 965 patients [median age: 22 years (11-34), male gender 53%] had data suitable for analysis. The percentage of patients with an ascending aortic (AA) dilatation increased steadily with increasing age and reached 96% (95% CI: 94-97%) by 60 years. The presence of aortic events (dissection or prophylactic surgery) was rare before 20 years and then increased progressively, reaching 74% (95% CI: 67-81%) by 60 years. Compared with women, men were at higher risk for AA dilatation [≤ 30 years: 57% (95% CI: 52-63) vs. 50% (95% CI: 45-55), P = 0.0076] and aortic events [≤ 30 years: 21% (95% CI: 17-26) vs. 11% (95% CI: 8-16), P < 0.0001; adjusted HR: 1.4 (1.1-1.8), P = 0.005]. The prevalence of mitral valve (MV) prolapse [≤ 60 years: 77% (95% CI: 72-82)] and MV regurgitation [≤ 60 years: 61% (95% CI: 53-69)] also increased steadily with age, but surgery limited to the MV remained rare [≤ 60 years: 13% (95% CI: 8-21)]. No difference between genders was observed (for all P> 0.20). From 1985 to 2005 the prevalence of AA dilatation remained stable (P for trend = 0.88), whereas the percentage of patients with AA dissection significantly decreased (P for trend = 0.01). CONCLUSION The CV risk remains important in patients with an FBN1 gene mutation and is present throughout life, justifying regular aortic monitoring. Aortic dilatation or dissection should always trigger suspicion of a genetic background leading to thorough examination for extra-aortic features and comprehensive pedigree investigation.

Contribution of molecular analyses in diagnosing Marfan syndrome and type I fibrillinopathies: an international study of 1009 probands

Background: The diagnosis of Marfan syndrome (MFS) is usually initially based on clinical criteria according to the number of major and minor systems affected following international nosology. The number of FBN1 mutation carriers, at risk of aortic complications who would not be properly diagnosed based only on clinical grounds, is of growing importance owing to the increased availability of molecular screening. The aim of the study was to identify patients who should be considered for FBN1 mutation screening. Methods: Our international series included 1009 probands with a known FBN1 mutation. Patients were classified as either fulfilling or not fulfilling “clinical” criteria. In patients with unfulfilled “clinical” criteria, we evaluated the percentage of additional patients who became positive for international criteria when the FBN1 mutation was considered. The aortic risk was evaluated and compared in patients fulfilling or not fulfilling the “clinical” international criteria. Results: Diagnosis of MFS was possible on clinical grounds in 79% of the adults, whereas 90% fulfilled the international criteria when including the FBN1 mutation. Corresponding figures for children were 56% and 85%, respectively. Aortic dilatation occurred later in adults with unfulfilled “clinical criteria” when compared to the Marfan syndrome group (44% vs 73% at 40 years, p<0.001), but the lifelong risk for ascending aortic dissection or surgery was not significantly different in both groups. Conclusions: Because of its implications for aortic follow-up, FBN1 molecular analysis is recommended in newly suspected MFS when two systems are involved with at least one major system affected. This is of utmost importance in patients without aortic dilatation and in children.

Cranial meningiomas in 411 neurofibromatosis type 2 (NF2) patients with proven gene mutations: clear positional effect of mutations, but absence of female severity effect on age at onset

Background Meningiomas have been reported to occur in approximately 50% of neurofibromatosis type 2 (NF2) patients. The NF2 gene is commonly biallelically inactivated in both schwannomas and meningiomas. The spectrum of NF2 mutations consists mainly of truncating (nonsense and frameshift) mutations. A smaller number of patients have missense mutations, which are associated with a milder disease phenotype. Methods This study analysed the cumulative incidence and gender effects as well as the genotype–phenotype correlation between the position of the NF2 mutation and the occurrence of cranial meningiomas in a cohort of 411 NF2 patients with proven NF2 mutations. Results and conclusion Patients with mutations in exon 14 or 15 were least likely to develop meningiomas. Cumulative risk of cranial meningioma to age 50 years was 70% for exons 1–3, 81% for exons 4–6, 49% for exons 7–9, 56% for exons 10–13, and 28% for exons 14–15. In the cohort of 411 patients, no overall gender bias was found for occurrence of meningioma in NF2 disease. Cumulative incidence of meningioma was close to 80% by 70 years of age for both males and females, but incidence by age 20 years was slightly increased in males (male 25%, female 18%; p=0.023). Conversely, an increased risk of meningiomas in women with mosaic NF2 disease was also found.

Twelve novel FBN1 mutations in Marfan syndrome and Marfan related phenotypes test the feasibility of FBN1 mutation testing in clinical practice

Marfan syndrome (MFS) is one of the major heritable disorders of connective tissue with a prevalence of between 1 in 5-10 000.1,2 It is characterised by features in the cardiovascular, ocular, and musculoskeletal systems and the Ghent criteria form a useful framework for its diagnosis.3 Mutations in FBN1 encoding the extracellular matrix protein fibrillin-1 classically cause MFS.4 Fibrillin-1, comprising multiple repeating subunits, of which the most common is the calcium binding epidermal growth factor (cbEGF) domain, is a key component of 10-12 nm microfibrils.5 Mutation detection has not been performed routinely in MFS because of the size and complexity of FBN1, which contains 65 exons extending over 200 kb of genomic DNA.5,6 Mutations are nearly always specific to each family and to date ∼300 mutations have been reported.7–10 FBN1 mutations have been found in 20-80% of patients with MFS depending upon the clinical selection of patients and the mutation detection method used.11–17 FBN1 mutations have been reported in a wide range of phenotypes in the Marfan spectrum1; neonatal MFS is associated with some FBN1 mutations in exons 24-3218; mutations of various types throughout FBN1 have been associated with classical MFS8; and FBN1 mutations have also been reported in many of the non-classical Marfan related phenotypes.1 The Ghent criteria propose that an FBN1 mutation is only of help diagnostically if it has been previously found in a person who independently meets the criteria for diagnosis of MFS.3 Other than mutations causing neonatal MFS, which occur in exons 24-32, correlation between genotype and phenotype is poor. The majority of patients with cysteine substitutions have classical MFS, and cysteine substitutions in exons 26-32 appear to be associated with classical disease manifesting early in life. …

Mutations in LZTR1 add to the complex heterogeneity of schwannomatosis

Objectives: We aimed to determine the proportion of individuals in our schwannomatosis cohort whose disease is associated with an LZTR1 mutation. Methods: We used exome sequencing, Sanger sequencing, and copy number analysis to screen 65 unrelated individuals with schwannomatosis who were negative for a germline NF2 or SMARCB1 mutation. We also screened samples from 39 patients with a unilateral vestibular schwannoma (UVS), plus at least one other schwannoma, but who did not have an identifiable germline or mosaic NF2 mutation. Results: We identified germline LZTR1 mutations in 6 of 16 patients (37.5%) with schwannomatosis who had at least one affected relative, 11 of 49 (22%) sporadic patients, and 2 of 39 patients with UVS in our cohort. Three germline mutation–positive patients in total had developed a UVS. Mosaicism was excluded in 3 patients without germline mutation in NF2, SMARCB1, or LZTR1 by mutation screening in 2 tumors from each. Conclusions: Our data confirm the relationship between mutations in LZTR1 and schwannomatosis. They indicate that germline mutations in LZTR1 confer an increased risk of vestibular schwannoma, providing further overlap with NF2, and that further causative genes for schwannomatosis remain to be identified.

Clinical and molecular predictors of mortality in neurofibromatosis 2: a UK national analysis of 1192 patients

Background Neurofibromatosis 2 (NF2) is an autosomal-dominant tumour predisposition syndrome characterised by bilateral vestibular schwannomas, considerable morbidity and reduced life expectancy. Although genotype–phenotype correlations are well established in NF2, little is known about effects of mutation type or location within the gene on mortality. Improvements in NF2 diagnosis and management have occurred, but their effect on patient survival is unknown. Methods We evaluated clinical and molecular predictors of mortality in 1192 patients (771 with known causal mutations) identified through the UK National NF2 Registry. Kaplan–Meier survival and Cox regression analyses were used to evaluate predictors of mortality, with jackknife adjustment of parameter SEs to account for the strong intrafamilial phenotypic correlations that occur in NF2. Results The study included 241 deaths during 10 995 patient-years of follow-up since diagnosis. Early age at diagnosis and the presence of intracranial meningiomas were associated with increased mortality, and having a mosaic, rather than non-mosaic, NF2 mutation was associated with reduced mortality. Patients with splice-site or missense mutations had lower mortality than patients with truncating mutations (OR 0.459, 95% CI 0.213 to 0.990, and OR 0.196, 95% CI 0.213 to 0.990, respectively). Patients with splice-site mutations in exons 6–15 had lower mortality than patients with splice-site mutations in exons 1–5 (OR 0.333, 95% CI 0.129 to 0.858). The mortality of patients with NF2 diagnosed in more recent decades was lower than that of patients diagnosed earlier. Conclusions Continuing advances in molecular diagnosis, imaging and treatment of NF2-associated tumours offer hope for even better survival in the future.

English consensus protocol evaluating candidacy for auditory brainstem and cochlear implantation in neurofibromatosis type 2

Objective Hearing loss resulting from bilateral vestibular schwannomas (VSs) has a significant effect on the quality of life of patients with neurofibromatosis Type 2 (NF2). A national consensus protocol was produced in England as a guide for cochlear implantation (CI) and auditory brainstem implantation (ABI) in these patients. Study Design Consensus statement. Setting English NF2 Service. Participants Clinicians from all 4 lead NF2 units in England. Main Outcome Measures A protocol for the assessment, insertion and rehabilitation of CI and ABI in NF2 patients. Results Patients should undergo more detailed hearing assessment once their maximum aided speech discrimination score falls below 50% in the better hearing ear. Bamford-Kowal-Bench sentence testing scores below 50% should trigger assessment for auditory implantation, as recommended by the National Institute for Clinical Excellence guidelines on CI. Where this occurs in patients with bilateral stable VS or a unilateral stable VS where the contralateral cochlear nerve was lost at previous surgery, CI should be considered. Where VS surgery is planned, CI should be considered where cochlear nerve preservation is thought possible, otherwise an ABI should be considered. Intraoperative testing using electrically evoked auditory brainstem responses or cochlear nerve action potentials may be used to determine whether a CI or ABI is inserted. Conclusion The NF2 centers in England agreed on this protocol. Multisite, prospective assessments of standardized protocols for auditory implantation in NF2 provide an essential model for evaluating candidacy and outcomes in this challenging patient population.

The response of spinal cord ependymomas to bevacizumab in patients with neurofibromatosis Type 2

OBJECTIVE People with neurofibromatosis Type 2 (NF2) have a genetic predisposition to nervous system tumors. NF2-associated schwannomas stabilize or decrease in size in over half of the patients while they are receiving bevacizumab. NF2 patients treated with bevacizumab for rapidly growing schwannoma were retrospectively reviewed with regard to ependymoma prevalence and response to treatment. METHODS The records of 95 NF2 patients receiving bevacizumab were retrospectively reviewed with regard to spinal ependymoma prevalence and behavior. The maximum longitudinal extent (MLE) of the ependymoma and associated intratumoral or juxtatumoral cysts were measured on serial images. Neurological changes and patient function were reviewed and correlated with radiological changes. RESULTS Forty-one of 95 patients were found to have ependymomas (median age 26 years; range 11-53 years). Thirty-two patients with a total of 71 ependymomas had scans appropriate for serial assessment with a mean follow-up of 24 months (range 3-57 months). Ependymomas without cystic components showed minimal change in MLE. Twelve patients had ependymomas with cystic components or syringes. In these patients, reductions in MLE were observed, particularly due to decreases in the cystic components of the ependymoma. Clinical improvement was seen in 7 patients, who all had cystic ependymomas. CONCLUSIONS Bevacizumab treatment in NF2 patients with spinal cord ependymomas results in a decrease in the size of intratumoral and juxtatumoral cysts as well as adjacent-cord syringes and a decrease in cord edema. This may provide clinical benefit in some patients, although the changes do not meet the current criteria for radiological tumor response.