Mosaic Neurofibromatosis Type Research Articles

HGG-40. NF1 mosaicism in a CMMRD-patient with a glioblastoma

Constitutional Mismatch Repair Deficiency (CMMRD) and Neurofibromatosis type 1 (NF1) are brain tumor predisposing syndromes associated with café-au-lait macules (CALM). Due to this overlap, establishing the differential diagnosis can be difficult, but remains crucial as treatments and surveillance protocols clearly differ for affected patient according to the underlying disease. We reported a girl, with a clinical diagnosis of sporadic NF1 during childhood, who presented a glioblastoma at 16 years-old. Faced with the NF1-like phenotype, diagnosis of CMMRD was suspected because tumor was ultra-hypermutated (228.67 mut/Mb), with a loss of PMS2 expression in both tumor and normal cells. Germline analyses identified a compound heterozygous pathogenic variant (PV) in the PMS2 gene, with an abnormal methylation tolerance test, that confirmed CMMRD. Moreover, a NF1 PV (20% and 9% in blood and saliva samples respectively) was identified compatible with a germline mosaicism. Patient's phenotype was atypical for CMMRD, with a voluminous neurofibroma and ephelids rather observed in NF1. CMMRD oncogenesis is not currently understood, in particular involvement of an NF1 PV, which could arise early from the ultra-hypermutated burden and might explain clinical signs, in particular CALMs. CMMRD diagnosis allowed proposing an adapted genetic counseling and surveillance for the patient and her parents according to the published guidelines due to the major impact on the patient’s oncological risks and prognosis. The best strategy for surveillance of the neurofibroma is still debated due to uncertainties about its risk of degeneration with a CMMRD underlying disease. This observation raises the question of the frequency of mosaic NF1 germline PV in CMMRD-patients and the time of its postzygotic appearance in the context of a biallelic deficit of one of the MMR genes. Combination of these both CMMRD and NF1 germline PVs would be a strong argument for a combination of MEK-inhibitors with immunotherapy.

Value of a café-au-lait macules screening clinic: Experience from The Hospital for Sick Children in Toronto.

Café-au-lait macules (CALMs) are a characteristic feature of neurofibromatosis type 1 (NF1), but also occur in other genetic disorders. Differential diagnosis of CALMs remains challenging and can be stressful for families. We sought to examine the role of an established CALMs screening clinic in diagnosing CALMs-related disorders. We retrospectively reviewed patients seen between July 2012 and January 2019 in a CALMs screening clinic at The Hospital for Sick Children, a tertiary pediatric hospital in Toronto, Canada. Pediatric patients were referred because of multiple CALMs or suspected NF1. Selection was based on a chronological referral sample with no exclusions. A pediatric dermatologist examined all patients for CALMs and NF1manifestations. Genetic testing was offered to confirm a clinical diagnosis or when clinical findings were inconclusive. Three hundred patients, of which 152 (50.7%) were female and had a mean age of 5.6±4.8years were seen during the study period. NF1 was diagnosed in 76 (25.3%) patients, mosaic NF1 in 38 (12.7%) patients, and 8 (2.7%) patients received other genetic diagnoses. One hundred and twelve (37.3%) patients were diagnosed with isolated CALMs not associated with an underlying genetic disease. Furthermore, 36 (12%) of our patients did not have CALMs. The CALMs screening clinic aided in the early diagnosis of genetic disorders such as NF1 and distinguished CALMs from other hyperpigmented lesions. We encourage the adoption of this clinic model in referral centers to streamline and optimize care of patients with presumptive diagnosis of CALMs.

Mosaic neurofibromatosis type 1 or segmental neurofibromatosis: what is in the name?

Mosaic neurofibromatosis type 1 or segmental neurofibromatosis: what is in the name?

Patient-derived iPSC-cerebral organoid modeling of the 17q11.2 microdeletion syndrome establishes CRLF3 as a critical regulator of neurogenesis.

SUMMARYNeurodevelopmental disorders are often caused by chromosomal microdeletions comprising numerous contiguous genes. A subset of neurofibromatosis type 1 (NF1) patients with severe developmental delays and intellectual disability harbors such a microdeletion event on chromosome 17q11.2, involving the NF1 gene and flanking regions (NF1 total gene deletion [NF1-TGD]). Using patient-derived human induced pluripotent stem cell (hiPSC)-forebrain cerebral organoids (hCOs), we identify both neural stem cell (NSC) proliferation and neuronal maturation abnormalities in NF1-TGD hCOs. While increased NSC proliferation results from decreased NF1/RAS regulation, the neuronal differentiation, survival, and maturation defects are caused by reduced cytokine receptor-like factor 3 (CRLF3) expression and impaired RhoA signaling. Furthermore, we demonstrate a higher autistic trait burden in NF1 patients harboring a deleterious germline mutation in the CRLF3 gene (c.1166T>C, p.Leu389Pro). Collectively, these findings identify a causative gene within the NF1-TGD locus responsible for hCO neuronal abnormalities and autism in children with NF1.

Targeted deep sequencing of DNA from multiple tissue types improves the diagnostic rate and reveals a highly diverse phenotype of mosaic neurofibromatosis type 2

BackgroundAlthough 60% of patients with de novo neurofibromatosis type 2 (NF2) are presumed to have mosaic NF2, the actual diagnostic rate of this condition remains low at around 20% because...

Mosaic Neurofibromatosis Type 1 With Multiple Cutaneous Diffuse and Plexiform Neurofibromas of the Lower Leg

Neurofibromatosis type 1 (NF1) is an autosomal dominant hereditary disease with complete penetrance and a very variable phenotype. Recent research has shown that postzygotic NF1 gene mutations occur to a far greater extent than previously thought. The phenotype of affected individuals reflects the time of somatic mutation and the phenotype is correspondingly diverse. This report describes histological and genetic findings in a case of mosaic NF1, the clinical control of which documents almost stationary skin findings over a period of 9 years. The 55-year-old female first presented for advice on a strip of nodular skin tumours of the calf skin. She had no hallmarks of NF1. It was only 9 years later that she had the skin tumours removed, all of which were partially diffuse and partially plexiform neurofibroma. The genetic examination showed an atypical large deletion of the NF1 gene in the skin tumours, but not in overlying skin or blood. Segmental NF1 is a distinct type of mosaic/somatic NF1 mutation. The phenotype of diffuse and plexiform skin neurofibromas can resemble cutaneous neurofibroma. Surgical therapy for segmental neurofibromatosis does not differ from the concepts for treating nerve sheath tumours in NF1 patients with a germline NF1 mutation.

MON-072 A 2 -Year Old Girl with Turner Syndrome and Neurofibromatosis Type 1

Introduction: Turner syndrome (TS) occurs due to loss of either all or part of the X chromosome, in some or all the cells of the body. The most consistent features of TS are short stature and premature ovarian failure. Neurofibromatosis type 1 (NF1) is an inheritable in an autosomal dominant manner tumor predisposition syndrome and is caused by loss-of-function mutations in the tumor suppressor NF1 gene (neurofibromin 1). Literature review indicated rare cases with NF1 and TS (1). We report the sixth girl with mosaic TS and NF1 who presented with optic nerve glioma. Case report: A 2-year-old female presented to us due to short stature. Her height was 2,5 SD lower than the mean parental height curve, and her bone age was delayed only by 3 months. She already had a normal (46XX) peripheral blood karyotype (70 mitoses). She had abnormal body proportions and with short limbs with unremarkable café au lait spots. Additionally, to the short stature laboratory investigation we ordered a gene panel to exclude hypochondroplasia, and a Karyotype in fibroblasts culture from oral cavity sample. The results revealed low IGF-1 and mosaic TS in 14%. We preformed 2 provocative tests which revealed low growth hormone peak < 5 ng/ml. A brain and pituitary MRI to exclude pituitary lesions or structural abnormalities revealed gliomas of the optic chiasma and the right optic nerve with characteristic NF1 “spots” (regions of signal abnormality in T2 sequences) involving the basal ganglia, cerebellum and the right temporal lobe. DNA sequencing targeted to a gene panel related to NF1 and NF2 revealed a novel de novo heterozygous NF1 gene mutation in exon 28 [3764Α>G];[=]p.[Gln1255Arg]. Discussion: NF1- Gliomas are most commonly seen in young children, (mean 4.5 years). Only 1/3 of affected children will require therapeutic intervention. However early diagnosis, of optic gliomas is important. Our patient was completely asymptomatic by the time of diagnosis and no other symptom or sign of NF1 was apparent. Ophthalmologic examination was normal, but visual electrophysiologic testing was abnormal as far the right optic nerve is concerned. The oncology team decided to preform chemotherapy. In TS impaired growth is related to resistance in GH. Some studies suggested that there could be a relationship between GHD and NF1 even in the absence of an organic pituitary damage. In our patient it has been decided not to treat with GH and closely track the patient’s growth. Conclusion: Coexistence of NF1 with TS is rare. Awareness is needed as early identification and treatment of CNS gliomas can prevent visual loss and severe co-morbidities.1.Rare Presentation of Neurofibromatosis and Turner Syndrome in a Pediatric Patient. Pediatr Rep. 2017 Jun 26; 9(2): 6810

NF1-like optic pathway gliomas in children: clinical and molecular characterization of this specific presentation.

BackgroundPediatric neurofibromatosis type 1 (NF1)–associated optic pathway gliomas (OPGs) exhibit different clinico-radiological features, treatment, and outcome compared with sporadic OPGs. While NF1-associated OPGs are caused by complete loss-of-function of the NF1 gene, other genetic alterations of the RAS-MAPK pathway are frequently described in the sporadic cases. We identified a group of patients who presented OPGs with typical radiological features of NF1-associated OPGs but without the NF1 diagnostic criteria. We aim to investigate into the possible molecular mechanisms underlying this “NF1-like” pediatric OPGs presentation.MethodsWe analyzed clinico-radiological features of 16 children with NF1-like OPGs and without NF1 diagnostic criteria. We performed targeted sequencing of the NF1 gene in constitutional samples (n = 16). The RAS-MAPK pathway major genes were sequenced in OPG tumor samples (n = 11); BRAF FISH and IHC analyses were also performed.ResultsIn one patient’s blood and tumor samples, we identified a NF1 nonsense mutation (exon 50: c.7285C>T, p.Arg2429*) with ~8% and ~70% VAFs, respectively, suggesting a mosaic NF1 mutation limited to the brain (segmental NF1). This patient presented signs of neurodevelopmental disorder. We identified a somatic alteration of the RAS-MAPK pathway in eight tumors: four BRAF activating p.Val600Glu mutations, three BRAF:KIAA oncogenic fusions, and one putative gain-of-function complex KRAS indel inframe mutation.ConclusionsNF1-like OPGs can rarely be associated with mosaic NF1 that needs specific constitutional DNA analyses for diagnosis. Further studies are warranted to explore unknown predisposition condition leading to the NF1-like OPG presentation, particularly in patients with the association of a neurodevelopmental disorder.

Malignant peripheral nerve-sheath tumors in an adolescent patient with mosaic localized NF1: A case report.

Malignant peripheral nerve-sheath tumors (MPNSTs) are rare malignancies that are often observed in patients with neurofibromatosis type 1 (NF1). However, the occurrence of MPNST associated with mosaic localized NF1 is extremely rare. Previous reports have revealed that MPNST was associated with mosaic localized NF1 in only three patients who were >40 years of age. The present report details a 16-year-old man who presented with pain and a 3 cm mass on the medial side of the right knee. Magnetic resonance imaging revealed a circumscribed soft tissue tumor located in the subcutaneous tissue. His previous doctor believed that it was benign and conducted a marginal resection. However, postoperative histology results demonstrated spindle cell sarcoma, following which the patient was referred to The Osaka International Cancer Institute. Localized café-au-lait spots were identified in the affected leg, which inferred that the patient had NF1-related MPNST. A wide resection was performed to completely resect the residual tumor; however, a definitive histological diagnosis was challenging due to the small residual tumor. Hence, the genomic mutations of NF1 in the regional café-au-lait spots were analyzed. The result revealed an NF1 microdeletion and a consistently limited expression of NF1 in the tumor sample. Finally, the patient was diagnosed with MPNST with mosaic localized NF1. Local recurrence and distant metastasis were not observed 1.5 years after surgery. In conclusion, the present report presented MPNST in an adolescent patient with mosaic localized NF1. The occurrence of MPNSTs correlated with mosaic localized NF1 is extremely rare. However, it is of high-grade malignancy and therefore, its clinical features should be considered by orthopedists and pathologists.

85P - Improving detection level of somatic mosaicism in neurofibromatosis type 1

BackgroundNeurofibromatosis type 1 (NF-1) is a tumor predisposition syndrome resulting from mutations in NF1 antioncogene. Differential diagnosis with genetic testing is essential in NF-1 diagnostics due to its clinical variability. Identifying of pathogenic mutations is challenging because of the gene size and structure, especially for low-level somatic mosaicism. Notably, patients with mosaic NF-1 demonstrate no less severe phenotype than those with classic form. Nowadays, NGS and Sanger sequencing are recognized diagnostics methods and they both are not sensitive enough to mosaic genotypes with small fractions of alternative alleles. We believe that this can be resolved with a special approach to sequencing data analysis. MethodsIn order to re-evaluate previously obtained NGS (Ion AmpliSeq technology) results for 275 probands with clinical diagnosis “NF-1” or “NF, unspecified” for whom germline mutations in NF1 and NF2 genes were not identified, we developed an improved data analysis pipeline to search for somatic mutations, which includes: (1) programmatic pool-based division of NGS reads, (2) elimination of out-of-design aligned reads, (3) exclusion of systematic sequencing errors, (4) variant calling with low stringency parameters (alternative allele frequency, AF≥0.05; read depth, DP≥20). Newly detected mutations were verified using Sanger sequencing and heteroduplex analysis. Sanger results were analysed using our in-house SeqBase software, highly sensitive to mosaic variants. ResultsApplication of our NGS data reanalysis algorithm allowed us to detect 12 cases (4.3%) of somatic mosaic mutations among 275 probands otherwise lacking molecular verification of neurofibromatosis diagnosis. The majority of the identified mutations are nonsense or frameshift, with AF ranging from 0.051 to 0.296. Mutations were verified with alternative methods of molecular diagnostics. ConclusionsImproved sequencing data analysis allows to detect NF-1 cases with mosaic genotype in cases unresolved by conventional analysis pipeline. Yet, success rate is strongly dependent upon the fraction of the mutant allele, thus alternative quantitative methods are required for exhaustive NF-1 molecular diagnosis. Legal entity responsible for the studyFederal State Budgetary Institution "Research Centre for Medical Genetics". FundingThe research was carried out within the state assignment of Ministry of Science and Higher Education of the Russian Federation. DisclosureAll authors have declared no conflicts of interest.

Development of a multidisciplinary clinic of neurofibromatosis type 1 and other neurocutaneous disorders in Greece. A 3-year experience

ABSTRACTGiven the complexity of neurocutaneous syndromes, a multidisciplinary approach has been advocated in order to provide optimum care.Subjects and Methods: Retrospective analysis of a cohort of 157 patients during a 3-year period, seen at a newly developed neurocutaneous clinic in a pediatric tertiary care hospital in Athens (Greece); and systematic chart review of the patients diagnosed with neurofibromatosis type 1 during this time period.Results: The most frequent neurocutaneous syndromes were neurofibromatosis type 1 (NF1) in 89 patients and tuberous sclerosis complex in 17. In 20.38% of patients a neurocutaneous syndrome was not confirmed. Approximately 2/3 of the NF1 patients underwent genetic analysis, and for 76.67% of them, a pathogenic mutation on the NF1 gene was revealed. Eighty-one patients manifested with generalized NF1 and eight with mosaic NF1. Dermatological manifestations included café-au-lait macules in all patients, followed by axillary and/or inguinal freckling (n = 57), external plexiform neurofibromas (n = 17), and cutaneous and subcutaneous neurofibromas (n = 11). Approximately half of patients had learning disabilities and attention deficit hyperactivity disorder, followed by mental retardation (n = 9), autistic spectrum disorders (n = 4), headaches (n = 3) and seizures (n = 2). Neuroimaging showed characteristic areas of hyperintensity on T2-weighted images in 74.07% of patients and optic pathway glioma in 19.75%. Two patients developed malignant peripheral sheath nerve tumor.Conclusions: Neurocutaneous syndromes are clinically heterogeneous and the surveillance of potential clinical complications is challenging. The availability of genetic diagnosis and novel imaging methods in this group of disorders is likely to further expand their clinical spectrum. Guidelines for assessment and management will need to be modified based on new available data.

282 Giant café-au-lait macule, plexiform neurofibroma and multiple melanocytic nevi in a patient with mosaic neurofibromatosis type 1 caused by biallelic NF1 microdeletions

282 Giant café-au-lait macule, plexiform neurofibroma and multiple melanocytic nevi in a patient with mosaic neurofibromatosis type 1 caused by biallelic NF1 microdeletions

Early history of the different forms of neurofibromatosis from ancient Egypt to the British Empire and beyond: First descriptions, medical curiosities, misconceptions, landmarks, and the persons behind the syndromes.

The earliest examples of neurofibromatosis (in this case type 1, NF1) can be traced in the Ebers Papyrus (Ancient Egypt, 1.500 B.C.), in a Hellenistic statuette (Smyrna, 323 B.C.), in the coinage of the Parthians kings (247 B.C.) and in some 13th century monks' drawings. These earlier examples are somewhat less well defined as compared to the most recent better defined reports credited as having NF1 including an Inca child mummy (1480-1650 AD), Ulisse Aldrovandi's homuncio ("Monstrorum Historia", 1592 A.D.) with mosaic NF1 or the illustrations seen in the 18th century "Buffon's Histoire Naturelle" and "Cruveilhier's Anatomie Pathologique du Corps Human". The first English language report on NF1 was made by Akenside in 1768 and the first systematic review by Robert William Smith in 1849, while Virchow's pupil, Friedrich Daniel von Recklinghausen, in 1882, was the first to understand the origin of skin tumors and to name them neurofibromas. The touching story of Joseph C. Merrick (the "Elephant man," (who had Proteus syndrome and not NF1), in 1884, played an important role in the later misconception of NF1, as did the novel by Vicotr Hugo on the hunchback Quasimodo. The studies by van der Hoeve (1921), Yakovlev and Guthrie (1931), and Van Bogaert (1935), categorized "von Recklinghausen's" neurofibromatosis among the phakomatoses and the neurocutaneous syndromes. The first known mention of an acoustic neuroma (at autopsy) is attributed to Eduard Sandifort (1777 AD) while John H. Wishart made the earliest autoptic description of neurofibromatosis type 2 (NF2), in 1822, in a 21-year-old man with bilateral acoustic neuromas, who manifested signs since his infancy (Wishart subtype NF2). Smith likely described the first case of schwannomatosis in 1849. Older, Virchow, von Recklinghausen, and Verocay first classified "neuromas" and Masson and Penfield first used the word "schwannoma" taking it from Theodore Schwann's works. In 1903 Henneberg and Koch described NF2 in detail. Young, Eldridge, and Gardner, in the late '70, established NF2 as a distinct familial entity (Gardner subtype NF2). Schwannomatosis, the late entry of the different forms of neurofibromatosis, was credited in the middle '90.

Mosaic Neurofibromatosis Type 1 in Children: A Single-Institution Experience.

Neurofibromatosis type 1 (NF1) is a neurocutaneous disorder caused by loss-of-function mutation in the NF1 gene. Segmental or mosaic NF1 (MNF) is an uncommon presentation of the NF1 result of postzygotic mutations that present with subtle localised clinical findings. Our study's objectives were to describe the clinical characteristics of children with MNF. We conducted a cross-sectional study of children diagnosed with MNF at the Hospital for Sick Children in Toronto, Canada, from January 1992 to September 2012. Data were abstracted from health records and analysed using a standardised data collection form approved by our hospital Research Ethics Board. We identified 60 patients with MNF; 32 of 60 (53.3%) were female. Mean ± SD age at first assessment was 10.6 ± 4.6 years. The most common initial physical manifestation in 39 of 60 (65.0%) patients was localised pigmentary changes only, followed by plexiform neurofibromas only in 10 of 60 (16.7%) and neurofibromas only in 9 of 60 (15.0%). Unilateral findings were seen in 46 of 60 (76.7%) patients. Most common associations identified included learning disabilities (7/60; 12%) and bony abnormalities (6/60; 10.0%). MNF is an underrecognised condition with potential implications for patients. Children mostly present with pigmentary anomalies only. Most patients do not develop associated findings or complications before adulthood, but long-term follow-up will help determine outcomes and possible associations. Recognition and confirmation of the diagnosis is important to provide follow-up and genetic counselling to patients.

Cutaneous and Systemic Findings in Mosaic Neurofibromatosis Type 1.

Mosaic neurofibromatosis type 1 (MNF1) is a variant of neurofibromatosis type 1 (NF1) in which clinical manifestations are limited to one or several body segments. The objective was to characterize the cutaneous features and associated systemic findings in a cohort of children with MNF1. We performed a retrospective study of 40 children diagnosed with MNF1 at the Department of Dermatology, Hospital Infantil Niño Jesús, Madrid, Spain, from January 1, 1986, to October 31, 2015. All patients had pigmentary changes, alone (n = 39) or in combination with neurofibromas (n = 1). Twenty-four cases fulfilling the definition of MNF1 had six or more café au lait spots with or without freckling within the affected segment. They all lacked any other National Institutes of Health criteria of NF1. No patient had juvenile xanthogranuloma (JXG) or nevus anemicus (NA). Two children with MNF1 had epilepsy and two others developed malignancy (Hodgkin's lymphoma and ganglioneuroblastoma). Pigmentary changes are the most frequent presentation of MNF1 in children. MNF1 must be considered with segmentary distribution of freckling and café au lait spots. Other frequent cutaneous findings in NF1, such as JXG or NA, seem to be exceptional in MNF1. Although the possibility of systemic complications and cancer risk seem to be low, patients must be followed up.

Abstract P2-02-02: Clinical significance of TP53 mosaic mutations uncovered in constitutional genetic testing

Abstract Background: Mosaic findings (mutations outside of the expected 50:50 allele ratio) are often detected in the course of routine constitutional genetic testing due to the high sensitivity of next-generation sequencing (NGS) technologies. The significance of these findings is however often unclear. They can result from constitutional mosaicism secondary to an early embryological event, an acquired somatic mutation in hematopoietic cells, a technical artifact, or (less likely) a reversion event. Studies have shown that clonal hematopoiesis increases with age, seen in up to 10% and 25% of individuals 65 and 90 years of age, respectively. Additional studies have demonstrated expansion of TP53 mutations in peripheral blood cells following chemotherapy administration. We therefore wanted to investigate the potential clinical significance of mosaic mutations found in the peripheral blood in samples submitted for hereditary cancer testing with a focus on TP53. Methods: We examined high-depth NGS data from blood cell-derived DNA for mutations with pathogenic potential suggestive of mosaicism (5-30% allele frequency) in known hereditary cancer genes. For each gene, we determined the average ages of patients tested and compared these distributions to the distribution of ages of patients found to have mosaic mutations. For the mosaic TP53 mutations, we further characterized the mutations found as well as described the clinical scenarios in which the mosaic findings occurred. Results: To date, 101 patients were found to have possibly mosaic mutations with pathogenic potential, including 26 cases with TP53 mutations (0.07% of patients tested), 16 with CHEK2 mutations (0.05%), and 16 with ATM mutations (0.05%). Significant bias towards older ages is seen in patients with ATM (p= 0.0026) and CHEK2 (p=4.2x10-6) mosaic findings. Mosaic TP53 and NF1 mutations were also enriched in older patients , although not as significantly as CHEK2 and ATM mosaic patients. 24/25 patients with TP53 mosaic mutations with a known history were cancer affected. In the COSMIC database, 20/20 of the TP53 mosaic mutations are associated with neoplastic conditions and 13/20 are associated with hematolymphoid neoplasms. 15/20 of the pathogenic mosaic TP53 findings were seen previously in our lab at a ratio corresponding to germline, thereby significantly lessening the possibility of technical artifact. Conclusion: The statistically significant older ages of patients with ATM and CHEK2 mosaic variants suggests that many of these are acquired changes in hematopoietic stem cells rather than constitutional mosaicism per se. Although NF1 is known to be associated with constitutional mosaicism, the bias towards older patients of the NF1 mosaics we saw similarly suggests that most are acquired changes in the hematopoietic stem cells. The less significant age bias in the TP53 events suggests that chemotherapy administration may be leading to enrichment of TP53 mutated clones, although an increased rate of constitutional mosaicism cannot be ruled out. Citation Format: Deucher A, Lincoln S, Sorenson J. Clinical significance of TP53 mosaic mutations uncovered in constitutional genetic testing [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-02-02.

Partial unilateral lentiginosis is mosaic neurofibromatosis type 1 or not?

Partial unilateral lentiginosis (PUL) is a rare pigmentation disorder characterized by numerous lentigines with sharp margins in the midline in one or more dermatomes. Its segmental pattern suggests that this presentation accompanied by café-au-lait spots, Lisch nodule or neurofibromas has a close relationship with mosaic neurofibromatosis type 1 or segmental neurofibromatosis (NF) in particular. In a group of 16 patients with PUL, who presented at the dermatology outpatient clinic between 1998 and 2015, an examination was made of consanguineous marriage in the family history, the presence of a similar lesion or NF in first-degree relatives, neurofibroma in the physical examination, the involvement pattern, axillary/inguinal freckling and the presence and number of café-au-lait spots. The ophthalmological examination investigated Lisch nodule and optic glioma. The skeletal system was examined for NF involvement. Of 16 patients, 13 (81.2%) were female and three (18.8%) were male with a mean age of 31.19 years (range, 15-48). There was no family history of PUL in any case. Consanguineous marriage was absent in 15 patients (93.8%). While there were accompanying café-au-lait spots in three patients (18.8%). Lisch nodule was an accompanying finding in three patients (18.8%). Axillary freckling was detected in four (25%) patients. Neurofibroma was found in only one patient. Although café-au-lait spots, axillary freckling, neurofibroma and Lisch nodule were present in a small number of the patients, the presence of the findings may be considered to be specific to NF suggests that PUL is a variant of mosaic NF-1. Genetic studies will help to further elucidate this subject.

An Update on Neurofibromatosis Type 1: Not Just Café-au-Lait Spots and Freckling. Part II. Other Skin Manifestations Characteristic of NF1. NF1 and Cancer

In addition to the classic skin manifestations of NF1 (café-au-lait spots, freckling, and neurofibromas), the presence of other manifestations such as nevus anemicus and juvenile xanthogranuloma may be of high predictive value in patients with an uncertain diagnosis. Localized or mosaic NF1, also known as segmental neurofibromatosis, is caused by a postzygotic mutation responsible for the presence of the typical disease manifestations limited to a body segment. Although no follow-up protocols are available for these patients with mosaic NF1, the risk of complications is much lower than in the generalized forms of the disease. Malignant tumors are, probably, the most feared complication of NF1. In decreasing order, the most frequent neoplasms are optic nerve glioma, malignant peripheral nerve sheath tumor, gastrointestinal stromal tumors, and pheochromocytomas. Most malignant peripheral nerve sheath tumors are the result of malignant transformation of plexiform neurofibromas and early diagnosis is a decisive factor in the prognosis. In conclusion, NF1 is a multisystemic disease that requires multidisciplinary follow-up with dermatologists playing an important role.

Mosaic Neurofibromatosis Type 1: A Systematic Review.

Confusion is widespread regarding segmental or mosaic neurofibromatosis type 1 (MNF1). Physicians should use the same terms and be aware of its comorbidities and risks. The objective of the current study was to identify and synthesize data for cases of MNF1 published from 1977 to 2012 to better understand its significance and associations. After a literature search in PubMed, we reviewed all available relevant articles and abstracted and synthetized the relevant clinical data about manifestations, associated findings, family history and genetic testing. We identified 111 articles reporting 320 individuals. Most had pigmentary changes or neurofibromas only. Individuals with pigmentary changes alone were identified at a younger age. Seventy-six percent had localized MNF1 restricted to one segment; the remainder had generalized MNF1. Of 157 case reports, 29% had complications associated with NF1. In one large case series, 6.5% had offspring with complete NF1. The terms "segmental" and "type V" neurofibromatosis should be abandoned, and the correct term, mosaic NF1 (MNF1), should be used. All individuals with suspected MNF1 should have a complete physical examination, genetic testing of blood and skin, counseling, and health surveillance.

Clinical presentations of 23 half-siblings from a mosaic neurofibromatosis type 1 sperm donor.

The Danish sperm donor number 7042 has fathered several offspring with neurofibromatosis type 1 (NF1) worldwide. NF1 is caused by loss-of-function mutations in the NF1 gene and more than 1000 NF1 mutations are identified. Analysis of the donor sperm demonstrated gonosomal mosaicism with an intragenic deletion involving exons 15-29 in the NF1 gene. At the two Danish reference centres for NF1 patients, we evaluated 23 half-siblings from the donor. Nine were diagnosed with NF1. The severity grade of NF1 progressed from minimal to mild/moderate within 3 years of follow-up. The NF1 phenotype shows great variability in intra- and inter-family expressivity and to date only two NF1 genotype-phenotype correlations have been established. This rare possibility of a long-term follow-up of a cohort of half-siblings with NF1 makes further studies including phenotypic variability and search for modifier genes possible. To achieve this goal, we have initiated The International Donor 7042 NF1 Offspring Registry. Research facilitated via this registry may reveal important new knowledge of clinical characteristics and prognostics for the specific NF1 genotype and thereby contribute to future individualised targeted clinical follow-up and treatment.