Features Of Neurofibromatosis Type Research Articles

Genetic basis and imaging findings of neurofibromatosis 1 and other somatic overgrowth disorders.

Somatic overgrowth disorders comprise a wide range of rare conditions that present with focal enlargement of one or more tissue types. The PI3K-AKT-mTOR pathway is a signalling pathway that induces angiogenesis and cell proliferation, and is one of the most commonly overactivated signalling pathways in cancer. The PI3K-AKT-mTOR pathway can be up-regulated by genetic variants that code for proteins in this pathway, or down-regulated by proteins that inhibit the pathway. Mosaic genetic variations can result in cells that proliferate excessively in specific anatomical locations. The PIK3CA-related overgrowth spectrum (PROS) disorders include CLOVES syndrome, macrodystrophia lipomatosa, and Klippel-Trenaunay syndrome among many. The neurofibromatosis type 1 (NF1) gene encodes neurofibromin which down-regulates the PI3K-AKT-mTOR pathway. Thousands of pathological variants in the NF1 gene have been described which can result in lower-than-normal levels of neurofibromin and therefore up-regulation of the PI3K-AKT-mTOR pathway promoting cellular overgrowth. Somatic overgrowth is a rare presentation in NF1 with a wide range of clinical and radiological presentations. Hypertrophy of all ectodermal and mesodermal elements has been described in NF1 including bone, muscle, fat, nerve, lymphatics, arteries and veins, and skin. The shared signalling pathway for cellular overgrowth means that these radiological appearances can overlap with other conditions in the PIK3CA-related overgrowth spectrum. The aim of this review is to describe the genetic basis for the radiological features of NF1 and in particular compare the appearances of the somatic overgrowth disorders in NF1 with other conditions in the PIK3CA-related overgrowth spectrum.

Impact of neurofibromatosis type 1 on quality of life using the Skindex-29 questionnaire quality of life in NF1.

Neurofibromatosis type 1 (NF1) is one of the most common RASopathies predisposing affected patients to melanic lesions and benign tumors. NF1 is associated with considerable esthetic and functional burden negatively affecting the patient's quality of life (QoL). This study aims to assess the clinical features of NF1 patients and evaluate their impact on QoL. We identified NF1 patients from a public health database of a region in Spain. All patients underwent clinical and ophthalmological evaluation for NF1 features. We measured QoL using the Spanish version of the Skindex-29. Forty patients fulfilled the NF1 National Institute of Health criteria when we recruited patients. The median age was 42.00 years (IQR 26.5 -53.75). The median total Skindex-29 score was 12.3 (IQR 5.9-22.4); (emotion: 15.0, IQR 5.0-37.5; symptoms 8.9, IQR 0.0-17.9 and functioning 8.3; IQR 0.5-18.3). Women and NF1 patients with lower educational levels were associated with poorer QoL scores. We identified itching and sleep troubles to influence NF1 patients' QoL negatively. NF1 considerably influences the psychological well-being of NF1 patients. We observed that female and low-educated patients scored higher on the emotional dimension of the Skindex-29 and could, therefore, be more at risk of depression. We also pointed out some "minor symptoms" that negatively impact NF1 patients' QoL such, as itching and sleep troubles which doctors could treat if sought by doctors.

Spontaneous pseudoaneurysm of the superficial temporal artery in neurofibromatosis type 1: illustrative case.

A pseudoaneurysm of the superficial temporal artery is an uncommon clinical entity that has largely been linked with direct traumatic causes. Neurofibromatosis type 1 (NF1)-related vasculopathy is a rare cause of idiopathic arterial bleeding in the craniofacial region. A 46-year-old male with clinical features of NF1 presented to the hospital with an enlarging and tender right temporal mass without a history of trauma. Computed tomography angiography suggested the development of a pseudoaneurysm, and surgery was performed to resect the mass. Histopathological examinations showed focal interruption of the epithelium layer and elastic lamina, well-demarcated thickening of the smooth muscle layers of the arterial wall, supporting the diagnosis of pseudoaneurysm. NF1-associated vasculopathy is likely the predisposing factor for the development of a superficial temporal artery pseudoaneurysm.

Neurofibromatosis type 1 presenting as buphthalmos at birth and developing into dural herniation over a period of seven years

Neurofibromatosis type 1 (NF1) is a genetic disorder that is characterized by appearance of benign tumors of the nerves, soft tissues, and the skin. We discuss a case of a newborn who presented with buphthalmos in the left eye and who, over the years, developed all the features of NF1. There was progressive proptosis, plexiform-neurofibroma of the eyelid, café-au-lait spots, and pigmentation along the trigeminal nerve. There was absent left sphenoid bone–associated dural herniation into orbital spaces, as detected on MRI. Keeping neurofibromatosis as an etiological differential in patients presenting with buphthalmos can help treating physicians understand the spectrum of the approaching disease and counsel the parents accordingly.

Eating disorders in young patients with neurofibromatosis type 1.

We describe the association of neurofibromatosis type 1 (NF1) and feeding and eating disorders (FED) in five patients admitted to our third level centre for both FED and NF1. Case series of five adolescent females with NF1 treated for FED. We collected data from five patients with NF1 aged between 14 and 22 years, all females. The onset of eating disorder symptoms occurred between 13 and 19 years of age and was characterised by food intake restriction, associated with physical hyperactivity in three out of five cases. One patient also reported self-injurious acts and episodic binges. Patients received diagnoses of anorexia nervosa (AN, n=2), atypical AN (n=1), bulimia nervosa (n=1), unspecified feedingandeating disorder (n=1). The current literature reports a single case of an adult with NF1 and comorbid AN, focusing on the dermatological features of NF1. Our article describes a case series of five patients in developmental age affected by NF1 and FED. Clinical and psychological features of NF1 may play a role in the pathogenesis of FED when these two conditions co-occur. The dermatological alterations of NF1 may contribute to body image distortion that characterises AN. Further research is required to systematically screen populations of patients with NF1 for the presence of FED.

Abstract 12

Background: Neurofibromatosis type 1 (NF1) is a common dominant inherited disorder with highly variable expressivity. The highly variable clinical features of NF1 are because of there are many genetic modifiers that lie outside the NF1 gene, which influence NF 1 gene and account for a large fraction of the symptomatic variability seen in NF1. Mutation detection in the NF1 gene is complex due to its large size, the existence of several pseudo genes and the lack of clustering of the mutations. There are no clear mutation hotspots and the spectrum of mutations is very diverse, ranging from micro deletions affecting the entire NF1 gene to minor lesions that include a high proportion of splicing mutations. Objective: Identification of the genetic mutation in mother son duo with neurofibromatosis. Method: Whole exome analysis was performed to identify the genetic defect. The variants were prioritized using standard open-source computational pipelines. Results: Whole exome sequencing and computational analysis identified a novel missense (c.4244A>G) at 17q11.2 cytogenetic location of NF 1 gene. Despite having the same genetic variant, absence ofpheochromocytoma in mother indicates heterogeneous presentation of neurofibromatosis type 1. Conclusion: To the best of our knowledge, this is the first report describing neurofibromatosis due to novel frameshift ANOS1 gene mutations. The report also exemplifies poor correlation of genotype and phenotype in neurofibromatosis cases.

Neuroblastic tumors and neurofibromatosis type 1: A retrospective multicenter study in Italy and systematic review of the literature.

Neuroblastic tumors (NBTs) are the most common extra-cranial solid tumors of childhood. Neurofibromatosis type 1 (NF1) is the most common neurocutaneous disorder with a predisposition to tumors. The co-occurrence of NBTs in the setting of NF1 has been occasionally reported, suggesting a non-casual association and likely configuring a spectrum of neural crest-derived disorders. To explore the occurrence of NBTs within NF1 and to report on its natural history, therapeutic strategies, and outcomes in an Italian cohort of children with NF1 and in the literature. Study (a): a retrospective analysis of questionnaire-based data [years 1979-2017] derived from the databases of the Italian Registry for Neuroblastoma (RINB) of the Italian Society of Pediatric Onco-Haematology (AIEOP); and Study (b): a systematic review search on NF1/NB co-occurrence. Study (a) identified eight children with NBTs, 0.2% of patients registered in the RINB, fulfilling the diagnostic criteria for NF1. The primary site of NBTs was abdominal in six patients. The NBTs were neuroblastoma (NB) in five patients, ganglioneuroblastoma (GNB) in one, patient, and ganglioneuroma (GN) in two. Metastatic diffusion occurred in three out of eight children. MYCN gene testing, performed in the tumors of five patients, resulted not-amplified. The major features of NF1 included the following: NF1 family history in four patients, café-au-lait spots in all, freckling in six, Lisch nodules in three, and neurofibromas in three. With regard to the outcome, four children survived three of these for the progression of NB and one for a second tumor. Study (b) identified 12 patients with NF1/NB from the years 1966-2017, and the median age at diagnosis was 27 months (range = 0-168 months). The primary site of NB was thoracic. The prevalent histotype was NB in nine patients, GNB in two, and GN in one. Eight/nine NBs were metastatic. The MYCN gene was amplified in the only studied case. The NF1 features included NF1 family history in seven patients; the major NF1 features were café-au-lait spots in nine patients, freckling in one, Lisch nodules in none, and neurofibromas in six. The outcome was good for only two children, while eight children died of neuroblastoma, at a median age of 49.5 months (range = 2.4-174 months), with a median survival time of 21.75 months after diagnosis. To our knowledge, this represents the first systematic study on the occurrence of NBTs in NF1. This confirms that NBs are rare per se in the setting of NF1 (0.2% of all NBs) and even if compared to the overall frequency of malignancies in NF1 (i.e., 14.7%). The male:female ratio in study (a) (0.6) was different from what was recorded in study (b) (1.5) and in line with the overall increased frequency of malignancies in females with NF1. The median ages at diagnosis of NB in either study (a) or (b) were concordant with what occurred in the NB population. In study (a) versus study (b), the frequency of metastatic diffusion was lower, likely indicating less awareness on work-ups for malignancies in old NF1 series in the literature. The outcome was much better in study (a) than in study (b), indicating that multidisciplinary treatment for NB is highly recommended.

Neurofibromatosis from Head to Toe: What the Radiologist Needs to Know.

Neurofibromatosis type 1 (NF1) and neurofibromatosis type 2 (NF2) are autosomal dominant inherited neurocutaneous disorders or phakomatoses secondary to mutations in the NF1 and NF2 tumor suppressor genes, respectively. Although they share a common name, NF1 and NF2 are distinct disorders with a wide range of multisystem manifestations that include benign and malignant tumors. Imaging plays an essential role in diagnosis, surveillance, and management of individuals with NF1 and NF2. Therefore, it is crucial for radiologists to be familiar with the imaging features of NF1 and NF2 to allow prompt diagnosis and appropriate management. Key manifestations of NF1 include café-au-lait macules, axillary or inguinal freckling, neurofibromas or plexiform neurofibromas, optic pathway gliomas, Lisch nodules, and osseous lesions such as sphenoid dysplasia, all of which are considered diagnostic features of NF1. Other manifestations include focal areas of signal intensity in the brain, low-grade gliomas, interstitial lung disease, various abdominopelvic neoplasms, scoliosis, and vascular dysplasia. The various NF1-associated abdominopelvic neoplasms can be categorized by their cellular origin: neurogenic neoplasms, interstitial cells of Cajal neoplasms, neuroendocrine neoplasms, and embryonal neoplasms. Malignant peripheral nerve sheath tumors and intracranial tumors are the leading contributors to mortality in NF1. Classic manifestations of NF2 include schwannomas, meningiomas, and ependymomas. However, NF2 may have shared cutaneous manifestations with NF1. Lifelong multidisciplinary management is critical for patients with either disease. The authors highlight the genetics and molecular pathogenesis, clinical and pathologic features, imaging manifestations, and multidisciplinary management and surveillance of NF1 and NF2. Online supplemental material is available for this article. ©RSNA, 2022.

Clinical characteristics and genetic testing outcome of suspected hereditary peripheral nerve sheath tumours in a tertiary cancer institution in Singapore

BackgroundPeripheral Nerve Sheath Tumors (PNST) are a diverse group of mostly benign tumours uncommon in the general population. About 5–10% of PNSTs are hereditary, predominantly arising from germline variants in NF1, NF2, SMARCB1, or LZTR1 gene.MethodsWe reviewed the clinical characteristics and genetic testing results of patients referred to the NCIS Adult Cancer Genetics Clinic for suspected hereditary PNST.Results3,001 patients suspected to have various hereditary cancer syndromes were evaluated between year 2000 to March 2021. 13 (0.4%) were clinically diagnosed to have hereditary PNSTs. The majority were male (54%), with a median age at presentation to the genetics clinic of 29 years (range 19–48). 11/13 (85%) patients had multiple PNSTs, 12/13 (92%) had young onset PNSTs, 5/13 (38.5%) had personal and family history of PNST. 11/13 patients (85%) had clinical features of neurofibromatosis type 1 (NF1) including one patient who also fulfilled clinical criteria of neurofibromatosis type 2 (NF2); 2/13 (14%) had multiple schwannomas. Four patients underwent multi-gene panel testing, including one patient with clinical NF1, one patient who met both clinical NF1 and NF2 criteria, and two patients with multiple schwannomas. The patient with clinical features of NF1 was heterozygous for a pathogenic c. 2033dup variant in the NF1 gene. The patient with both NF1/NF2 features was heterozygous for a novel c.732 T > A nonsense variant in the NF2 gene. The two patients with multiple schwannomas were heterozygous for a pathogenic/likely pathogenic variant in the LZTR1 gene and are the first LZTR1-positive schwannomatosis patients reported in Asia.ConclusionHereditary PNSTs are rare referrals to an adult cancer genetics clinic. NF1 is the most common PNST seen. LZTR1 variants may be the underlying cause in Asian patients with multiple schwannomatosis.

Genetic testing to gain diagnostic clarity in neurofibromatosis type 2 and schwannomatosis.

Neurofibromatosis type 2 (NF2) and schwannomatosis (SWN) have distinct genetic etiologies but overlapping phenotypes. Genetic testing may be required for accurate diagnosis, which is critical for determining prognosis, screening recommendations, and treatment options. Our study aimed to compare the efficacy of germline-only versus paired (germline and tumor) genetic testing for clarifying the diagnosis in patients with features of NF2 and SWN. We performed a retrospective chart review of patients referred for NF2/SWN genetic testing at Massachusetts General Hospital from 2015 to 2020. Logistic regression analysis was performed to assess factors associated with diagnostic clarity. Overall, paired testing had 8.5 times greater odds of providing diagnostic clarity than germline-only testing (p < 0.01). Among patients who underwent paired testing, those who had analysis of two or more tumors had the greatest likelihood of gaining diagnostic clarity, with odds 13 times greater than patients who underwent germline-only testing (p < 0.01). Paired testing with analysis of one tumor significantly increased the odds of diagnostic clarity over germline-only testing by a factor of 6.5 (p < 0.01). These results have implications for genetic testing strategies and counseling patients about genetic testing utility. They also support the routine use of testing in individuals with suspected NF2 or SWN and improved insurance coverage for paired testing within this population.

A systematic review and meta-analysis of intellectual, neuropsychological, and psychoeducational functioning in neurofibromatosis type 1.

Neurofibromatosis Type 1 (NF1) is a common genetic disorder frequently associated with cognitive deficits. Despite cognitive deficits being a key feature of NF1, the profile of such impairments in NF1 has been shown to be heterogeneous. Thus, we sought to quantitatively synthesize the extant literature on cognitive functioning in NF1. A random-effects meta-analysis of cross-sectional studies was carried out comparing cognitive functioning of patients with NF1 to typically developing or unaffected sibling comparison subjects of all ages. Analyses included 50 articles (Total NNF1 = 1,522;MAge = 15.70 years, range=0.52-69.60), yielding 460 effect sizes. Overall moderate deficits were observed [g= -0.64, 95% CI=(-0.69, -0.60)] wherein impairments differed at the level of cognitive domain. Deficits ranged from large [general intelligence: g= -0.95, 95% CI=(-1.12, -0.79)] to small [emotion: g= -0.37, 95% CI=(-0.63, -0.11)]. Moderation analyses revealed nonsignificant contributions of age, sex, educational attainment, and parental level of education to outcomes. These results illustrate that cognitive impairments are diffuse and salient across the lifespan in NF1. Taken together, these results further demonstrate efforts should be made to evaluate and address cognitive morbidity in patients with NF1 in conjunction with existing best practices.

An unusual case of pediatric embryonal rhabdomyosarcoma with subsequent diagnosis of neurofibromatosis type 1

A 10-month-old girl presented with a 4-month history of a rapidly growing lesion on the lower lip. Initial assessment and Doppler ultrasound supported a diagnosis of pyogenic granuloma. However, emergent biopsy revealed an embryonal rhabdomyosarcoma, a highly malignant tumor commonly associated with cancer-susceptible syndromes including neurofibromatosis type 1 (NF1). Despite having no apparent clinical features of NF1 at initial presentation, she was later found to have multiple café-au-lait spots and a subsequent diagnosis of NF1 was made.

Case Report: Rare Case of NF2 in Pregnancy with Favorable Maternal and Perinatal Outcome, Under General Anesthesia Caesarean Section

Background: Neurofibromatosis type 2 (NF2) is an autosomal dominant disease due to chromosome 22 (22q12.2) mutation with a prevalence of 1:33,000-40,000. As many as 50% of cases are familial, 30-60% are genetic mosaic, de novo mutations. Tumor growth in NF often becomes more rapid in pregnancy. Pregnancy with NF2 has a risk of complications of hypertension, preeclampsia, cardiovascular problems, and IUGR (Intrauterine growth restriction). Case Reports: A 26-year-old woman, 29/30 weeks gestational age complaint of visual impairment, hearing loss, and multiple body masses. The results of MRI examination of the Head and whole Spine with contrast showed bilateral vestibular schwannoma, meningiomatosis, cervical schwannoma (C1-C5), which were features of NF2. Routine clinical evaluation, laboratory tests, fetal growth examination, and multidisciplinary management were performed during the antenatal care. There were no signs of increased intracranial pressure, hydrocephalus, and complications of preeclampsia, fetal abnormalities, or IUGR. A termination at 37 weeks of gestation with Caesarean Section and General Anesthesia was decided to reduce the increase of intracranial pressure during labor. A male infant was born with a birth weight of 2600 grams, without any abnormalities. Conclusion: Pregnancy in NF2 patient has a potential risk of tumor growth progression, preeclampsia, and IUGR, therefore it is necessary to monitor and evaluate the mother and fetus multidisciplinary during the pregnancy process to get good maternal and fetal outcomes. The mode of delivery in neurofibromatosis is determined mainly by obstetric indications.

A Rare Case Report of Neurofibromatosis Type 1 with Bladder Ganglioneuroma in a Paediatric Patient

Neurofibromatosis type 1 (NF1) is a rare Autosomal Dominant (AD) disease manifesting in paediatric age group with an incidence of 1/3500 births. It has a varied clinical presentation most commonly involving skin followed by the skeletal and central nervous systems. Genitourinary involvement is very rare. Peripheral neuroblastic tumours are classified into Neuroblastomas (NB), Ganglioneuroblastomas (GNB) and Ganglioneuromas (GN). They are classified according to their stage of maturation in a spectrum, which starts from NB, the most primitive form, and extends to GN, the most mature form. The authors hereby present a rare case report of a paediatric patient presenting with NF1 features and a bladder ganglioneuroma. The 11-year-old male child presented with a history of haematuria since two weeks accompanied with increased micturation frequency and nocturia. Neurocutaneous markers suggestive of a diagnosis of Neurofibromatosis type 1 were observed during clinical examination. Computed Tomography Intravenous Urogram (CT-IVU) revealed a large irregular pelvic mass involving the wall of the urinary bladder. Enlarged mesenteric lymph nodes were observed during exploratory laparotomy, frozen section bipopsy of which was reported as ganglioneuroma. Partial cystectomy was performed along with complete excision of the mass. Histopathological examination confirmed the diagnosis of bladder ganglioneuroma.

Double Head: Giant Solitary Occipital Scalp Plexiform Neurofibroma Without Neurofibromatosis

A 16-year-old male presented with solitary occipital plexiform neurofibroma, which had grown slowly over several years to reach giant size, thereby mimicking a "double head." There were no features of neurofibromatosis type 1. Total excision of the neurofibroma was done by infiltrating adrenaline circumferentially around the tumor before scalp incision. The feeding arteries were identified in the dense connective tissue above the aponeurosis and ligated or cauterized. Dissection was then carried out in the loose areolar tissue preserving the periosteal layer. There was no evidence of malignant transformation on histopathology, and 5-year follow-up showed no tumor recurrence.

Auditory Dysfunction Among Individuals With Neurofibromatosis Type 1

Neurofibromatosis type 1 (NF1) affects hearing through disruption of central auditory processing. The mechanisms, functional severity, and management implications are unclear. To investigate auditory neural dysfunction and its perceptual consequences in individuals with NF1. This case-control study included children and adults with NF1 and control participants matched on age, sex, and hearing level. Patients were recruited through specialist neurofibromatosis and neurogenetic outpatient clinics between April and September 2019. An evaluation of auditory neural activity, monaural/binaural processing, and functional hearing was conducted. Diffusion-weighted magnetic resonance imaging (MRI) data were collected from a subset of participants (10 children with NF1 and 10 matched control participants) and evaluated using a fixel-based analysis of apparent fiber density. Type and severity of auditory dysfunction evaluated via laboratory testing and questionnaire data. A total of 44 participants (18 [41%] female individuals) with NF1 with a mean (SD) age of 16.9 (10.7) years and 44 control participants (18 [41%] female individuals) with a mean (SD) age of 17.2 (10.2) years were included in the study. Overall, 11 participants (25%) with NF1 presented with evidence of auditory neural dysfunction, including absent, delayed, or low amplitude electrophysiological responses from the auditory nerve and/or brainstem, compared with 1 participant (2%) in the control group (odds ratio [OR], 13.03; 95% CI, 1.59-106.95). Furthermore, 14 participants (32%) with NF1 showed clinically abnormal speech perception in background noise compared with 1 participant (2%) in the control group (OR, 20.07; 95% CI, 2.50-160.89). Analysis of diffusion-weighted MRI data of participants with NF1 showed significantly lower apparent fiber density within the ascending auditory brainstem pathways. The regions identified corresponded to the neural dysfunction measured using electrophysiological assessment. The findings of this case-control study could represent new neurobiological and clinical features of NF1. Auditory dysfunction severe enough to impede developmental progress in children and restrict communication in older participants is a common neurobiological feature of the disorder.

Schwannomatosis of the tibial nerve

&lt;p class="abstract"&gt;Schwannoma is the most common type of benign tumor arising from the sheaths of the peripheral nerves. It occurs as a solitary tumor in most cases, but when it appears in multiple forms, it is necessary to differentiate it from plexiform schwannoma, schwannomatosis, neurofibroma and malignant peripheral nerve tumors. The authors experienced schwannomatosis in the tibial nerve without the features of neurofibromatosis type 2, so here we present a case report and literature review.&lt;/p&gt;

Analysis of the features of neurofibromatosis type 1 in the Republic of Bashkortostan

Neurofibromatosis type 1 (NF1) is an autosomal dominant hereditary tumor syndrome that occurs on average with a frequency of 1: 3000 people. Clinical features of NF1 include cafe-au-lait macules on the skin, multiple cutaneous, subcutaneous, and plexi-form neurofibromas, Lisch nodules, and optic gliomas. The disease is also characterized by damage to the musculoskeletal system, impaired intelligence and behavior. The cause of the disease is germinal mutations in the NF1 gene, which encodes the oncosuppressor neurofibromin. NF1 is characterized by pronounced polymorphism of clinical manifestations, from erased to severe, without geno-phenotypic correlations. Therefore, the role of modifier genes in the pathogenesis of NF1 is assumed. We carried out a clinical-epidemiological and molecular-genetic study of patients with NF1 from the Republic of Bashkortostan (RB). We searched for intragenic mutations by sequencing 57 exons of the NF1 gene, and identified deletions of the entire gene using microsatellite analysis. The prevalence of NF1 in RB is 10 per 100 000. We identified 14 intragenic mutations in the NF1 gene in 20 patients with NF1 and 2 extended deletion of NF1 gene in 3 patients from 2 unrelated families. We did not find a correlation between the type of mutation and the characteristics of the clinical manifestations of the disease. To determine the possible influence of modifier genes on pathogenesis of NF1, we carried out a comparative analysis of the clinical manifestations of NF1 depending on inheritance, ethnicity and association of systemic manifestations. Among the clinical manifestations of NF1 in RB, there was a low frequency of optic nerve gliomas (5,25%) and plexiform neurofibromas (5%). The incidence of brain cysts was 4,25% among patients with NF1. We identified 9 mutations for the first time in the world, 5 out of 14 identified mutations are known (c.2806A&gt;T, c.2991-1G&gt;C, c.3158C&gt;G, c.4537C&gt;T, c.6792C&gt;A). The distribution of mutation types turned out to be random. We identified a protective role of crossbreeding for the development of severe manifestations of NF1. We determined a high incidence of scoliosis, short stature, facial dysmorphism and chest deformity in the inheritance of NF1 from the mother, which suggests the influence of modifier genes on the pathogenesis of NF1.

Neurofibromatosis Type 2: A Pandora’s Box of Variable Presentations

Abstract Introduction Neurofibromatosis type 2 (NF2) also known as MISME syndrome stands for multiple inherited schwannomas, meningiomas, and ependymomas in the peripheral and central nervous system. It is a rare disorder of autosomal dominant inheritance due to mutations of a tumor-suppressor gene on the chromosome 22q12. Clinically, it is characterized by multiple benign tumors arising in both the central and peripheral nervous system, particularly from the bilateral vestibular nerve, in more than 90% of the patients, with more than two thirds of them developing spinal tumors. Materials and Methods Here, we studied the variable presentations of cases of NF2, and thorough evaluation of patients was done by contrast MRI of brain and spine. Also, evaluation of ocular manifestations and cutaneous features was done in cases of NF2, and a follow-up was done for a period of 18 months with monitoring of cranial and spinal lesions. Conclusion We studied the various presentations of NF2 and found that a significant proportion of the patients presented with nonvestibular tumors as the initial presentation, with bilateral cerebellopontine angle lesions being an incidental finding; also, the age of presentation in half of the patients was less than 30 years, and so we can conclude that in young patients with spinal tumors or multiple meningiomas, a thorough evaluation regarding family history and various features of NF2 should be done, so that early identification of the disease could be done and patients can be benefitted from timely interventions.

NF1 Tumor Suppressor Gene Inactivation in Juvenile Myelomonocytic Leukemia: New Genetic Evidence and Consequences for Diagnostic Work-up

Neurofibromatosis type 1 (NF-1) predisposes to juvenile myelomonocytic leukemia (JMML) via loss of function of the NF1 tumor suppressor gene and consecutive deregulation of Ras signal transduction. Affected individuals usually carry one defective NF1 allele in the germline; somatic inactivation of the second NF1 allele in hematopoietic cells is associated with transformation to leukemia. We previously demonstrated that a major mechanism for biallelic loss of NF1 function in patients with JMML/NF-1 is mitotic recombination leading to uniparental disomy (UPD) of the 17q chromosome arm (Flotho, 2007; Steinemann, 2010). Using contemporary resequencing and microarray technology, we have now revisited the genetics of NF1 inactivation in JMML. Specifically, we addressed two questions: 1) Are genetic findings in leukemic cells of JMML/NF-1 patients consistent with the clinical diagnosis and the two-hit concept? 2) Does the quintuple-negative (QN) group of JMML (patients without clinical evidence of NF-1 and negative for mutations in PTPN11, KRAS, NRAS, or CBL) contain unrecognized cases likely driven by NF1? We investigated 156 children with JMML registered in studies EWOG-MDS 98 or 2006 and tested for mutations in PTPN11, KRAS, NRAS, and CBL. Twenty-five children (16%) were clinically diagnosed as NF-1 based on &amp;gt;=6 café-au-lait spots (CALS) or family history plus CALS. Family history was positive in 9 JMML/NF-1 patients; &amp;gt;=6, 4, and 1 CALS were described in 23, 1, and 1 patients, respectively. The median age at diagnosis of JMML in the NF-1 group was 35.9 months (range, 4.2 to 71.4). Sixteen children (10%) were grouped as JMML-QN. Granulocyte DNA from bone marrow or peripheral blood collected at time of diagnosis was used for next-generation sequencing of the entire NF1 coding sequence (custom Ampliseq enrichment and Miseq, Illumina). Pathogenicity of NF1 variants was assessed according to ACMG criteria. Affymetrix Cytoscan HD array analysis was applied to detect segmental deletions or copy number-neutral loss of heterozygosity (LOH). Among 25 JMML/NF-1 cases, 8 exhibited an NF1 loss-of-function mutation at near-100% variant allelic frequency (VAF) in combination with UPD involving almost the entire 17q arm, suggesting single mitotic recombination as the leukemic driver. One case had an NF1 mutation at near-100% VAF and segmental 17q UPD, suggesting the unusual occurrence of double mitotic recombination. Nine cases carried two independent pathogenic NF1 mutations at near-50% VAF each; here, germline and somatic events could not be distinguished due to unavailability of non-hematopoietic or parental DNA. Four cases exhibited an NF1 microdeletion in combination with a pathogenic NF1 mutation at near-100% VAF; non-hematopoietic tissue available in 2 of these 4 cases failed to display the mutation, indicating the microdeletion as the constitutional event. A deleterious mutation at 71% VAF but no LOH was revealed in one sample. Only monoallelic evidence of NF1 deficiency was found in 2 cases. In the JMML-QN group, 9/16 cases had previously unrecognized NF1 alterations. Compound-heterozygous pathogenic NF1 mutations were found in 2 and homozygous pathogenic NF1 mutations combined with focal LOH in 3 patients, strongly suggesting NF1 as the JMML driver. In the absence of clinical NF-1 features, the findings in these 5 children may be explained by postzygotic NF1 mosaicism, onset of JMML before clinical manifestation of NF-1, or double somatic NF1 hits in the hematopoietic lineage. Four cases carried monoallelic pathogenic or likely pathogenic NF1 mutations with VAF at ~50% or less, providing inconclusive evidence of driver function as it is also possible that these are secondary hits in a myeloproliferative neoplasm (MPN) driven by an unidentified event. There was no genetic evidence of NF1 involvement in the remaining 7 JMML-QN cases. Several important conclusions can be drawn from our study: The clinical diagnosis is reliable in children with JMML/NF-1; we propose that it can be made on the basis of CALS and JMML alone as the patients are generally too young to display the conventional spectrum of NF-1 features. Children without features of NF-1 should only be assigned to JMML-QN after genetic work-up of NF1 because this will unmask involvement of NF1 in a significant number of cases. In suspected JMML-QN without identifiable NF1 lesion, other forms of MPN should be considered. Disclosures Locatelli: Jazz Pharmaceeutical: Speakers Bureau; Medac: Speakers Bureau; Miltenyi: Speakers Bureau; Bellicum Pharmaceutical: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Amgen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Niemeyer:Celgene: Consultancy; Novartis: Consultancy.