Neurofibromatosis type 1

Neurofibromatosis 1 (NF1) is an autosomal dominant neurocutaneous disorder with an incidence of approximately 1 in 4000. Cognitive deficits and academic learning difficulties are the most common neurological 'complication' of NF1 in childhood and can be responsible for significant lifetime morbidity. The NF1 gene is usually classified as a tumor suppressor gene, but it is not yet known how NF1 gene mutations cause many of the non-tumor manifestations of the disorder. The NF1 protein, neurofibromin is expressed early during embryonic development with high levels of expression in the brain, suggesting that it plays an important role in regulating the orderly differentiation of central nervous system neurons. The mouse model for NF1 demonstrates behavioral abnormalities which bear striking similarity to the cognitive phenotype observed in humans with NF1. This review summarises our current understanding of the function of the NF1 gene, the nature of cognitive deficits in this disorder and correlations between neuroradiological, pathological and neuropsychological findings and animal studies which provide an insight into the pathogenesis.     

Neurofibromatosis type 1 and pregnancy

Neurofibromatosis Type 1 (NF-1) is an autosomal dominant condition which has markedly variable clinical expression, with manifestations ranging from mild cutaneous lesions to severe orthopedic complications and functional impairment. The current obstetrical literature indicates that women with NF-1 have increased complications associated with pregnancy. However, the majority of publications are case reports involving no more than 11 patients each, and are likely biased toward reporting on cases in which complications occurred. This study presents data on pregnancy outcome in 105 women with NF-1. The data were obtained from questionnaires completed by the study participants, and by review of their pregnancy and peripartum medical records. The 105 women had a total of 247 pregnancies, resulting in 182 live births, 44 first trimester spontaneous abortions, 21 elective terminations, and 2 ectopic pregnancies. There were two sets of twins. The cesarean section rate in our series (36%) was greater than the general population rate (9.1–23.5%). In 7 of these patients, the cesarean section was required because of maternal NF-1 complications. The study did not show the previously reported increased incidence of preeclampsia, preterm delivery, intrauterine growth restriction, pregnancy-induced hypertension, stillbirth, spontaneous abortion, or perinatal mortality. Sixty-four (60%) of the one hundred five women reported growth of new neurofibromas during pregnancy and fifty-five (52%) noted enlargement of existing neurofibromas. Nineteen women observed no changes in the size of their neurofibromas and no growth of new neurofibromas during pregnancy. © 1996 Wiley-Liss, Inc.     

Neurofibromatosis type 1 and malignancy in childhood

Neurofibromatosis type 1 (NF1) is an autosomal dominant hereditary neurocutaneous syndrome characterized by multi‐system involvement and an increased incidence of both benign and malignant tumors. In this study, we evaluated the clinical presentation and prognosis of NF1 and malignancy. Between 1975 and 2013, 26 (5%) of the 473 patients with NF1 at our center developed non‐neurofibroma neoplasms. The patient files of 26 subjects with tumors, other than optic glioma, were analyzed retrospectively to evaluate clinical features and treatment results. The age at diagnosis of NF1 ranged from 3 months to 16 years (median 5.5 years). The age range at tumor diagnosis was 1.5–33 years (median 8 years) in these 26 patients. The tumor histological subtypes included the following: 12 soft‐tissue tumors (6 malignant peripheral nerve sheath tumors (MPNST), 5 rhabdomyosarcomas (RMS) and 1 malignant fibrous histiocytoma), 11 brain tumors (6 low‐grade gliomas, 3 high‐grade gliomas, and 2 medulloblastoma), 2 neuroblastomas and 1 non‐Hodgkin's lymphoma. Twelve of 26 patients were alive at the time of the study. Although benign brain tumors with NF1 are more common, high‐grade brain tumors also occur. Thus, careful and regular follow‐up is crucial for early detection of malignancy in NF1 patients.     

Neurofibromatosis type 2

Neurofibromatosis type 2 is an often devastating autosomal dominant disorder which, until relatively recently, was confused with its more common namesake neurofibromatosis type 1. Subjects who inherit a mutated allele of the NF2 gene inevitably develop schwannomas, affecting particularly the superior vestibular branch of the 8th cranial nerve, usually bilaterally. Meningiomas and other benign central nervous system tumours such as ependymomas are other common features. Much of the morbidity from these tumours results from their treatment. It is now possible to identify the NF2 mutation in most families, although about 20% of apparently sporadic cases are actually mosaic for their mutation. As a classical tumour suppressor, inactivation of the NF2 gene product, merlin/schwannomin, leads to the development of both NF2 associated and sporadic tumours. Merlin/schwannomin associates with proteins at the cell cytoskeleton near the plasma membrane and it inhibits cell proliferation, adhesion, and migration.     

Neuropsychological impairments in elderly Neurofibromatosis type 1 patients

Cognitive performance is compromised in Neurofibromatosis type 1 (NF1) patients, but neuropsychological data including elderly NF1 are extremely sparse. We compared the cognitive performance of a small elderly NF1 group (n = 5) with an age-matched healthy control group (n = 49). NF1 group performed worse than control group on a global cognitive impairment task, verbal working memory, and visuospatial functioning. The results suggest that cognitive impairment is an important feature of NF1 across lifespan, including elderly individuals. Future studies approaching the NF1 cognitive profile might benefit from looking at the mechanisms linked to the age-related aspects of cognitive decline.     

Neurofibromatosis type 1: from genotype to phenotype

Although neurofibromatosis 1 (NF1) is a common Mendelian disorder with autosomal-dominant inheritance, its expression is highly variable and unpredictable. Many NF1 patients have been genotyped but few allele-phenotype correlations have been identified. NF1 genotype-phenotype correlations are difficult to identify because of the complexity of the NF1 phenotype, its strong age dependency, the relatedness of many clinical features and the huge heterogeneity of pathogenic NF1 mutations. Some NF1 patients with a given NF1 mutation may develop very severe disease while others with the same mutation have only mild symptoms. This phenotypic variability may be due to both modifier genes and environmental factors. Recent targeted strategies have identified several interesting candidate modifier genes.     

Neurofibromatosis type 1 of the child increases birth weight

Neurofibromatosis type 1 (NF1) is associated with reduced adult height, but there are no cohort studies on birth size. This retrospective study includes a cohort of 1,410 persons with NF1 and a matched comparison cohort from the general population. Figures for birth size were retrieved from the administrative registers of Finland, and the data were converted to standard deviation scores (SDS), defined as standard deviation difference to the reference population. The birth weight among infants with NF1 was higher than among infants without the disorder (adjusted mean difference [95% confidence interval]: 0.53 SDS [0.19–0.87]), as was the head circumference at birth (0.58 SDS [0.26–0.90]). The birth length of the NF1 infants did not differ significantly from the comparison cohort. The birth weight in the group consisting of NF1 and non‐NF1 infants of NF1 mothers was lower than among infants of mothers in the comparison cohort (?0.28 SDS [?0.51 to ?0.06]), as was the birth length (?0.22 SDS [?0.45 to 0.00]). In conclusion, the birth weight and head circumference of persons with NF1 are significantly higher than those of persons without the disorder. NF1 of the mother reduces birth weight and birth length of the infant.     

Early-onset stroke in two siblings with Neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is an autosomal dominant neurocutaneous disorder, characterized by cafe-au-lait macules, benign neurofibromas as well as malignant peripheral nerve sheath tumours, freckling in the axillary or inguinal regions, optic glioma and Lisch nodules (iris hamartomas) and further manifestations like bone deformities etc.Additionally, NF1 patients are at increased risk of early-onset cerebrovascular diseases, the pathogenesis of which has not been clarified yet.Here we report the first case of two siblings with NF1 who suffered an acute ischemic stroke.Professionals treating NF1 patients should be aware of the elevated risk of stroke in this population. Large prospective studies are needed to establish optimal guidelines for diagnosis, monitoring and treatment of cerebrovascular disease in patients suffering from NF1, as well as to achieve a consensus on routine vascular screening in NF1.     

Neurofibromatosis 1

Neurofibromatosis 1 predisposes affected individuals to the development of benign and malignant tumours that are frequently disfiguring and difficult to manage. However, advances in molecular biology and the development of mouse models have facilitated our understanding of disease pathogenesis. Positron emission tomography has demonstrated that sophisticated imaging techniques have a role in diagnosing complex problems like malignant peripheral nerve sheath tumours, while the prospect of targeted therapies for Nf1 complications is tantalisingly close.     

Neurofibromatosis type 1 in Israel: survey of young adults.

Neurofibromatosis type 1 (NF1) (von Recklinghausen's disease) is one of the most common human autosomal dominant disorders. In a survey of 374440 17 year old Jewish recruits for military service, 390 cases of NF1 were discovered, with a prevalence of 1.04/1000 (0.94/1000 for males and 1.19/1000 for females), or two to five times the reported prevalence of this disease. NF1 was more common in youngsters whose parents were of North African and Asian origin (1.81/1000 and 0.95/1000, respectively) and less common in those of European and North American origin (0.64/1000). All these differences were statistically significant and may be partially explained by the more advanced parental age of the NF group (as suggested by the larger number of children in the North African and Asian families) or by founder effect or both. The height and weight of the NF1 subjects was significantly lower than those of the controls. The intelligence score of persons with NF1 was similar to that of the control group when corrected for gender and ethnic origin. No significant increase in epilepsy or mental illnesses was found. This study provides evidence of the high overall prevalence of NF1 among Jews in Israel, with significantly increased prevalence in certain ethnic groups.     

Neurofibromatosis type 1-associated unusual pleomorphic astrocytoma displaying continual malignant progression

Patients with neurofibromatosis type 1 (NF1) often have gliomas as a complication, most of which are benign pilocytic astrocytomas which have arisen in optic pathways. In the present case, a 17-year-old girl (at death) with stigmata of NF1, initially had a bulky tumor mass in the left thalamus, developing into the lateral ventricle, at 13 years of age. Partially resected tissue samples showed pleomorphic astrocytoma with abundant xanthoma cells and degenerative structures such as Rosenthal fibers (RF) and eosinophilic granular bodies. Fine eosinophilic granules identical to RF, both immunophenotypically and ultrastructurally, were also seen. The residual tumor was subtotally resected 6 months later, and the tumor histology was essentially similar as before, accompanying the regenerative structures; this was believed to be a good prognostic indicator. However, several anaplastic features such as mitosis, necrosis and vascular proliferation appeared even in areas rich in the regenerative structures. After a 2-year, disease-free interval, multiple tumor relapse occurred in June 1997. Partially resected tumor tissues were composed of monotonous small anaplastic cells with prominent proliferative activity. Surprisingly, the tumor cells had retained eosinophilic granules within the cell bodies. Postoperative chemotherapy with procarbazine, MCNU and vincristine (PCV) suppressed the residual tumor dramatically, but the regrowing tumor finally became uncontrollable, leading to the patient's death. TP53 mutation was not detected, while p27 immunopositivity was constantly high during malignant progression, suggesting acquisition of proliferative activity to overcome p53 and p27 inhibitory functions. A review of previously published reports failed to reveal any cases of this type.     

Lovastatin regulates brain spontaneous low-frequency brain activity in Neurofibromatosis type 1

In the Neurofibromatosis type 1 (NF1) mouse model, lovastatin, used clinically for hypercholesterolemia, improves cognitive dysfunction. While such impairment has been studied in NF1, the neural substrates remain unclear. The aim of this imaging add-on to a Phase 1 open-label trial was to examine the effect of lovastatin on Default Network (DN) resting state functional connectivity (RSFC). Seven children with NF1 (aged 11.9 ± 2.2; 1 female) were treated with lovastatin once daily for 12 weeks. A 7-min 3-T echo-planar-imaging scan was collected one day before beginning treatment (off-drug) and the last day of treatment (on-drug) while performing a flanker task. After regressing-out task-associated variance, we used the residual time series as "continuous resting-state data" for RSFC analyses using 11 DN regions of interest. For qualitative comparisons, we included a group of 19 typically developing children (TDC) collected elsewhere. In the on-drug condition, lovastatin increased long-range positive RSFC within DN core regions (i.e., anterior medial prefrontal cortex and posterior cingulate cortex, PCC). In addition, lovastatin produced less diffuse local RSFC in the dorsomedial prefrontal cortex and PCC. The pattern of RSFC observed in the NF1 participants when on-drug closely resembled the RSFC patterns exhibited by the TDC. Lovastatin administration in this open trial regulated anterior-posterior long-range and local RSFC within the DN. These preliminary results are consistent with a role for lovastatin in normalization of developmental processes and with apparent benefits in a mouse NF1 model.     

Neurofibromatosis type 1 in two siblings due to maternal germline mosaicism

Neurofibromatosis type 1 (NF1) is caused by loss of function mutations of the NF1 gene, which are de novo in 50% of cases. Although this gene shows one of the highest mutation rates in the human genome, germline mosaicism is very rare in this condition. We describe the molecular analysis of a family in which neurofibromatosis type 1 occurred in two out of four siblings born to unaffected parents. Molecular analysis of the NF1 gene identified in both patients the same splicing mutation c.1392+1G>A, which was absent in parental lymphocytes. Microsatellite analysis showed that the two affected siblings shared the same maternal allele, however a specific PCR‐RFLP assay excluded the presence of the NF1 splicing mutation in multiple maternal tissues. Our molecular and clinical findings are consistent with a germline mosaicism for the NF1 splicing mutation. This is the first case of maternal germline mosaicism for a NF1 mutation characterized so far at the molecular level. Our data confirm that germline mosaicism is rare in neurofibromatosis 1, but it has important implications for genetic counseling.     

Neurofibromatosis type 1 gene product (neurofibromin) associates with microtubules

The neurofibromatosis type 1 (NF1) gene was recently identified by positional cloning and found to encode a protein with structural and functional homology to mammalian and yeast GTPase-activating proteins (GAPs). Using antibodies directed against the NF1 gene product, a protein of 250kDa was identified and termed neurofibromin. Double-indirect immunofluorescent labeling with anti-neurofibromin and anti-tubulin antibodies demonstrates that neurofibromin associates with cytoplasmic microtubules. Immunoblotting of microtubule-enriched cytoplasmic fractions, using antibodies generated against neurofibromin, shows that neurofibromin copurifies with microtubules. When portions of neurofibromin are expressed in Sf9 insect cells they associate with polymerized microtubules; furthermore, the critical residues for this interaction reside within the GAP-related domain of neurofibromin. The unexpected association of neurofibromin with microtubules suggests that neurofibromin is involved in microtubule-mediated intracellullar signal transduction pathways.     

Neurofibromatosis/Noonan phenotype: a variable feature of type 1 neurofibromatosis

Since January 1989 we have ascertained patients with neurofibromatosis type 1 (NFl) as part of our genetic register in the North West of England. This register has now identified 453 affected cases from 235 families. The first 94 individuals were specifically examined for features of the Noonan phenotype. This was present in 12/94 sequentially identified individuals with NFl, including six individuals from three families. However, three cases occurred in a further family, where Noonan syndrome appeared to segregate separately from NFl. We have provided evidence for the chance association of Noonan syndrome and NFl and that the Noonan phenotype occurs as a feature in some NFl families. However, there is now little evidence of a separate NFl/Noonan syndrome entity or of NFl features occurring in classical Noonan syndrome.     

Ⅰ型神经纤维瘤一家系4例的分析报告

目的 分析一个面部有巨大神经纤维瘤家系的临床表现及遗传方式.方法 根据美国国立卫生研究院(NIH)提出的神经纤维瘤诊断标准进行诊断,通过染色体检查和家系分析方法确定遗传方式.结果 家系12名成员中有3名患者表现出Ⅰ型神经纤维瘤的4项临床特征,染色体检查无异常,家系分析表现出常染色体显性遗传特点.结论 该家系为Ⅰ型神经纤维瘤家系,遗传方式为常染色体显性遗传.     

Neurofibromatosis 1 and 2

Neurofibromatosis (NF) 1 and 2 are multisystem disorders associated with a variety of neoplastic and non-neoplastic manifestations that typically progress in severity during the lifetime of the affected patient. The importance of appropriately diagnosing these disorders stems from the fact that the natural history of an associated neoplasm, such as a peripheral nerve tumor or an optic glioma, may be significantly different depending on whether or not the lesion arises in a person with NF. In addition, the indications for therapeutic intervention, hierarchy of treatment options and long-term management goals may differ substantially for patients with NF-related versus sporadic tumors. Finally, recognition of the diagnosis comprises an essential step for providing appropriate multidisciplinary evaluation and counseling to affected patients and their families. This article addresses the principal manifestations of these disorders and provides a contemporary review of the diagnostic and therapeutic issues that arise in children with NF1 and NF2.     

Neurofibromatosis type 1‐related pseudarthrosis: Beyond the pseudarthrosis site

Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder affecting approximately 1 in 2,000 newborns. Up to 5% of NF1 patients suffer from pseudarthrosis of a long bone (NF1‐PA). Current treatments are often unsatisfactory, potentially leading to amputation. To gain more insight into the pathogenesis we cultured cells from PA tissue and normal‐appearing periosteum of the affected bone for NF1 mutation analysis. PA cells were available from 13 individuals with NF1. Biallelic NF1 inactivation was identified in all investigated PA cells obtained during the first surgery. Three of five cases sampled during a later intervention showed biallelic NF1 inactivation. Also, in three individuals, we examined periosteum‐derived cells from normal‐appearing periosteum proximal and distal to the PA. We identified the same biallelic NF1 inactivation in the periosteal cells outside the PA region. These results indicate that NF1 inactivation is required but not sufficient for the development of NF1‐PA. We observed that late‐onset NF1‐PA occurs and is not always preceded by congenital bowing. Furthermore, the failure to identify biallelic inactivation in two of five later interventions and one reintervention with a known somatic mutation indicates that NF1‐PA can persist after the removal of most NF1 negative cells.