Neurofibromatosis Type 1 Individuals Research Articles

Fungiform Papillae and Gustatory Function in Neurofibromatosis Type 1: A Case-Control Study.

Fungiform papillae enlargement is a common oral manifestation of neurofibromatosis type 1 (NF1). This study aimed to objectively evaluate the size, number, and symmetry of fungiform papillae in NF1 individuals and investigate the relationship between these alterations and taste perception, salivary flow, dietary habits, and BMI. A cross-sectional case-control study was conducted on 80 participants (40 with NF1 and 40 controls), matched by age and sex. Participants underwent quantitative and morphological evaluation of fungiform papillae, gustatory perception tests, sialometry, saliva analysis, xerostomia assessment, dietary assessments, and Body Mass Index calculations. The NF1 group exhibited significantly larger and more asymmetric fungiform papillae and exhibited a higher detection threshold for sweet and sour tastes, as well as hyposalivation and lower preference for healthy foods compared to the controls. No correlation was found between papillae morphology, gustatory perception tests, saliva properties, xerostomia, food preferences, or BMI in the NF1 group. Enlarged and asymmetric fungiform papillae, hyposalivation, heightened sensitivity to sweet and sour tastes, and reduced healthy eating habits were common in NF1. Although fungiform papillae alterations seem unrelated to taste sensitivity and food preferences, further investigation is needed to better understand the mechanisms underlying these changes.

Type 1 Neurofibromatosis Sans Neurofibroma: A Case Report Emphasizing the Role of Ocular Examination

Neurofibromatosis type 1 (NF1) is one of the most common genetic disorders and is inherited in an autosomal dominant fashion. NF1 is a member of the RASopathies, a class of congenital disorders brought on by mutations in the Ras/mitogen-activated protein kinase pathway. Dermatologic manifestations are typically prevalent in NF1 individuals. Multiple café-au-lait macules (CALMs) may be present at birth or develop in the 1st year of life. Other cutaneous manifestations like freckles in the skinfolds appear in early childhood. Neurofibromas are present in almost all adult patients and may be cutaneous, subcutaneous, or along the peripheral nerves, but their appearance may be delayed till adulthood. CALMs and skinfold freckling are not specific for NF1, and we may need to consider other differential diagnoses like Legius syndrome. A recent modification of the diagnostic criteria includes the identification of the genetic abnormality to facilitate diagnosis in children who may not have cutaneous neurofibromas. This emphasizes the added value of genetic analysis in a condition which is generally a clinical diagnosis. Lisch nodules generally occur by about 7 years of age and are present in 90% of cases. Their presence can help differentiate from Legius syndrome with its more benign course without genetic analysis. We report the case of a 14-year-old male with NF1 who had no cutaneous neurofibromas to reiterate the importance of ophthalmic evaluation in all cases of NF1, especially in resource-poor settings where genetic studies may not be possible.

Analysis of the current Covid-19 infection and vaccination status in patients with neurofibromatosis type 1

BackgroundTo investigate the common symptoms after Covid-19 infection, characteristics of adverse events after vaccination, changes in clinical manifestations related to Neurofibromatosis type 1 (NF1), as well as the current vaccination status and factors related to vaccine hesitation among NF1 patients, in order to provide a basis for scientific protection and vaccine acceptance in NF1 individuals in the new phase of pandemic management. MethodsFrom December 29, 2022, to January 10, 2023, we conducted a self-assessment questionnaire survey among diagnosed NF1 patients. General data were provided including sex, age, main clinical presentations, and current treatment. This study mainly focused on the infection and vaccination status of Covid-19 among these patients with NF1. The data were statistically analyzed using SPSS26.0 software. ResultsOf the 250 questionnaires distributed, 226 were valid. Among the 164 patients (72.6%) with Covid-19 infection, the most common infection symptoms and incidence of patients were not significantly different from those in the normal population (P>0.05), but the incidence of symptoms such as nasal congestion, headache, myalgia, sore throat, abdominal pain, diarrhea, and eye discomfort was higher than that in the normal population (P<0.05), and no severe infection was observed; 186 patients (82.3%) had completed the Covid-19 vaccination, and more than half of those who were not vaccinated had no plans for vaccination. Among the vaccinated patients, there was no significant difference in the incidence of adverse events, such as fever, pain, redness, and swelling at the injection site after vaccination, compared to the normal population (P>0.05), but the incidence of fatigue and headache was higher in NF1 patients (P<0.001). Most patients with NF1 believe that there is no significant progressive change in NF1-related clinical manifestations after Covid-19 infection and vaccination. ConclusionCurrently, some NF1 patients appear to be worried about the evolution of their disease after Covid-19 infection in the face of large fluctuations in the pandemic situation, and some patients hesitate to receive the vaccine due to their special disease condition. Thus, clinical trials should be conducted to develop a refined pandemic response and vaccination program for this special group.

Sexual Self-Esteem and Psychological Burden of Adults With Neurofibromatosis Type 1.

Neurofibromatosis type 1 (NF1) is one of the most common tumor predisposition syndromes which primarily affects the skin. NF1 is characterized by various degrees of skin tumors and pigmentation abnormalities such as café-au-lait macules. Other skin diseases, such as psoriasis or neurodermatitis, have a negative influence on sexuality and quality of life and represent a psychological burden for those affected. The present study investigated the extent to which skin tumors (disfigurement) are related to sexuality and psychosocial factors in NF1 individuals. An anonymous online survey was carried out on Facebook and the webpage of the German Neurofibromatosis Association and a total of 166 persons participated. Of these participants, 92 were affected by NF1.74 healthy persons took part in the survey as a comparative group. Results show a significant relation between sexuality, body image, quality of life and the presence of depressive symptoms of the NF1 affected persons. Individuals with NF1 show a more negative sexual self-esteem. These concerns should be taken into account in NF1- related health care approaches.

NIMG-08. A MULTI-CENTER RADIOMICS-BASED MODEL TO DIFFERENTIATE BETWEEN NEUROFIBROMATOSIS TYPE 1-ASSOCIATED PLEXIFORM NEUROFIBROMAS AND MALIGNANT PERIPHERAL NERVE SHEATH TUMORS

Abstract BACKGROUND Several MRI features are proposed to distinguish between plexiform neurofibromas (PNF) and malignant peripheral nerve sheath tumors (MPNST) in neurofibromatosis type 1 (NF1), including tumor size, margins, and degree of heterogeneity. However, most of these features are descriptive in nature, subject to intra-/interrater variability, and based on small single-institution studies. The goal of this study was to identify radiomic features that can differentiate between NF1-associated PNF and MPNST. METHODS 31 MPNSTs and 24 PNFs from five centers were segmented on short TI inversion recovery sequences using a semi-automated segmentation software (3DQI). Standard pre-processing was performed, including N4 bias field correction, intensity normalization (using a mean of 120 SI and standard deviation of 80 SI), and resampling to 1 mm3 voxel resolution. 1688 radiomic features were extracted from the tumor region of interest using PyRadiomics, an open-source Python radiomics package. To classify tumors as PNF or MPNST, we implemented the Boruta algorithm and correlation removal for selection of important features. A Random Forest model was built using the top ten selected features. Five-fold cross-validation was performed and repeated 100 times. Model performance was evaluated using the area under the ROC curve (AUC), sensitivity, specificity, accuracy, and confidence intervals. RESULTS The top ten features included in the model were five intensity features, two shape features, and three texture features. The model demonstrated an AUC of 0.891 (95% CI 0.882-0.899), sensitivity of 0.744, specificity of 0.847, and accuracy of 0.802 (95% CI 0.792-0.813). CONCLUSIONS Our machine learning model demonstrated high performance in classifying tumors as either PNF or MPNST in NF1 individuals. Inclusion of additional tumors for model training and testing on an independent dataset are underway. Ultimately, our model may enable improved differentiation between PNF and MPNST compared to descriptive MRI features, permit early patient risk stratification, and improve patient outcomes.

Using antisense oligonucleotides for the physiological modulation of the alternative splicing of NF1 exon 23a during PC12 neuronal differentiation

Neurofibromatosis Type 1 (NF1) is a genetic condition affecting approximately 1:3500 persons worldwide. The NF1 gene codes for neurofibromin protein, a GTPase activating protein (GAP) and a negative regulator of RAS. The NF1 gene undergoes alternative splicing of exon 23a (E23a) that codes for 21 amino acids placed at the center of the GAP related domain (GRD). E23a-containing type II neurofibromin exhibits a weaker Ras-GAP activity compared to E23a-less type I isoform. Exon E23a has been related with the cognitive impairment present in NF1 individuals. We designed antisense Phosphorodiamidate Morpholino Oligomers (PMOs) to modulate E23a alternative splicing at physiological conditions of gene expression and tested their impact during PC12 cell line neuronal differentiation. Results show that any dynamic modification of the natural ratio between type I and type II isoforms disturbed neuronal differentiation, altering the proper formation of neurites and deregulating both the MAPK/ERK and cAMP/PKA signaling pathways. Our results suggest an opposite regulation of these pathways by neurofibromin and the possible existence of a feedback loop sensing neurofibromin-related signaling. The present work illustrates the utility of PMOs to study alternative splicing that could be applied to other alternatively spliced genes in vitro and in vivo.

Genetic basis of neurofibromatosis type 1 and related conditions, including mosaicism.

Neurofibromatosis type 1 (NF1) is a frequent autosomal dominant disorder characterised by café-au-lait maculae (CALM), skinfold freckling, iris Lisch nodules and benign peripheral nerve sheath tumours (neurofibromas). The NF1 gene is a tumour suppressor gene and NF1 individuals have an increased risk for a long list of tumours, all resulting from a second hit in the normal copy of the NF1 gene. Remarkably, some non-tumour phenotypes such as CALM and pseudarthrosis are also caused by a "second hit". Germline mutations inactivating the NF1 gene show a large variability in genetic mechanisms ranging from single-nucleotide substitutions and somatic mosaicism to large deletions affecting neighbouring genes. Molecular confirmation of the clinical diagnosis is becoming increasingly more important to differentiate NF1 from other syndromes such as Legius syndrome, to investigate genotype-phenotype correlations relevant in 10% of cases and to detect somatic mosaicism. Some degree of learning difficulties, attention deficit and social problems are observed in most children and affect quality of life. There is a large individual variability in complications and the evolution of the disease is difficult to predict. Specialised outpatient clinics for children have been widely established and are important for surveillance and guidance. Regular surveillance is also important for adolescents and adults because many tumour complications can be detected by whole-body MRI and treated even before symptoms develop and irreversible damage occurs. Recent data on nodular plexiform neurofibromas with continued growth in adolescents and young adults show that many of these tumours are premalignant lesions called atypical neurofibromatous neoplasm of uncertain biological potential (ANNUBP). Specific surveillance and timely local resection of these benign peripheral nerve sheath tumours might be important to prevent malignant degeneration. In the last years, targeted therapy with MEK inhibitors has shown promise to treat unresectable and symptomatic plexiform neurofibromas. Many more challenges remain to find the best way to monitor children and adults for potential complications and to find a satisfying cure for many complications in this disorder.

Quality of life in patients with neurofibromatosis type 1 and 2 in Canada.

BackgroundThere is scarce data on the quality of life of people with neurofibromatosis type 1 (NF1) and type 2 (NF2) in Canada.MethodsA cross-sectional study of adults with NF1 and NF2 attending a tertiary center. Patients completed generic measures (SF-36, EQ-5D-5L, and PROMIS pain interference) and disease-specific questionnaires (PedsQL NF1 module and the NFTI-QOL for NF2). We compared generic scores between NF1 and NF2 individuals and used regression models to assess factors associated with quality of life.ResultsHundred and eighty-four participants were enrolled. Mean age was 33 years in NF1 and 40 years in NF2. NF1 and NF2 individuals had lower employment rates and lower scores in all domains of the SF-36 compared to the general Canadian population (P < .005). Using the EQ-5D-5L, there was a high proportion of pain (64% in NF1 and 74% in NF2) and anxiety/depression (60% in NF1 and 68% in NF2). Pain interference correlated with poor quality of life in NF1 and NF2; perceived physical appearance was the main predictor of mental well-being in NF1.ConclusionsIndividuals with NF1 and NF2 have low quality of life, and this correlates with pain, anxiety, and depression, which are prevalent in NF1 and NF2. Perceived physical appearance predicts quality of life in NF1. A multidisciplinary approach is necessary for patients with NF1 and NF2, including mental health and pain management.

Reprogramming Captures the Genetic and Tumorigenic Properties of Neurofibromatosis Type 1 Plexiform Neurofibromas.

SummaryNeurofibromatosis type 1 (NF1) is a tumor predisposition genetic disease caused by mutations in the NF1 tumor suppressor gene. Plexiform neurofibromas (PNFs) are benign Schwann cell (SC) tumors of the peripheral nerve sheath that develop through NF1 inactivation and can progress toward a malignant soft tissue sarcoma. There is a lack of non-perishable model systems to investigate PNF development. We reprogrammed PNF-derived NF1(−/−) cells, descendants from the tumor originating cell. These NF1(−/−)-induced pluripotent stem cells (iPSCs) captured the genomic status of PNFs and were able to differentiate toward neural crest stem cells and further to SCs. iPSC-derived NF1(−/−) SCs exhibited a continuous high proliferation rate, poor myelination ability, and a tendency to form 3D spheres that expressed the same markers as their PNF-derived primary SC counterparts. They represent a valuable model to study and treat PNFs. PNF-derived iPSC lines were banked for making them available.

Autonomic thermoregulatory dysfunction in neurofibromatosis type 1.

Neurofibromatosis type 1 (NF1) causes neural and cutaneous disorders and reduced exercise capacity. Exercise/heat exposure increasing internal temperature must be compensated by eccrine sweat function and warmed skin vasodilation. We suspected NF1 could adversely affect eccrine sweat function and/or vascular thermoregulatory responses (VTR). The eccrine sweat function and VTR of 25 NF1 volunteers (14 males, 11 females; 16-57 years old) were compared with 23 non-NF1 controls matched by sex, age, height and weight (CG). Sweating was induced by 1) pilocarpine 1% iontophoresis (PILO); and 2) by passive heating (HEAT) via the lower third of the legs being immersed in 42°C water for one hour. Previously established eccrine sweat function and VTR protocols were used. The NF1 group showed: a) lower sweat rate than the CG group during PILO; b) a smaller diastolic pressure decrease; and c) higher tympanic temperatures than controls during HEAT (p < 0.05). Reduced sweating and vascular thermoregulatory responses suggest autonomic dysfunction in NF1 individuals.

Analysis of Neurofibromatosis Type 1 (NF1) Children and Adolescents? Weight, Length and Head Circumference - A Cross-Sectional Study

Objective: The main purpose of this study was to carry out a clinical evaluation about anthropometric measurements (weight, length and head circumference) of a group of Brazilian Neurofibromatosis type 1 (NF1) children and adolescent individuals. Patients and Methods: This was an observational and cross-sectional study. The patient sample included 146 children and adolescents of both sexes; aged zero to 19 years and each individual was measured just once. The dispersion of the anthropometric measurements was evaluated and their position in relation to the percentiles of standard WHO growth charts were used as a reference in pediatric practice. Results: Short stature was present in 17.1% of the subjects; the higher frequency was observed in males aged 5-19 years (20.4%). The heritability of NF1 in patients with short stature was not statistically significant (p value >0.05) when we compared the individuals that presented short stature or not and positive or negative familial history of NF1 using a 2×2 Table (χ2 analysis). In males, the percentage of low birth weight was 5.5% while in females it was 1.4%. The percentage of underweight individuals was 3.7%. Macrocephaly was observed in 25.0% of boys and girls aged 0-5 years. Conclusions: In a group of Brazilian NF1 patients, we found cases of short stature even in the first five years of life. Weight below percentile 50 was predominant in girls aged 0-5 years (72.2%) and head circumference above percentile 50 with macrocephaly was also present. Birth’s mean weight and length below average apparently are not general characteristics of NF1 individuals from Brazil.

Neurofibromin deficiency-associated transcriptional dysregulation suggests a novel therapy for tibial pseudoarthrosis in NF1.

Neurofibromatosis type 1 (NF1) is an autosomal dominant disease caused by mutations in NF1. Among the earliest manifestations is tibial pseudoarthrosis and persistent nonunion after fracture. To further understand the pathogenesis of pseudoarthrosis and the underlying bone remodeling defect, pseudoarthrosis tissue and cells cultured from surgically resected pseudoarthrosis tissue from NF1 individuals were analyzed using whole-exome and whole-transcriptome sequencing as well as genomewide microarray analysis. Genomewide analysis identified multiple genetic mechanisms resulting in somatic biallelic NF1 inactivation; no other genes with recurring somatic mutations were identified. Gene expression profiling identified dysregulated pathways associated with neurofibromin deficiency, including phosphoinositide 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) signaling pathways. Unlike aggressive NF1-associated malignancies, tibial pseudoarthrosis tissue does not harbor a high frequency of somatic mutations in oncogenes or other tumor-suppressor genes, such as p53. However, gene expression profiling indicates that pseudoarthrosis tissue has a tumor-promoting transcriptional pattern, despite lacking tumorigenic somatic mutations. Significant overexpression of specific cancer-associated genes in pseudoarthrosis highlights a potential for receptor tyrosine kinase inhibitors to target neurofibromin-deficient pseudoarthrosis and promote proper bone remodeling and fracture healing.

Auditory temporal processing deficits and language disorders in patients with neurofibromatosis type 1

Previous findings from a case report led to the argument of whether other patients with neurofibromatosis type 1 (NF1) may have abnormal central auditory function, particularly auditory temporal processing. We hypothesized that it is associated with language and learning disabilities in this population. The aim of this study was to measure central auditory temporal function in NF1 patients and correlate it with the results of language evaluation tests. A descriptive/comparative study including 25 NF1 individuals and 22 healthy controls compared their performances on audiometric evaluation and auditory behavioral testing (Sequential Verbal Memory, Sequential Non-Verbal Memory, Frequency Pattern, Duration Pattern, and Gaps in Noise Tests). To assess language performance, two tests (phonological and syntactic awareness) were also conducted. The study showed that all participants had normal peripheral acoustic hearing. Differences were found between the NF1 and control groups in the temporal auditory processing tests [Sequential Verbal Memory (P=0.009), Sequential Non-Verbal Memory (P=0.028), Frequency Patterns (P=0.001), Duration Patterns (P=0.000), and Gaps in Noise (P=0.000)] and in language tests. The results of Pearson correlation analysis demonstrated the presence of positive correlations between the phonological awareness test and Frequency Patterns humming (r=0.560, P=0.001), Frequency Patterns labeling (r=0.415, P=0.022) and Duration Pattern humming (r=0.569, P=0.001). These results suggest that the neurofibromin deficiency found in NF1 patients is associated with auditory temporal processing deficits, which may contribute to the cognitive impairment, learning disabilities, and attention deficits that are common in this disorder.Learning outcomes: The reader will be able to: (1) describe the auditory temporal processing in patients with neurofibromatosis type 1; and (2) describe the impact of the auditory temporal deficits in language in this population.

Fractures in Children With Neurofibromatosis Type 1 From Two NF Clinics

Neurofibromatosis type 1 (NF1) is an autosomal dominant genetic disorder with osseous abnormalities occurring in up to one-third of patients. Several studies have documented osteopenia in both children and adults with NF1; however, the significance of lower bone mineral density (BMD) in relationship to fracture incidence is not well elucidated in NF1, particularly in children. We undertook a retrospective study to determine prevalence and location of fractures in children and adolescents with NF1, ages 5-20 years, using a standardized questionnaire. We surveyed 256 individuals with NF1 from two multidisciplinary NF centers and 178 controls without NF1 of similar ages and sex. Participants with known long bone dysplasia (LBD) were analyzed separately. Data collected included numbers and location of fractures, dietary calcium intake, and physical activity levels. There was no difference in prevalence of ever having a fracture between the NF1 group without LBD (22%) and the control group (25%); median number of fractures also did not differ. There were significant differences in fracture location with a higher frequency of fractures of the lower extremities in NF1 individuals without LBD compared to controls. Both NF1 cohorts had lower rates of physical activity than controls (P < 0.0001). Our data demonstrate that the likelihood of having had a fracture is not higher in young NF1 individuals without LBD in comparison to healthy controls. The lower physical activity level may have a "protective effect" for those with NF1, thus keeping their fracture incidence lower than expected for their relative degree of osteopenia.

Multivariate pattern analysis reveals subtle brain anomalies relevant to the cognitive phenotype in neurofibromatosis type 1

Neurofibromatosis Type 1 (NF1) is a common genetic condition associated with cognitive dysfunction. However, the pathophysiology of the NF1 cognitive deficits is not well understood. Abnormal brain structure, including increased total brain volume, white matter (WM) and grey matter (GM) abnormalities have been reported in the NF1 brain. These previous studies employed univariate model-driven methods preventing detection of subtle and spatially distributed differences in brain anatomy. Multivariate pattern analysis allows the combination of information from multiple spatial locations yielding a discriminative power beyond that of single voxels. Here we investigated for the first time subtle anomalies in the NF1 brain, using a multivariate data-driven classification approach. We used support vector machines (SVM) to classify whole-brain GM and WM segments of structural T1 -weighted MRI scans from 39 participants with NF1 and 60 non-affected individuals, divided in children/adolescents and adults groups. We also employed voxel-based morphometry (VBM) as a univariate gold standard to study brain structural differences. SVM classifiers correctly classified 94% of cases (sensitivity 92%; specificity 96%) revealing the existence of brain structural anomalies that discriminate NF1 individuals from controls. Accordingly, VBM analysis revealed structural differences in agreement with the SVM weight maps representing the most relevant brain regions for group discrimination. These included the hippocampus, basal ganglia, thalamus, and visual cortex. This multivariate data-driven analysis thus identified subtle anomalies in brain structure in the absence of visible pathology. Our results provide further insight into the neuroanatomical correlates of known features of the cognitive phenotype of NF1.

Unidentified bright objects in neurofibromatosis type 1: Conventional MRI in the follow-up and correlation of microstructural lesions on diffusion tensor images

Purpose To evaluate the evolution of unidentified bright objects (UBOs) in individuals with neurofibromatosis type 1 (NF1) by serial magnetic resonance imaging (MRI), and to relate this to regional fractional anisotropy (FA). Materials and Methods The signal pattern of the T2-weighted sequences in the basal ganglia, thalamus, brain stem, and cerebellum for 27 NF1 individuals and a control group were analyzed by diffusion tensor imaging (DTI). The presence or absence of UBOs in 2 consecutive MRI examinations was related to FA. Results We demonstrated significant differences in FA for the basal ganglia, cerebellum, and thalamus between NF1 patients and controls ( P ≤ 0.05), even with a reduction or disappearance of UBOs. Conclusions MRI allows for adequate monitoring of the temporal and spatial distribution of UBOs in patients with NF1. DTI confirmed changes in FA despite the disappearance or reduction of UBOs, thereby confirming the hypothesis that microstructural damage occurs in specific brain regions of NF1 patients.

NF1 exon 22 analysis of individuals with the clinical diagnosis of neurofibromatosis type 1

Café-au-lait macules are frequently seen in Ras-MAPK pathway disorders and are a cardinal feature of neurofibromatosis type 1 (NF1). Most NF1 individuals develop age-related tumorigenic manifestations (e.g., neurofibromas), although individuals with a specific 3-bp deletion in exon 22 of NF1 (c.2970_2972delAAT) have an attenuated phenotype with primarily pigmentary manifestations. Previous reports identify this deletion c.2970_2972delAAT in exon 17 of NF1 using NF Consortium nomenclature. For this report, we elected to use standard NCBI nomenclature, which places this identical deletion within exon 22. SPRED1 mutations cause Legius syndrome, which clinically overlaps with this attenuated NF1 phenotype. In an unselected cohort of 50 individuals who fulfilled NIH clinical diagnostic criteria from an NF Clinic and did not have SPRED1 mutations, we sequenced NF1 exon 22 in order to identify children and adolescents with multiple café-au-lait spots who could be projected to have lower likelihood to develop tumors. Two individuals with NF1 exon 22 mutations were identified: an 11-year-old boy with the c.2970_2972delAAT in-frame deletion and a 4-year-old boy with c.2866dupA. The father of the second patient had an attenuated form of NF1 and showed 24% germline mosaicism of the c.2866dupA mutation in whole blood. These individuals emphasize the need for mutation analysis in some individuals with the clinical diagnosis of NF1 who lack the tumorigenic or classic skeletal abnormalities of NF1. Specifically, with the identification of Legius syndrome, the need to recognize the attenuated phenotype of NF1 mosaicism and confirmation by mutation analysis is increasingly important for appropriate medical management and family counseling.

Tibial geometry in individuals with neurofibromatosis type 1 without anterolateral bowing of the lower leg using peripheral quantitative computed tomography

IntroductionLower leg bowing with tibial pseudarthrosis is associated with neurofibromatosis type 1 (NF1). The objective of the study is to determine if the geometry of the lower limb in individuals with neurofibromatosis type 1 (NF1) differs from controls, and to characterize the osseous components of the tibia in NF1. MethodsPeripheral quantitative computed tomography (pQCT) of the lower limb was performed (90 individuals with NF1 without tibial and/or fibular dysplasia: 474 healthy individuals without NF1). Subjects were 4–18 years of age. Individuals with NF1 were compared to controls using an analysis-of-covariance with a fixed set of covariates (age, weight, height, Tanner stage, and gender). ResultsUsing pQCT, NF1 individuals without bowing of the lower leg have smaller periosteal circumferences (p<0.0001), smaller cortical area (p<0.0001), and decreased tibial cortical and trabecular bone mineral content (BMC) (p<0.0001) compared to controls. DiscussionIndividuals with NF1 have a different geometry of the lower leg compared to healthy controls suggesting that NF1 haploinsufficiency impacts bone homeostasis although not resulting in overt anterolateral bowing of the lower leg.

Evidence of Increased Bone Resorption in Neurofibromatosis Type 1 Using Urinary Pyridinium Crosslink Analysis

Although neurofibromatosis type 1 (NF1) is a neurocutaneous disorder, skeletal abnormalities such as long-bone dysplasia, scoliosis, sphenoid wing dysplasia, and osteopenia are observed. To investigate the role of bone resorption as a mechanism for the bony abnormalities, we selected urinary pyridinium crosslinks (collagen degradation products excreted in urine) as a measure of bone resorption in NF1. Bone resorption was evaluated by quantitative assessment of the urinary excretion of pyridinium crosslinks [pyridinoline (Pyd) and deoxypyridinoline (Dpd)]. Total (free plus peptide-bound) pyridinium crosslinks from the first morning urines from 59 NF1 children (ages 5-19) were extracted and analyzed (17 children with a localized skeletal dysplasia, and 42 without). The data were compared with a healthy reference population without NF1 (n = 99). Multivariate analyses, controlling for age showed statistically significant increases for Dpd (p < 0.001) and the Dpd/Pyd ratio (p < 0.001) in NF1 individuals with and without a skeletal dysplasia. NF1 children have an increase in the urinary excretion of pyridinium crosslinks, reflecting increased bone resorption. The effects of NF1 haploinsufficiency likely contribute to abnormal bone remodeling, either directly or indirectly by aberrant Ras signaling, potentially predisposing NF1 individuals to localized skeletal defects.

GermlineNF1Mutational Spectra and Loss-of-Heterozygosity Analyses in Patients with Pheochromocytoma and Neurofibromatosis Type 1

Neurofibromatosis type 1 (NF1) is a pheochromocytoma-associated syndrome. Because of the low prevalence of pheochromocytoma in NF1, we ascertained subjects by pheochromocytoma that also had NF1 in the hope of describing the germline NF1 mutational spectra of NF1-related pheochromocytoma. An international registry for NF1-pheochromocytomas was established. Mutation scanning was performed using denaturing HPLC for intragenic variation and quantitative PCR for large deletions. Loss-of-heterozygosity analysis using markers in and around NF1 was performed. There were 37 eligible subjects (ages 14-70 yr). Of 21 patients with corresponding tumor available, 67% showed somatic loss of the nonmutated allele at the NF1 locus vs. 0 of 12 sporadic tumors (P = 0.0002). Overall, 86% of the 37 patients had exonic or splice site mutations, 14% large deletions or duplications; 79% of the mutations are novel. The cysteine-serine rich domain (CSR) was affected in 35% but the RAS GTPase activating protein domain (RGD) in only 13%. There did not appear to be an association between any clinical features, particularly pheochromocytoma presentation and severity, and NF1 mutation genotype. The germline NF1 mutational spectra comprise intragenic mutations and deletions in individuals with pheochromocytoma and NF1. NF1 mutations tended to cluster in the CSR over the RAS-GAP domain, suggesting that CSR plays a more prominent role in individuals with NF1-pheochromocytoma than in NF1 individuals without this tumor. Loss-of-heterozygosity of NF1 markers in NF1-related pheochromocytoma was significantly more frequent than in sporadic pheochromocytoma, providing further molecular evidence that pheochromocytoma is a true component of NF1.