Clinical and genetic aspects of neurofibromatosis 1

Activated Ras as a Therapeutic Target: Constraints on Directly Targeting Ras Isoforms and Wild-Type versus Mutated Proteins

The ability to selectively and directly target activated Ras would provide immense utility for treatment of the numerous cancers that are driven by oncogenic Ras mutations. Patients with disorders driven by overactivated wild-type Ras proteins, such as type 1 neurofibromatosis, might also benefit from progress made in that context. Activated Ras is an extremely challenging direct drug target due to the inherent difficulties in disrupting the protein:protein interactions that underlie its activation and function. Major investments have been made to target Ras through indirect routes. Inhibition of farnesyl transferase to block Ras maturation has failed in large clinical trials. Likely reasons for this disappointing outcome include the significant and underappreciated differences in the isoforms of Ras. It is still plausible that inhibition of farnesyl transferase will prove effective for disease that is driven by activated H-Ras. The principal current focus of drugs entering clinic trial is inhibition of pathways downstream of activated Ras, for example, trametinib, a first-in-class MEK inhibitor. The complexity of signaling that is driven by activated Ras indicates that effective inhibition of oncogenic transduction through this approach will be difficult, with resistance being likely to emerge through switch to parallel pathways. Durable disease responses will probably require combinatorial block of several downstream targets.

Small G Proteins in the Cardiovascular System: Physiological and Pathological Aspects

Small G proteins exist in eukaryotes from yeast to human and constitute the Ras superfamily comprising more than 100 members. This superfamily is structurally classified into five families: the Ras, Rho, Rab, Arf, and Ran families that control a wide variety of cell and biological functions through highly coordinated regulation processes. Increasing evidence has accumulated to identify small G proteins and their regulators as key players of the cardiovascular physiology that control a large panel of cardiac (heart rhythm, contraction, hypertrophy) and vascular functions (angiogenesis, vascular permeability, vasoconstriction). Indeed, basal Ras protein activity is required for homeostatic functions in physiological conditions, but sustained overactivation of Ras proteins or spatiotemporal dysregulation of Ras signaling pathways has pathological consequences in the cardiovascular system. The primary object of this review is to provide a comprehensive overview of the current progress in our understanding of the role of small G proteins and their regulators in cardiovascular physiology and pathologies.

Schwannoma in neurofibromatosis type 1: a pitfall for detecting malignancy by metabolic imaging

Neurofibromatosis type 1 (NF1) is a neurocutaneous syndrome characterized by the development of multiple peripheral nerve sheath tumors, the majority of which are benign neurofibromas. However, malignant peripheral nerve sheath tumors (MPNSTs) occur with a 10 % lifetime risk in patients with NF1, often developing within a neurofibroma. When clinical suspicion for an MPNST arises, imaging with FDG PET and MRI is performed to characterize a peripheral tumor for potential malignancy. In this report, we describe a patient with NF-1 who had two peripheral tumors with similar features by PET, both suspicious for MPNST, but differing features by MRI, one of which was subsequently determined to be an MPNST and the second to be a schwannoma.

Neuropsychological profile in adults with neurofibromatosis type 1 compared to a control group

BACKGROUND

Neurofibromatosis type 1 (NF1) is a common inherited autosomal dominant condition, characterised by multiple café-au-lait macules, axillary and/or inguinal freckling, iris Lisch nodules and tumours of the nervous system such as neurofibromas and optic pathway gliomas. At the same time, NF1 is frequently associated with intellectual disabilities across several neuropsychological domains. Existing neuropsychological data in NF1 adults are limited and sometimes contradictory. Moreover, most studies use a non-IQ-controlled norm group for comparison. This study sought to investigate specific neuropsychological characteristics in intellectual abilities unrelated to the global intellectual capacity.

METHOD

Twenty NF1 adults and an IQ-, age- and gender-matched control group completed a comprehensive neuropsychological test battery composed of specific cognitive tests investigating visual-spatial abilities and memory, auditory memory, selective and sustained attention and executive functioning. A short version of the Wechsler Adult Intelligence Scale - III was also administered to both groups.

RESULTS

Norm comparison showed that both groups perform poorly on most neuropsychological functions, except for sustained attention. However, comparison with the IQ-matched control group showed significantly lower scores on visual-spatial abilities and memory, on auditory working memory and on tests for cognitive flexibility in NF1 adults. Nevertheless, as the significant difference in average estimated IQ score between the NF1 group and the selected control group almost reaches the 5% significance level, further analysis is needed to include IQ as a covariate. Eventually, problems in visual-spatial skills and auditory long-term memory seem to be specific NF1-related deficits, while problems in attention and executive functioning are particularly related to their general lowered intellectual abilities.

CONCLUSION

Taking into account that primary visual perception problems could be part of a more general central coherence deficit while interpreting auditory memory problems as possibly related to deficits in language use and comprehension, this idea also fits with the observation of several problems in social information processing and functioning of NF1 persons.

Genomic imbalance of HMMR/RHAMM regulates the sensitivity and response of malignant peripheral nerve sheath tumour cells to aurora kinase inhibition

Malignant peripheral nerve sheath tumours (MPNST) are rare, hereditary cancers associated with neurofibromatosis type I. MPNSTs lack effective treatment options as they often resist chemotherapies and have high rates of disease recurrence. Aurora kinase A (AURKA) is an emerging target in cancer and an aurora kinase inhibitor (AKI), termed MLN8237, shows promise against MPNST cell lines in vitro and in vivo. Here, we test MLN8237 against two primary human MPNST grown in vivo as xenotransplants and find that treatment results in tumour cells exiting the cell cycle and undergoing endoreduplication, which cumulates in stabilized disease. Targeted therapies can often fail in the clinic due to insufficient knowledge about factors that determine tumour susceptibilities, so we turned to three MPNST cell-lines to further study and modulate the cellular responses to AKI. We find that the sensitivity of cell-lines with amplification of AURKA depends upon the activity of the kinase, which correlates with the expression of the regulatory gene products TPX2 and HMMR/RHAMM. Silencing of HMMR/RHAMM, but not TPX2, augments AURKA activity and sensitizes MPNST cells to AKI. Furthermore, we find that AURKA activity is critical to the propagation and self-renewal of sphere-enriched MPNST cancer stem-like cells. AKI treatment significantly reduces the formation of spheroids, attenuates the self-renewal of spheroid forming cells, and promotes their differentiation. Moreover, silencing of HMMR/RHAMM is sufficient to endow MPNST cells with an ability to form and maintain sphere culture. Collectively, our data indicate that AURKA is a rationale therapeutic target for MPNST and tumour cell responses to AKI, which include differentiation, are modulated by the abundance of HMMR/RHAMM.

Neurofibromatosis type 1 with bladder involvement

Neurofibromatosis type 1 is an autosomal dominant transmitted disease with various clinical manifestations. The bladder is the most commonly affected organ in the genitourinary system. The malignant transformation of the disease is rare, and unlike malign tumors, the treatment option for benign disease is usually conservative. The size and localization of the mass determine the symptoms, most of which are usually not specific. In this paper, we aim to present a 15-year-old patient with neurofibromatosis type 1 with bladder involvement. The clinical presentation and treatment options of this disease are discussed in the light of the literature.

Neurofibromatosis type 1 and pregnancy complications: a population-based study

OBJECTIVE

The objective of the study was to determine whether vascular and other complications are more common in pregnant women with neurofibromatosis type 1 (NF1).

STUDY DESIGN

We performed a population-based retrospective cohort study using the US Nationwide Inpatient Sample, 1988-2009, defining a cohort of pregnancy-related hospitalizations with an associated diagnosis of NF1 and comparing it with the control group not associated with NF1. Multivariable logistic regression was used to adjust for suspected confounders.

RESULTS

Among 19 million pregnancy-related admissions between 1988 and 2009, we identified 1553 associated with NF1 (prevalence 0.008%). A diagnosis of NF1 in delivering mothers was associated with gestational hypertension (adjusted odds ratio [AOR], 1.6, 95% confidence interval [CI], 1.2-2.0), preeclampsia (AOR, 2.8, 95% CI, 2.3-3.4), intrauterine growth restriction (AOR, 4.6, 95% CI, 3.7-5.6), cerebrovascular disease (OR, 8.1, 95% CI, 2.6-25.4), preterm labor (AOR, 1.6, 95% CI, 1.4-1.9), and cesarean delivery (AOR, 2.0, 95% CI, 1.8-2.3). Women with NF1 were not significantly more likely to have deep venous thrombosis/pulmonary embolism, acute cardiac events, or stillbirth or to die during their hospitalizations compared with the general obstetric population.

CONCLUSION

NF1 was associated with increased maternal morbidity in pregnancy (including hypertensive and cerebrovascular complications) but not increased maternal mortality. Obstetricians should be aware of the potential for increased antenatal and peripartum complications among women with NF1.

Intracerebral schwannomas: a rare disease with varying natural history

Although intracerebral schwannomas are typically regarded as benign intracranial tumors, malignancy and recurrence have been reported among patients harboring such neoplasms. The available literature consists of case reports and small series that present variable characteristics distinguishing these unusual lesions. Little advancement has been made to further the understanding and management of these tumors. The authors present 3 cases from their institution that highlight the difference between typical benign intracerebral schwannomas and histopathological variants that may portend more aggressive behavior. Also provided is a review of the literature in the hope of gaining a better understanding of these rare tumors.

Mutation spectrum of NF1 and clinical characteristics in 78 Korean patients with neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is one of the most common autosomal dominant disorders in humans. NF1 is caused by mutations of the NF1 gene. Mutation detection is complex owing to the large size of the NF1 gene, the presence of pseudogenes, and the great variety of mutations. Also, few probable genotype-phenotype correlations have been found in NF1. In this study 78 Korean patients from 60 families were screened for NF1 mutations. Mutation analysis of the entire coding region and flanking splice sites was carried out and included the use of a combination of reverse transcription polymerase chain reaction, multiplex ligation probe amplification, or fluorescence in situ hybridization. Mutation spectrum and genotype-phenotype relationship were assessed. Fifty-two distinct NF1 mutations were identified in 60 families. The mutations included 30 single base substitutions (12 missense and 18 nonsense), 11 missplicing mutations, seven small insertion or deletions, and four gross deletions. Sixteen (30.8%) mutations were novel; c.1A>G, c.2033_2034insC, c.2540T>C, c.4537C>T, c.5546G>A, c.6792C>A, and c.6792C>G were recurrently identified. The mutations were evenly distributed across exon 1 through intron 47 of NF1, and no mutational hot spots were found. A genotype-phenotype analysis suggests that there is no clear relationship between specific mutations and clinical features. This analysis revealed a wide spectrum of NF1 mutations in Korean patients. As technologies advance in molecular genetics, the mutation detection rate will increase. Considering that 30.8% of detected mutations were novel, exhaustive mutation analysis of NF1 may be an important tool in early diagnosis and genetic counseling.

Diffuse ganglioneuromatosis and plexiform neurofibroma of the urinary bladder: an uncommon cause of severe urological disease in an infant

Neurofibromatosis of the urinary tract occurs infrequently: fewer than 70 cases with bladder involvement have been reported to date and of these, only 25 cases occurred in the pediatric population. We describe an unusual case of plexiform neurofibroma and diffuse ganglioneuromatosis of the bladder in a small infant, diagnosed with neurofibromatosis 1 (NF1) at 3 months of age. At the moment, there are no established criteria for the treatment of this rare lesion. Due to the high morbidity, although not very common, bladder involvement should be considered in infants with NF1.

Spectrum and prevalence of vasculopathy in pediatric neurofibromatosis type 1

To describe the spectrum and associated clinical features of peripheral and cerebral vasculopathy in pediatric patients with neurofibromatosis type 1, children seen at a single center from 2000 to 2010 with appropriate imaging studies were identified. Scans were assessed for vascular disease by 2 pediatric neuroradiologists. Of 181 children, 80 had pertinent imaging studies: 77 had brain imaging, 6 had peripheral imaging, and 3 had both. Vasculopathy was identified in 14/80 children (18%, minimum prevalence of 14/181; 8%). Of those with vascular abnormalities, 2/14 had peripheral vasculopathy (1% minimum prevalence) and 12/14 had cerebrovascular abnormalities (7% minimum prevalence). No associations were found between vasculopathy and common clinical features of neurofibromatosis type 1, including optic pathway glioma, plexiform neurofibroma, skeletal abnormalities, attention-deficit hyperactivity disorder (ADHD), or suspected learning disability. Both peripheral and cerebral vasculopathy are important complications of pediatric neurofibromatosis type 1 and should be considered in the management of this complex disease.

Neurofibromatosis: types 1 and 2

Neurofibromatosis types 1 and 2 are a group of neurocutaneous syndromes resulting from disorders in cell regulation. Despite sharing a common name, neurofibromatosis types 1 and 2 are quite distinct phakomatoses, both clinically and genetically.

Moyamoya syndrome associated with neurofibromatosis Type 1: perioperative and long-term outcome after surgical revascularization

OBJECT

Children with neurofibromatosis Type 1 (NF1) can present with progressive arteriopathy of the branches of the internal carotid artery consistent with moyamoya syndrome. Clinical symptoms, radiographic evidence of ischemia, and the potential for disease progression may necessitate surgical revascularization to minimize the risk of stroke and progressive neurological deficits. This study aims to evaluate the presentation and surgical outcomes of these patients by reviewing clinical, radiographic, and angiographic data.

METHODS

A retrospective review was conducted of clinical and radiographic records of all children with NF1 who were diagnosed with moyamoya syndrome and underwent surgical revascularization between January 1988 and April 2012 at Boston Children's Hospital.

RESULTS

During this period, 39 patients (27 female and 12 male, ages 0.2-19.3 years) had both NF1 and moyamoya syndrome, of whom 32 underwent surgical revascularization with pial synangiosis. Of the 32 patients treated by surgical revascularization, 21 (66%) manifested ischemic symptoms and 18 (56%) had radiographic evidence of prior stroke at the time of moyamoya diagnosis. In total, 25 of 32 patients developed neurological symptoms prior to surgical intervention. Only 1 patient presented with hemorrhage. The average age at first surgery was 8.1 years (range 0.5-15.6 years). Perioperative complications in the first 7 days included stroke (n = 2), transient ischemic attack (n = 1), and infection (n = 1). Twenty-two patients had more than 6 months of follow-up, with an average clinical and radiographic postoperative follow-up period of 80.2 months (range 9.4-257.1 months). Of those patients with long-term follow-up, 21 (95%) of 22 demonstrated stable or improved neurological status despite radiographic evidence of moyamoya progression in 48% of patients.

CONCLUSIONS

Children with NF1-associated moyamoya syndrome are often diagnosed prior to development of fixed neurological deficits as a consequence of imaging studies obtained for other manifestations of NF1. The clinical, radiographic, and angiographic features in this population are comparable to primary moyamoya disease, with the exception of patients treated with cranial irradiation, who may be at greater risk for both stroke as well as perioperative complications. Despite radiographic evidence of progressive stenosis in 48% of patients, nearly all demonstrated stable or improved neurological status after surgical revascularization. Surgical revascularization for children with NF1 appears safe and is protective against further ischemic and neurological damage, with a 27-fold reduction in stroke rate.

Development of the adult PedsQL™ neurofibromatosis type 1 module: initial feasibility, reliability and validity

BACKGROUND

Neurofibromatosis type 1 (NF1) is a common autosomal dominant genetic disorder with significant impact on health-related quality of life (HRQOL). Research in understanding the pathogenetic mechanisms of neurofibroma development has led to the use of new clinical trials for the treatment of NF1. One of the most important outcomes of a trial is improvement in quality of life, however, no condition specific HRQOL instrument for NF1 exists. The objective of this study was to develop an NF1 HRQOL instrument as a module of PedsQL™ and to test for its initial feasibility, internal consistency reliability and validity in adults with NF1.

METHODS

The NF1 specific HRQOL instrument was developed using a standard method of PedsQL™ module development - literature review, focus group/semi-structured interviews, cognitive interviews and experts' review of initial draft, pilot testing and field testing. Field testing involved 134 adults with NF1. Feasibility was measured by the percentage of missing responses, internal consistency reliability was measured with Cronbach's alpha and validity was measured by the known-groups method.

RESULTS

Feasibility, measured by the percentage of missing responses was 4.8% for all subscales on the adult version of the NF1-specific instrument. Internal consistency reliability for the Total Score (alpha =0.97) and subscale reliabilities ranging from 0.72 to 0.96 were acceptable for group comparisons. The PedsQL™ NF1 module distinguished between NF1 adults with excellent to very good, good, and fair to poor health status.

CONCLUSIONS

The results demonstrate the initial feasibility, reliability and validity of the PedsQL™ NF1 module in adult patients. The PedsQL™ NF1 Module can be used to understand the multidimensional nature of NF1 on the HRQOL patients with this disorder.

GABA deficit in the visual cortex of patients with neurofibromatosis type 1: genotype-phenotype correlations and functional impact

Alterations in the balance between excitatory and inhibitory neurotransmission have been implicated in several neurodevelopmental disorders. Neurofibromatosis type 1 is one of the most common monogenic disorders causing cognitive deficits for which studies on a mouse model (Nfl(+/-)) proposed increased γ-aminobutyric acid-mediated inhibitory neurotransmission as the neural mechanism underlying these deficits. To test whether a similar mechanism translates to the human disorder, we used magnetic resonance spectroscopy to measure γ-aminobutyric acid levels in the visual cortex of children and adolescents with neurofibromatosis type 1 (n = 20) and matched control subjects (n = 26). We found that patients with neurofibromatosis type 1 have significantly lower γ-aminobutyric acid levels than control subjects, and that neurofibromatosis type 1 mutation type significantly predicted cortical γ-aminobutyric acid. Moreover, functional imaging of the visual cortex indicated that blood oxygen level-dependent signal was correlated with γ-aminobutyric acid levels both in patients and control subjects. Our results provide in vivo evidence of γ-aminobutyric acidergic dysfunction in neurofibromatosis type 1 by showing a reduction in γ-aminobutyric acid levels in human patients. This finding is relevant to understand the physiological profile of the disorder and has implications for the identification of targets for therapeutic strategies.

Diffusion tensor imaging and fiber tractography in brain malformations

Diffusion tensor imaging (DTI) is an advanced MR technique that provides qualitative and quantitative information about the micro-architecture of white matter. DTI and its post-processing tool fiber tractography (FT) have been increasingly used in the last decade to investigate the microstructural neuroarchitecture of brain malformations. This article aims to review the use of DTI and FT in the evaluation of a variety of common, well-described brain malformations, in particular by pointing out the additional information that DTI and FT renders compared with conventional MR sequences. In addition, the relevant existing literature is summarized.

NF1 deficiency causes Bcl-xL upregulation in Schwann cells derived from neurofibromatosis type 1-associated malignant peripheral nerve sheath tumors

Since the bi-allelic inactivation of both neurofibromin 1 (NF1) gene alleles (NF1(-/-)) in Schwann cells (SCs) is common in both benign plexiform neurofibromas (PNs) and malignant peripheral nerve sheath tumors (MPNSTs) in patients with neurofibromatosis type 1 (NF1), other genetic alterations in SCs may be required for tumor progression of PNs to MPNSTs. We found that the anti-apoptotic Bcl-xL protein is upregulated in MPNST tissues compared to PN tissues from patients with NF1 by immunohistological staining. In addition, we investigated whether Bcl-xL is upregulated in SCs derived from MPNSTs and found a significantly higher Bcl-xL expression level in sNF96.2 MPNST-derived SCs compared to normal human SCs (HSCs). We also discovered that the increased Bcl-xL expression caused an increase in drug resistance to doxorubicin in MPNST-derived SCs. Manipulation of NF1 gene expression levels by treatment with small interfering RNA (siRNA) and overexpression of the neurofibromin GAP-related domain (NF1-GRD) demonstrated that upregulated Bcl-xL expression in MPNST-derived SCs was caused by NF1 deficiency. Treatment with the Erk1/2 inhibitor, PD98059, resulted in a slight increase in Bcl-xL levels in neurofibromin-depleted normal HSCs, indicating that Bcl-xL upregulation in MPNST-derived SCs is mediated by activated Erk1/2, which is a Ras downstream protein regulated by neurofibromin. As the reduction of Bcl-xL expression restored sensitivity to doxorubicin-induced apoptosis in sNF96.2 cells, we examined the effect of the small molecule Bcl-xL inhibitor ABT-737 on sNF96.2 cells. A very low dose of ABT-737 combined with doxorubicin synergistically enhanced sensitivity to doxorubicin-induced apoptosis in sNF96.2 cells, suggesting that ABT-737 and doxorubicin may be a good combination to effectively treat NF1-associated MPNSTs with minimal side-effects. Collectively, our results suggest that upregulation of Bcl-xL in MPNST-derived SCs may be caused by the NF1 deficiency-mediated elevation in Ras/MAPK signaling and may provide a new potential chemotherapeutic target in patients with NF1 and MPNSTs.

Marrow signal changes observed in follow-up whole-body MRI studies in children and young adults with neurofibromatosis type 1 treated with imatinib mesylate (Gleevec) for plexiform neurofibromas

BACKGROUND

We observed bone marrow signal changes (BMSC) in patients with plexiform neurofibromas after treatment with imatinib mesylate (Gleevec).

OBJECTIVE

To evaluate the pattern and natural history of BMSC.

MATERIALS AND METHODS

The data were obtained from a pilot study of imatinib mesylate in patients with plexiform neurofibromas. All patients underwent baseline and sequential whole-body STIR 1.5-T MRI after treatment. The bone marrow signal on MRI was evaluated for abnormalities, location and pattern, and any change on follow-up studies.

RESULTS

The study group included 16 patients (8 males) with a median age of 14 years (range 4 to 25 years). The mean whole-body MRI follow-up duration was 1.9 years. Of the 16 patients, 14 (88%) developed BMSC. The signal change was asymmetrical in 9 of the 14 patients (64%). The appendicular skeleton was involved in all 14 patients and the axial skeleton in 3 patients (21%). BMSC was followed in 13 patients and decreased signal was seen in 9 patients (69%) after a mean duration of 1.3 years of treatment (range 0.6 to 2.9 years); no complications were observed.

CONCLUSION

BMSC appeared in most patients with neurofibromatosis type 1 following treatment with imatinib mesylate. BMSC was unusually asymmetrical and involved the lower extremities. On follow-up, BMSC often showed a decrease without complications.

Molecular heterogeneity in malignant peripheral nerve sheath tumors associated with neurofibromatosis type 1

Neurofibromatosis type-1 (NF1), resulting from NF1 gene loss of function, is characterized by an increased risk of developing benign and malignant peripheral nerve sheath tumors (MPNSTs). Whereas the cellular heterogeneity of NF1-associated tumors has been well studied, the molecular heterogeneity of MPNSTs is still poorly understood. Mutational heterogeneity within these malignant tumors greatly complicates the study of the underlying mechanisms of tumorigenesis. We have explored this molecular heterogeneity by performing loss of heterozygosity (LOH) analysis of the NF1, TP53, RB1, PTEN, and CDKN2A genes on sections of 10 MPNSTs derived from 10 unrelated NF1 patients. LOH data for the TP53 gene was found to correlate with the results of p53 immunohistochemical analysis in the same tumor sections. Further, approximately 70% of MPNSTs were found to display intra-tumoral molecular heterogeneity as evidenced by differences in the level of LOH between different sections of the same tumor samples. This study constitutes the first systematic analysis of molecular heterogeneity within MPNSTs derived from NF1 patients. Appreciation of the existence of molecular heterogeneity in NF1-associated tumors is important not only for optimizing somatic mutation detection, but also for understanding the mechanisms of NF1 tumorigenesis, a prerequisite for the development of specifically targeted cancer therapeutics.

Genotype-phenotype associations in neurofibromatosis type 1 (NF1): an increased risk of tumor complications in patients with NF1 splice-site mutations?

Neurofibromatosis type 1 (NF1) is a complex neurocutaneous disorder with an increased susceptibility to develop both benign and malignant tumors but with a wide spectrum of inter and intrafamilial clinical variability. The establishment of genotype-phenotype associations in NF1 is potentially useful for targeted therapeutic intervention but has generally been unsuccessful, apart from small subsets of molecularly defined patients. The objective of this study was to evaluate the clinical phenotype associated with the specific types of NF1 mutation in a retrospectively recorded clinical dataset comprising 149 NF1 mutation-known individuals from unrelated families. Each patient was assessed for ten NF1-related clinical features, including the number of café-au-lait spots, cutaneous and subcutaneous neurofibromas and the presence/absence of intertriginous skin freckling, Lisch nodules, plexiform and spinal neurofibromas, optic gliomas, other neoplasms (in particular CNS gliomas, malignant peripheral nerve sheath tumors (MPNSTs), juvenile myelomonocytic leukemia, rhabdomyosarcoma, phaechromocytoma, gastrointestinal stromal tumors, juvenile xanthogranuloma, and lipoma) and evidence of learning difficulties. Gender and age at examination were also recorded. Patients were subcategorized according to their associated NF1 germ line mutations: frame shift deletions (52), splice-site mutations (23), nonsense mutations (36), missense mutations (32) and other types of mutation (6). A significant association was apparent between possession of a splice-site mutation and the presence of brain gliomas and MPNSTs (p = 0.006). If confirmed, these findings are likely to be clinically important since up to a third of NF1 patients harbor splice-site mutations. A significant influence of gender was also observed on the number of subcutaneous neurofibromas (females, p = 0.009) and preschool learning difficulties (females, p = 0.022).

Whole-body MRI in neurofibromatosis: incidental findings and prevalence of scoliosis

OBJECTIVE

To demonstrate incidental findings and scoliosis on whole-body MRI (WBMRI) in patients with neurofibromatosis type 1 and 2 (NF1 & NF2, respectively), and schwannomatosis.

MATERIALS AND METHODS

Institutional review board approval and written informed consent were obtained for this prospective HIPAA-compliant study. A total of 247 subjects (141 with NF1, 55 with NF2, 51 with schwannomatosis; 132 women (53.5%); mean age, 41 years, range, 18-97 years) underwent WBMRI using coronal STIR (TR/TE: 4190/111 ms, TI: 150 ms) and T1-weighted images (TR/TE: 454/10 ms), 10-mm slice thickness, imaging time ~40 min. Images were reviewed for the presence of incidental findings, outside of nerve sheath tumors. The presence of scoliosis was recorded and curve morphology was assessed and quantified.

RESULTS

Incidental findings other than scoliosis were recorded in 104/247 (42%) patients, most often affecting the musculoskeletal system (65/247 patients, 26%). We found 16/247 (6.5%) significant incidental findings likely to affect clinical management, including avascular necrosis of bone in eight patients (five with NF2), eight insufficiency fractures, and four non-neurogenic neoplasms (Hodgkin's lymphoma, liposarcoma, dermoid cyst, large uterine myoma requiring excision). Scoliosis was seen in 50/247 patients (20%), including 8/55 with NF2 (15%) and 11/51 with schwannomatosis (22%).

CONCLUSIONS

Incidental findings in the neurofibromatoses frequently involve the skeleton. Given the relatively high incidence of unsuspected osteonecrosis and stress fractures, close attention to the skeleton on WBMRI is advised. In addition, knowledge of common incidental findings can help clinicians prepare patients who undergo WBMRI for potential unexpected findings.

A case of rectal cancer in a patient with neurofibromatosis type 1

A rectal cancer was found in a 67-year-old man with a history of neurofibromatosis type 1. A low anterior resection was performed, and he received concurrent chemoradiation for 6 months. Twelve months after the surgery, a tumor was found at the anastomotic site by positron emission tomography-computed tomography and colonoscopy and was mistaken as anastomotic site recurrence. The tumor was confirmed as an inflammatory myofibroblastic tumor through transanal excision.

Neurogenic tumors of soft tissue

Neurogenic tumors are an uncommon yet important category of soft tissue tumors in children and adolescents because of their frequent association with various genetic syndromes. The heterogeneous cellular composition of the peripheral nerve and the wide metaplastic capacity of the neural crest and its derivatives generate a variety of neoplasms with neurogenic differentiation. This article reviews the clinicopathologic features and differential diagnosis of neurogenic tumors in the first two decades of life, and highlights use of selected ancillary methods for diagnosis.

Recurrent retroperitoneal liposarcoma in a patient with neurofibromatosis type I

INTRODUCTION

Liposarcoma complicating neurofibromatosis is very rare. Only a few cases have been described until now. We present a case of recurrent dedifferentiated retroperitoneal liposarcoma in a patient with neurofibromatosis type I (NF-1).

CASE PRESENTATION

A 47-year-old Caucasian woman with NF-1 presented to the hospital initially complaining of left lumbar pain irradiating to the anterior thigh and knee. Physical examination showed atrophy of the lower extremities bilaterally and decreased motor strength on the left lower extremity. Radiological studies demonstrated an enhancing lesion in the left paraspinal region, suggesting malignancy. The patient underwent local resection of tumour with safety margins. Pathological examination was consistent with dedifferentiated liposarcoma (DDLS) with positivity for MDM2 and CDK4 markers. No evidence of metastasis was noted on the radiological studies. The final diagnosis was DDLS, high-grade (G3), pT2bN0M0, stage III. After 6 weeks post-tumour resection, the patient experienced recurrence of malignancy. Chemotherapy with cisplatin and doxorubicin was initiated in the patient.

CONCLUSIONS

Liposarcoma in the context of neurofibromatosis is very rare. To the best of our knowledge, only six cases have been reported until now in the literature. We are presenting this case to underline the possibility of recurrence in the case of retroperitoneal DDLSs despite local tumour resection. Also, although the role of chemotherapy is controversial we decided to start treatment with cisplatin and doxorubicin given the success of chemotherapy in similar case presentations.

Skewed allele-specific expression of the NF1 gene in normal subjects: a possible mechanism for phenotypic variability in neurofibromatosis type 1

Neurofibromatosis type 1 is an autosomal dominant disorder characterized by neurocutaneous abnormalities, learning disabilities, and attention-deficit disorder. Neurofibromatosis type 1 symptom severity can be highly variable even within families where all affected members carry the same mutation. We hypothesized that variation in the expression of the normal NF1 allele may be a mechanism that participates in producing variable phenotypes. We performed allelic expression imbalance assays on healthy control individuals to estimate the prevalence of skewed allelic expression of the NF1 gene. Approximately 30% of individuals in our sample population showed significant skewing of allelic expression away from the expected 50:50 ratio, indicating that differential regulation of the NF1 alleles occurs in a high proportion of individuals. Differences of up to 25% in allele-specific expression of the NF1 alleles were identified. In individuals with Neurofibromatosis type 1, who carry a mutant allele (haploinsufficient), this degree of expression skewing may be sufficient to modulate the phenotype.

Normal and abnormal development of the cerebellum and brainstem as depicted by diffusion tensor imaging

Diffusion tensor imaging (DTI) is an advanced MRI technique that measures the microscopic molecular motion of water to gain information about the brain structure. This modality and its application to fiber tractography have been increasingly used in the last years to study the neuroanatomical background of brain malformations. This article aims to give an overview of the application of DTI and fiber tractography on pediatric posterior fossa including malformations, acquired disorders affecting the white matter, and posterior fossa involvement in phacomatoses. For every disorder, we show the additional information that DTI and fiber tractography are providing compared to conventional MR sequences and discuss their significance. Additionally, we show at the beginning normal DTI and fiber tractography findings of the pediatric posterior fossa. Finally, we briefly discuss potential future uses for DTI and fiber tractography to further understand the pathogenesis of posterior fossa malformations and the neuronal plasticity and connectivity of acquired lesions affecting the posterior fossa.

Free flap reconstruction of extensive defects following resection of large neurofibromatosis

BACKGROUND

Neurofibromatosis type 1 (NF-1) is a locally invasive tumor that can grow extensively with diffuse infiltration into surrounding tissue. Resecting a large neurofibroma can result in an extensive defect that is difficult to reconstruct and can cause both aesthetic and functional deformities.

METHODS

From 2000 to 2010, 5 patients with NF-1 underwent radical resection and immediate reconstruction with 6 free flaps at our institution. All patients presented with recurrent tumor, and involved head and neck region in 4 and foot in 1 patient. Ages ranged from 18 to 75 years. The follow-up ranged from 1 to 94 months.

RESULTS

Defect sizes ranged from 84 to 252 cm. A single free flap was used in 4 cases and 2 free flaps were used in 1 case. All the flaps survived. Complications included loss of skin graft, necrosis of the distal tip of a flap, and wound dehiscence. All complications were successfully managed with minor surgical procedures.

CONCLUSION

Immediate reconstruction using a free flap after resecting a large neurofibroma is a safe and reliable method that facilitates radical resection of the tumors that are difficult to resect and that may result in an extensive defect.

Oncologic manifestations of neurofibromatosis type 1 in Korea

PURPOSE

The aim of this study was to investigate the incidence and spectrum of malignant tumors in Korean neurofibromatosis type 1 (NF1) patients.

METHODS

We retrospectively reviewed 125 patients who were diagnosed with NF1 at a single institution from 1995 to 2010. The incidence, location, histologic type, and radiologic findings of malignant tumors as well as development of multiple primary tumors were analyzed.

RESULTS

Eighteen malignant tumors occurred in 16 patients (12.8%) among 125 Korean NF1 patients; 9 carcinomas, 8 sarcomas and 1 central nervous system (CNS) tumor. Five tumors were of nervous system origin and 13 were non-nervous system tumors. The locations of the tumors were as follow: 1 CNS, 2 lung, 3 breast, 3 stomach, 3 small bowel, 1 colon, 1 liver, 1 uterus, 1 neck, and 2 in extremities. Three malignant peripheral nerve sheath tumors (MPNSTs) occurred at the neck and extremity, and one in the liver. All three gastrointestinal stromal tumors (GISTs) had multiple tumors in the jejunum, and one MPNST and one pheochromocytoma were accompanied in two GISTs. Multiple primary tumors, benign or malignant were reported in 4 patients (25.0%), synchronously or metachronously.

CONCLUSION

Korean NF1 patients had a high risk of developing malignant tumors. The common malignant tumors in Koreans such as breast, lung and stomach cancers developed frequently in addition to the NF1-related tumors such as MPNST or GIST.

Alternative splicing of the neurofibromatosis type I pre-mRNA

NF1 (neurofibromatosis type I) is a common genetic disease that affects one in 3500 individuals. The disease is completely penetrant but shows variable phenotypic expression in patients. NF1 is a large gene, and its pre-mRNA undergoes alternative splicing. The NF1 protein, neurofibromin, is involved in diverse signalling cascades. One of the best characterized functions of NF1 is its function as a Ras-GAP (GTPase-activating protein). NF1 exon 23a is an alternative exon that lies within the GAP-related domain of neurofibromin. This exon is predominantly included in most tissues, and it is skipped in CNS (central nervous system) neurons. The isoform in which exon 23a is skipped has 10 times higher Ras-GAP activity than the isoform in which exon 23a is included. Exon 23a inclusion is tightly regulated by at least three different families of RNA-binding proteins: CELF {CUG-BP (cytosine-uridine-guanine-binding protein) and ETR-3 [ELAV (embryonic lethal abnormal vision)-type RNA-binding protein]-like factor}, Hu and TIA-1 (T-cell intracellular antigen 1)/TIAR (T-cell intracellular antigen 1-related protein). The CELF and Hu proteins promote exon 23a skipping, while the TIA-1/TIAR proteins promote its inclusion. The widespread clinical variability that is observed among NF1 patients cannot be explained by NF1 mutations alone and it is believed that modifier genes may have a role in the variability. We suggest that the regulation of alternative splicing may act as a modifier to contribute to the variable expression in NF1 patients.

Genetic predisposition to peripheral nerve neoplasia: diagnostic criteria and pathogenesis of neurofibromatoses, Carney complex, and related syndromes

Neoplasms of the peripheral nerve sheath represent essential clinical manifestations of the syndromes known as the neurofibromatoses. Although involvement of multiple organ systems, including skin, central nervous system, and skeleton, may also be conspicuous, peripheral nerve neoplasia is often the most important and frequent cause of morbidity in these patients. Clinical characteristics of neurofibromatosis type 1 (NF1) and neurofibromatosis type 2 (NF2) have been extensively described and studied during the last century, and the identification of mutations in the NF1 and NF2 genes by contemporary molecular techniques have created a separate multidisciplinary field in genetic medicine. In schwannomatosis, the most recent addition to the neurofibromatosis group, peripheral nervous system involvement is the exclusive (or almost exclusive) clinical manifestation. Although the majority of cases of schwannomatosis are sporadic, approximately one-third occur in families and a subset of these has recently been associated with germline mutations in the tumor suppressor gene SMARCB1/INI1. Other curious syndromes that involve the peripheral nervous system are associated with predominant endocrine manifestations, and include Carney complex and MEN2b, secondary to inactivating mutations in the PRKAR1A gene in a subset, and activating mutations in RET, respectively. In this review, we provide a concise update on the diagnostic criteria, pathology and molecular pathogenesis of these enigmatic syndromes in relation to peripheral nerve sheath neoplasia.

A case of persistent foot pain in a neurofibromatosis type I patient

Introduction. This is the case of a young male patient who presented to his family physician with atypical left foot pain, which was extremely resistant to analgesia and caused significant disability. Despite extensive investigations, the cause of his pain was not identified until 18 months after his initial symptoms, when the official diagnosis of malignant peripheral nerve sheath tumour (MPNST) was made. Detailed review of the patient's past history established the diagnosis of type I neurofibromatosis (NF-1), previously undetected. Discussion. NF-1 is an autosomal dominant genetic disorder caused by loss of function mutations of the NF1 gene in chromosome 17. Patients with this condition are at increased risk for developing MPNSTs which, however, are treatable only in early stages. Conclusion. Although monitoring NF-1 patients for the development of MPNSTs is common practice, the index of clinical suspicion in patients without an established NF-1 diagnosis is low. Any atypical pain in young adults should raise the possibility of this malignancy, and this case illustrates the fact that MPNSTs can be the first manifestation of NF-1 in patients previously undiagnosed with the disease.

The genetics of phaeochromocytoma: using clinical features to guide genetic testing

Phaeochromocytoma is a rare, usually benign, tumour predominantly managed by endocrinologists. Over the last decade, major advances have been made in understanding the molecular genetic basis of adrenal and extra-adrenal phaeochromocytoma (also referred to as adrenal phaeochromocytoma (aPCA) and extra-adrenal functional paraganglioma (eFPGL)). In contrast to the previously held belief that only 10% of cases had a genetic component, currently about one-third of all aPCA/eFPGL cases are thought to be attributable to germline mutations in at least nine genes (NF1, RET, SDHA, SDHB, SDHC, SDHD, TMEM127, MAX and VHL). Recognition of inherited cases of aPCA/eFPGL is critical for optimal patient management. Thus, the identification of a germline mutation can predict risks of malignancy, recurrent disease, associated non-chromaffin tumours and risks to other family members. Mutation carriers should be offered specific surveillance programmes (according to the relevant gene). In this review, we will describe the genetics of aPCA/eFPGL and strategies for genetic testing.

Neoplasms associated with germline and somatic NF1 gene mutations

INTRODUCTION

Neurofibromatosis 1 is a tumor predisposition genetic syndrome with autosomal dominant inheritance and virtually 100% penetrance by the age of 5 years. NF1 results from a loss-of-function mutation in the NF1 gene, resulting in decreased levels of neurofibromin in the cell. Neurofibromin is a negative regulator of various intracellular signaling pathways involved in the cellular proliferation. Although the loss of heterozygosity in the NF1 gene may predispose NF1 patients to certain malignancies, additional genetic alterations are a prerequisite for their development. The precise nature of these additional genetic alterations is not well defined, and genetic testing of all malignancies in NF1 patients becomes an essential component of future research in this subset of patients. In addition to germline NF1 mutations, alteration of the somatic NF1 gene is associated with sporadic malignancies such as adenocarcinoma of the colon, myelodysplastic syndrome, and anaplastic astrocytoma.

MATERIALS AND METHODS

A comprehensive English and non-English language search for all articles pertinent to malignancies associated with NF1 was conducted using PubMed, a search engine provided by the U.S. National Library of Medicine and the National Institutes of Health. Key words searched included the following: "malignancies associated with NF1", "tumors associated with NF1", and "NF1 and malignancies". A comprehensive analysis in terms age and mode of presentation, investigation and therapeutic modalities, and outcome of the published data was performed and compared with similar information on the sporadic cases.

RESULTS

Malignancies in NF1 patients typically occur at an earlier age and, with an exception of optic pathway gliomas, certain types of malignancies carry a poor prognosis compared with their sporadic counterparts. Malignancies are the leading cause of death in NF1 patients, resulting in a 10- to 15-year decreased life expectancy compared with the general population.

CONCLUSIONS

The lack of well-defined screening tests for early detection and the nonspecific clinical presentation contributes to a poorer outcome in malignancies associated with NF1. Small study group size, mixed patient population, and a lack of uniformity in reporting research results make comparison of treatment outcome for this group difficult. An International Consensus Meeting to address and recommend best practices for screening, diagnosis, management, and follow-up of malignancies associated with NF1 is needed.

Diffuse large B cell lymphoma presenting as Horner's syndrome in a patient diagnosed with neurofibromatosis type 1: a case report and review of the literature

Introduction

Horner's syndrome has a variety of etiologies ranging from benign to serious life-threatening conditions and has been infrequently reported as a presenting symptom of patients with lymphoid neoplasms. Only one case of Burkitt's lymphoma presenting with toothache, paresthesia, and Horner's syndrome has been described and no case reports of diffuse large B-cell lymphoma as the etiology of Horner's syndrome currently exist in the literature. In addition, lymphoid neoplasms have rarely been reported to occur in patients with neurofibromatosis type 1 despite an increased risk of many types of cancer in such cases.

Case presentation

A 28-year-old Thai man presented with a progressively enlarged left supraclavicular mass together with a significant weight loss and night sweating for four months. He also noticed hoarseness and ptosis of his left eye associated with double vision for two months. Physical examination revealed large supraclavicular lymphadenopathy and Horner's syndrome (ptosis, miosis, and anhydrosis) on the left side of his face. A large mediastinal mass was clearly detected by chest X-ray and computed tomography and subsequent lymph node biopsy provided a diagnosis of diffuse large B-cell lymphoma. Interestingly, the patient was also definitely diagnosed with neurofibromatosis type 1 from multiple café au lait macules, axillary freckles, three neurofibromas, multiple Lisch nodules, and a history of affected family members. He subsequently received chemotherapy with a good response. Twenty-seven cases of various types of lymphoid neoplasms previously reported to occur in neurofibromatosis type 1 patients were also extracted from the literature. All cases were non-Hodgkin lymphoma and the major subtype was T-cell. Only nine cases were B-cell lymphoma. The majority of cases were young with a median age at lymphoma diagnosis of 9.4 years (range 1.1 to 77 years). Two-thirds of the cases were boys or men. Other concomitant malignancies were brain tumor, colorectal cancer, pheochromocytoma, and acute lymphoblastic leukemia.

Conclusions

We describe for the first time a case of diffuse large B-cell lymphoma that occurred in a neurofibromatosis type 1 patient with Horner's syndrome. Horner's syndrome can be an initial manifestation of diffuse large B-cell lymphoma. Patients who present with a classical triad of Horner's syndrome should always be fully investigated for lymphomatous involvement, especially in the thorax. The exact molecular mechanism for diffuse large B-cell lymphoma development in neurofibromatosis type 1 cases remains to be elucidated.

[Unusual clinical manifestations of type 1 neurofibromatosis]

Type 1 neurofibromatosis is an autosomal dominant hamartosis caused by mutations of the neurofibromin-1 gene. The classic features of the clinical phenotype include the presence of café-au-lait spots, neurofibromas, axillary and inguinal freckling, Lisch-nodules and deformities of the skeletal system, as well as the risk of developing multiple tumors, especially in the central nervous system. However, it is known from the literature that the phenotypic variability can pose a huge diagnostic difficulty.

AIMS

Our institute performs molecular genetic testing of the neurofibromin-1 gene since 2008; during this period several unusual phenotypic variants were found.

RESULTS, CONCLUSION

The reported four cases represent interesting phenotypic variants or diagnostic challenges in which the final diagnosis was established by molecular genetic analysis.

Múltiplas hiperintensidades no sistema nervoso central em uma criança com neurofibromatose do tipo 1

OBJETIVO: Relatar o caso de uma criança com neurofibromatose do tipo 1, apresentando o achado ocasional de múltiplas hiperintensidades e de lesão hamartomatosa pré-quiasmática no sistema nervoso central. DESCRIÇÃO DO CASO: Menino de tez escura de quatro anos, cujo pai apresentava manchas café-com-leite e história de cirurgia de tumor de ouvido. A criança evoluiu com um adequado desenvolvimento neuropsicomotor, sem crises convulsivas ou déficit de aprendizagem. Ao exame físico, possuía múltiplas manchas café-com-leite e efélides. A avaliação pela ressonância nuclear magnética de encéfalo evidenciou múltiplas imagens nodulares hiperintensas em T2 e Flair, com isossinal em T1, localizadas na substância branca dos hemisférios cerebrais, cerebelo e tronco cerebral. Apresentava ainda lesão hamartomatosa pré-quiasmática. A avaliação eletroencefalográfica e o exame neurológico eram normais. COMENTÁRIOS: As imagens hiperintensas verificadas na ressonância nuclear magnética correspondem aos chamados unidentified bright objects (UBOs), observados em de 60 a 70% das crianças com neurofibromatose do tipo 1, sendo raros em adultos. Sua etiologia e significado clínico ainda não são claros. Alguns estudos os têm associado à disfunção cognitiva, déficit neurológico e risco de malignização. Hamartomas localizados próximos ao quiasma óptico são incomuns, mas podem se relacionar à puberdade precoce. A avaliação do sistema nervoso central de crianças assintomáticas com neurofibromatose do tipo 1 é discutível. Contudo, nos casos em que UBOs sejam identificados, é importante considerar seu seguimento radiológico, especialmente diante de lesões múltiplas ou atípicas.