Pigment cell-related manifestations in neurofibromatosis type 1: an overview

A Misdiagnosed Familiar Brooke-Spiegler Syndrome: Case Report and Review of the Literature

Aim of the report: Brooke-Spiegler syndrome (BSS) is a rare autosomal dominant disease characterized by the growth of cylindromas, spiradenomas, trichoepitheliomas, or their combination. These neoplasms usually begin in the second decade and progressively increase in number and size over the years. Diagnosis necessitates consideration of family history, clinical examination, histological findings, and genetic analysis. The aim of this paper is to explore the clinical overlap between Brooke-Spiegler syndrome (BSS) and neurofibromatosis type 1 (NF1). We aim to highlight the challenges associated with their differential diagnosis and emphasize the lack of standardized diagnostic criteria and treatment approaches. Case presentation: Hereby, we introduce the case of a 28-year-old male referred for suspicion of neurofibromatosis type 1 (NF1) who initially declined the recommended surgical excision for a scalp mass. After four years, he returned with larger masses of the scalp, and underwent excision of multiple masses, revealing cylindromas, spiradenomas, and spiradenocylindromas. Family history reported similar tumors in his father, who was also diagnosed with NF1 for the presence of multiple subcutaneous lesions on the scalp. Clinical overlap led to a genetic consultation, but testing for CYLD mutations yielded no significant variations. Despite this, the strong family history and consistent findings led to a revised diagnosis of Brooke-Spiegler syndrome, correcting the initial misdiagnosis of NF1 syndrome. Conclusions: Thanks to the evolving landscape of BSS research over the past two decades, its molecular underpinnings, clinical presentation, and histopathological features are now clearer. However, a thorough family history assessment is mandatory when BSS is suspected. It is our belief that a multidisciplinary approach and cooperation between specialists are essential when dealing with BSS. By sharing this case, we hope to underscore the importance of considering BSS as a differential diagnosis, especially in cases with atypical presentations or overlapping features with other syndromes like NF1.

Multispectral Imaging Analysis of Skin Lesions in Patients with Neurofibromatosis Type 1

Neurofibromatosis type 1 (NF1) is a rare disease, affecting around 1 in 3500 individuals in the general population. The rarity of the disease contributes to the scarcity of the available diagnostic and therapeutic approaches. Multispectral imaging is a non-invasive imaging method that shows promise in the diagnosis of various skin diseases. The device utilized for the present study consisted of four sets of narrow-band LEDs, including 526 nm, 663 nm, and 964 nm for diffuse reflectance imaging and 405 nm LEDs, filtered through a 515 nm long-pass filter, for autofluorescence imaging. RGB images were captured using a CMOS camera inside of the device. This paper presents the results of this multispectral skin imaging approach to distinguish the lesions in patients with NF1 from other more common benign skin lesions. The results show that the method provides a potential novel approach to distinguish NF1 lesions from other benign skin lesions.

RETINAL VASCULAR ABNORMALITIES IN CHILDREN WITH NEUROFIBROMATOSIS TYPE 1

PURPOSE

Retinal vascular abnormalities (RVAs) have been recently described in patients with neurofibromatosis Type 1 (NF1) as vascular tortuosity, best visible on infrared imaging. This study assessed clinical RVA's characteristics in a large series of children with NF1.

METHODS

This retrospective observational study was conducted in children (0-18 years) with an NF1 diagnosis. Using near-infrared imaging, RVAs were classified according to the nature of vessels involvement and their degree of tortuosity.

RESULTS

Retinal imaging from 140 children, with a median age of 8.8 years (1.5-18), was included; 52 patients (37.1%) (81 eyes) exhibited RVAs. These RVAs comprised 96% (50/52) of simple vascular tortuosity and 17% (9/52) of a corkscrew pattern. A corkscrew pattern involved only small veins, whereas simple vascular tortuosity could affect both arteries and veins. No statistically significant age correlation was observed, but evolution of RVAs from simple vascular tortuosity to corkscrew pattern was observed in 5 cases.

CONCLUSION

Retinal vascular abnormalities occurred in 37.1% of children with NF1. These abnormalities may result from NF1 promoting localized tortuosity in both small arteries and veins, whereas only small second-order or tertiary-order venules evolve to a highly tortuous pattern.

Nerve-associated Schwann cell precursors contribute extracutaneous melanocytes to the heart, inner ear, supraorbital locations and brain meninges

Melanocytes are pigmented cells residing mostly in the skin and hair follicles of vertebrates, where they contribute to colouration and protection against UV-B radiation. However, the spectrum of their functions reaches far beyond that. For instance, these pigment-producing cells are found inside the inner ear, where they contribute to the hearing function, and in the heart, where they are involved in the electrical conductivity and support the stiffness of cardiac valves. The embryonic origin of such extracutaneous melanocytes is not clear. We took advantage of lineage-tracing experiments combined with 3D visualizations and gene knockout strategies to address this long-standing question. We revealed that Schwann cell precursors are recruited from the local innervation during embryonic development and give rise to extracutaneous melanocytes in the heart, brain meninges, inner ear, and other locations. In embryos with a knockout of the EdnrB receptor, a condition imitating Waardenburg syndrome, we observed only nerve-associated melanoblasts, which failed to detach from the nerves and to enter the inner ear. Finally, we looked into the evolutionary aspects of extracutaneous melanocytes and found that pigment cells are associated mainly with nerves and blood vessels in amphibians and fish. This new knowledge of the nerve-dependent origin of extracutaneous pigment cells might be directly relevant to the formation of extracutaneous melanoma in humans.

Severe Phenotype in Patients with Large Deletions of NF1

Complete deletion of the NF1 gene is identified in 5-10% of patients with neurofibromatosis type 1 (NF1). Several studies have previously described particularly severe forms of the disease in NF1 patients with deletion of the NF1 locus, but comprehensive descriptions of large cohorts are still missing to fully characterize this contiguous gene syndrome. NF1-deleted patients were enrolled and phenotypically characterized with a standardized questionnaire between 2005 and 2020 from a large French NF1 cohort. Statistical analyses for main NF1-associated symptoms were performed versus an NF1 reference population. A deletion of the NF1 gene was detected in 4% (139/3479) of molecularly confirmed NF1 index cases. The median age of the group at clinical investigations was 21 years old. A comprehensive clinical assessment showed that 93% (116/126) of NF1-deleted patients fulfilled the NIH criteria for NF1. More than half had café-au-lait spots, skinfold freckling, Lisch nodules, neurofibromas, neurological abnormalities, and cognitive impairment or learning disabilities. Comparison with previously described "classic" NF1 cohorts showed a significantly higher proportion of symptomatic spinal neurofibromas, dysmorphism, learning disabilities, malignancies, and skeletal and cardiovascular abnormalities in the NF1-deleted group. We described the largest NF1-deleted cohort to date and clarified the more severe phenotype observed in these patients.

Genotype-Phenotype Correlations in Neurofibromatosis Type 1: A Single-Center Cohort Study

Simple Summary

Neurofibromatosis type 1 (NF1) is a complex disorder characterized by a multisystem involvement and cancer predisposition. It is caused by genetic variants in NF1, a large tumor suppressor gene encoding a cytoplasmatic protein (neurofibromin) with a regulatory role in essential cellular processes. Genotype–phenotype correlations in NF1 patients are so far elusive. We retrospectively reviewed clinical, radiological, and genetic data of 583 individuals with at least 1 National Institutes of Health (NIH) criterion for NF1 diagnosis, including 365 subjects fulfilling criteria for the diagnosis. Novel genotype–phenotype correlations were identified through uni- and multivariate statistical analysis. Missense variants negatively correlated with neurofibromas. Skeletal abnormalities were associated with frameshift variants and whole gene deletions. The c.3721C>T; p.(R1241*) variant positively correlated with structural brain alterations, whereas the c.6855C>A; p.(Y2285*) variant was associated with a higher prevalence of Lisch nodules and endocrinological disorders. These novel NF1 genotype–phenotype correlations may have a relevant role in the implementation of patients’ care.

Abstract

Neurofibromatosis type 1 (NF1) is a proteiform genetic condition caused by pathogenic variants in NF1 and characterized by a heterogeneous phenotypic presentation. Relevant genotype–phenotype correlations have recently emerged, but only few pertinent studies are available. We retrospectively reviewed clinical, instrumental, and genetic data from a cohort of 583 individuals meeting at least 1 diagnostic National Institutes of Health (NIH) criterion for NF1. Of these, 365 subjects fulfilled ≥2 NIH criteria, including 235 pediatric patients. Genetic testing was performed through cDNA-based sequencing, Next Generation Sequencing (NGS), and Multiplex Ligation-dependent Probe Amplification (MLPA). Uni- and multivariate statistical analysis was used to investigate genotype–phenotype correlations. Among patients fulfilling ≥ 2 NIH criteria, causative single nucleotide variants (SNVs) and copy number variations (CNVs) were detected in 267/365 (73.2%) and 20/365 (5.5%) cases. Missense variants negatively correlated with neurofibromas (p = 0.005). Skeletal abnormalities were associated with whole gene deletions (p = 0.05) and frameshift variants (p = 0.006). The c.3721C>T; p.(R1241*) variant positively correlated with structural brain alterations (p = 0.031), whereas Lisch nodules (p = 0.05) and endocrinological disorders (p = 0.043) were associated with the c.6855C>A; p.(Y2285*) variant. We identified novel NF1 genotype–phenotype correlations and provided an overview of known associations, supporting their potential relevance in the implementation of patient management.

Hyperpigmented spots at fundus examination: a new ocular sign in Neurofibromatosis Type I

BACKGROUND

Neurofibromatosis Type I (NF1), also termed von Recklinghausen disease, is a rare genetic disorder that is transmitted by autosomal dominant inheritance, with complete penetrance and variable expressivity. It is caused by mutation in the NF1 gene on chromosome 17 encoding for neurofibromin, a protein with oncosuppressive activity, and it is 50% sporadic or inherited. The disease is characterized by a broad spectrum of clinical manifestations, mainly involving the nervous system, the eye and skin, and a predisposition to develop multiple benign and malignant neoplasms. Ocular diagnostic hallmarks of NF1 include optic gliomas, iris Lisch nodules, orbital and eyelid neurofibromas, eyelid café-au-lait spots. Choroidal nodules and microvascular abnormalities have recently been identified as additional NF1-related ocular manifestations. The present study was designed to describe the features and clinical significance of a new sign related to the visual apparatus in NF-1, represented by hyperpigmented spots (HSs) of the fundus oculi.

RESULTS

HSs were detected in 60 (24.1%) out of 249 patients with NF1, with a positive predictive value of 100% and a negative predictive value of 44.2%. None of the healthy subjects (150 subjects) showed the presence of HSs. HSs were visible under indirect ophthalmoscopy, ultra-wide field (UWF) pseudocolor imaging and red-only laser image, near-infrared reflectance (NIR)-OCT, but they were not appreciable on UWF green reflectance. The location and features of pigmentary lesions matched with the already studied NF1-related choroidal nodules. No significant difference was found between the group of patients (n = 60) with ocular HSs and the group of patients (n = 189) without ocular pigmented spots in terms of age, gender or severity grading of the disease. A statistically significant association was demonstrated between the presence of HSs and neurofibromas (p = 0.047), and between the presence of HSs and NF1-related retinal microvascular abnormalities (p = 0.017).

CONCLUSIONS

We described a new ocular sign represented by HSs of the fundus in NF1. The presence of HSs was not a negative prognostic factor of the disease. Following multimodal imaging, we demonstrated that HSs and choroidal nodules were consistent with the same type of lesion, and simple indirect ophthalmoscopy allowed for screening of HSs in NF1.

Challenges in staging and surveillance of patients with neurofibromatosis and cutaneous malignant melanoma

Malignant melanoma is a skin neoplasm with a rising trend of incidence. Positron Emission Tomography in combination with Computed Tomography (PET-CT) imaging is an essential diagnostic tool for both staging and surveillance of melanoma patients; especially in metastatic disease, where prognosis is poor. We report a case of a patient with known Neurofibromatosis type 1 (NF-1) who presented to the Skin Cancer Multidisciplinary meeting with 11 mm Breslow thickness malignant melanoma of the left forearm. His extensive dermal neurofibromatoses proved a diagnostic challenge to the team. There have been published studies linking NF-1 with malignant melanoma. However the incidence and significance of this has yet to be established. We also discuss the use of PET-CT imaging and skin surveillance in the monitoring and staging of this patient.

Neurofibromatosis type 1 and melanoma of the iris arising from a dysplastic nevus: A rare yet casual association?

PURPOSE

We investigated the molecular causes of an unusual pigmented and ulcerated iris lesion detected in a patient diagnosed with neurofibromatosis type 1 (NF1).

CASE REPORT

A 52-year-old man was referred to our clinic with a non-traumatic ulcer in his left eye. Hyphema reabsorption disclosed a pigmented iris mass, thus ultrasound biomicroscopy and anterior segment fluorescein angiography were performed to investigate for the presence of a malignant lesion. Upon angiography, the lesion appeared highly vascularized but prevented posterior iris examination. Therefore, a gonioscopy was executed revealing extension of the lesion into the peripheral iris. Histopathology of the excisional iris biopsy revealed iris melanoma over a dysplastic nevus. NF1 is an autosomal dominant disorder characterized by pigmented cutaneous lesions, multiple skin tumors, and spinal and cranial nerve tumors. Uveal melanoma is the most common primary intraocular malignancy in adults. Up to 92% of cutaneous melanomas occur in patients with dysplastic nevus syndrome. Skin melanomas have been found in 0.1%-5.4% of NF1 patients. In literature, only 18 reports of uveal melanoma have been documented in association with NF1, including three cases of iris melanoma.

RESULTS

NF1 gene testing identified a causative mutation in the germline but no loss of the wild-type allele in the iris melanoma.

CONCLUSIONS

Occurrence of both diseases in one patient is extremely rare, but the common origin of Schwann cells and melanoblasts suggests a non-casual association. Therefore, we propose that NF1 patients should be screened for nevi, both cutaneous and uveal, for better patients' management.

Hyperpigmentation of the hard palate mucosa in a patient with chronic myeloid leukaemia taking imatinib

Background

Imatinib mesylate is an inhibitor of the tyrosine kinase Bcr–Abl and a first-line treatment for Philadelphia chromosome-positive chronic myeloid leukaemia (CML). Dermatological side effects include superficial oedema, pustular eruption, lichenoid reactions, erythroderma, and skin rash. Depigmentation of the skin and/or mucosa is uncommon, and hyperpigmentation is rare.

Case presentation

We present the case of a 63-year-old Caucasian male with widespread hyperpigmentation of the hard palate associated with a 9-year history of imatinib therapy to treat CML. He did not complain of any symptoms. Clinical examination did not reveal any abnormal pigmentation of the skin or other region of the oral mucosa. He did not smoke cigarettes or drink alcohol. His medication regimen was a proton pump inhibitor, a beta-blocker, cardioaspirin, atorvastatin, and imatinib 400 mg/day. Histopathologically, melanin and haemosiderin deposits were evident in the lamina propria. The lesion persisted, with no clinical change, through several follow-ups. We reviewed the literature to explore the possible relationship between oral hyperpigmentation and long-term imatinib mesylate treatment.

Conclusions

We diagnosed oral pigmentation associated with imatinib intake based on the medical history and clinical features of the pigmented macules. Oral pigmentation may have a variety of causes, and differential diagnosis requires nodal analysis. Clinicians should be aware of possible oral mucosal hyperpigmentation in patients taking imatinib mesylate. Such pigmentation is benign and no treatment is needed, but surveillance is advisable.

Ophthalmic manifestations in neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is a relatively common multisystemic inherited disease and has been extensively studied by multiple disciplines. Although genetic testing and confirmation are available, NF1 remains a clinical diagnosis. Many manifestations of NF1 involve the eye and orbit, and the ophthalmologist, therefore, plays a significant role in the diagnosis and treatment of NF1 patients. Improvements in diagnostic and imaging instruments have provided new insight to study the ophthalmic manifestations of the disease. We provide a comprehensive and up-to-date overview of the ocular and orbital manifestations of NF1.

An Optimized Approach to Recover Secreted Proteins from Fibroblast Conditioned-Media for Secretomic Analysis

The proteins secreted by a particular type of cell, the secretome, play important roles in the regulation of many physiological processes via paracrine/autocrine mechanisms, and they are of increasing interest to help understanding rare diseases and to identify potential biomarkers and therapeutic targets. To facilitate ongoing research involving secreted proteins, we revisited cell culture protocols and whole secreted protein enrichment protocols. A reliable method for culturing and precipitating secreted protein from patient-derived fibroblast conditioned-medium was established. The method is based on the optimization of cell confluency and incubation time conditions. The well-established carrier-based TCA-DOC protein precipitation method was consistently found to give higher protein recovery yield. According to our results, we therefore propose that protein enrichment should be performed by TCA-DOC precipitation method after 48 h at 95% of confluence in a serum-deprived culture medium. Given the importance of secreted proteins as a source to elucidate the pathogenesis of rare diseases, especially neurological disorders, this approach may help to discover novel candidate biomarkers with potential clinical significance.

In vitro modeling of hyperpigmentation associated to neurofibromatosis type 1 using melanocytes derived from human embryonic stem cells

"Café-au-lait" macules (CALMs) and overall skin hyperpigmentation are early hallmarks of neurofibromatosis type 1 (NF1). One of the most frequent monogenic diseases, NF1 has subsequently been characterized with numerous benign Schwann cell-derived tumors. It is well established that neurofibromin, the NF1 gene product, is an antioncogene that down-regulates the RAS oncogene. In contrast, the molecular mechanisms associated with alteration of skin pigmentation have remained elusive. We have reassessed this issue by differentiating human embryonic stem cells into melanocytes. In the present study, we demonstrate that NF1 melanocytes reproduce the hyperpigmentation phenotype in vitro, and further characterize the link between loss of heterozygosity and the typical CALMs that appear over the general hyperpigmentation. Molecular mechanisms associated with these pathological phenotypes correlate with an increased activity of cAMP-mediated PKA and ERK1/2 signaling pathways, leading to overexpression of the transcription factor MITF and of the melanogenic enzymes tyrosinase and dopachrome tautomerase, all major players in melanogenesis. Finally, the hyperpigmentation phenotype can be rescued using specific inhibitors of these signaling pathways. These results open avenues for deciphering the pathological mechanisms involved in pigmentation diseases, and provide a robust assay for the development of new strategies for treating these diseases.

NF1 loss induces senescence during human melanocyte differentiation in an iPSC-based model

Neurofibromatosis type 1 (NF1) is a frequent genetic disease leading to the development of Schwann cell-derived neurofibromas or melanocytic lesions called café-au-lait macules (CALMs). The molecular mechanisms involved in CALMs formation remain largely unknown. In this report, we show for the first time pathophysiological mechanisms of abnormal melanocyte differentiation in a human NF1(+/-) -induced pluripotent stem cell (iPSC)-based model. We demonstrate that NF1 patient-derived fibroblasts can be successfully reprogrammed in NF1(+/-) iPSCs with active RAS signaling and that NF1 loss induces senescence during melanocyte differentiation as well as in patient's-derived CALMs, revealing a new role for NF1 in the melanocyte lineage.

Elucidating distinct roles for NF1 in melanomagenesis

BRAF mutations play a well-established role in melanomagenesis; however, without additional genetic alterations, tumor development is restricted by oncogene-induced senescence (OIS). Here, we show that mutations in the NF1 tumor suppressor gene cooperate with BRAF mutations in melanomagenesis by preventing OIS. In a genetically engineered mouse model, Nf1 mutations suppress Braf-induced senescence, promote melanocyte hyperproliferation, and enhance melanoma development. Nf1 mutations function by deregulating both phosphoinositide 3-kinase and extracellular signal-regulated kinase pathways. As such, Nf1/Braf-mutant tumors are resistant to BRAF inhibitors but are sensitive to combined inhibition of mitogen-activated protein/extracellular signal-regulated kinase kinase and mTOR. Importantly, NF1 is mutated or suppressed in human melanomas that harbor concurrent BRAF mutations, NF1 ablation decreases the sensitivity of melanoma cell lines to BRAF inhibitors, and NF1 is lost in tumors from patients following treatment with these agents. Collectively, these studies provide mechanistic insight into how NF1 cooperates with BRAF mutations in melanoma and show that NF1/neurofibromin inactivation may have an impact on responses to targeted therapies.

Partial Blindness to Submicron Topography in NF1 Haploinsufficient Cultured Fibroblasts Indicates a New Function of Neurofibromin in Regulation of Mechanosensoric

Cells sense physical properties of their extracellular environment and translate them into biochemical signals. In this study, cell responses to surfaces with submicron topographies were investigated in cultured human NF1 haploinsufficient fibroblasts. Age-matched fibroblasts from 8 patients with neurofibromatosis type 1 (NF1(+/-)) and 9 controls (NF1(+/+)) were cultured on surfaces with grooves of 200 nm height and lateral distance of 2 μm. As cellular response indicator, the mean cell orientation along microstructured grooves was systematically examined. The tested NF1 haploinsufficient fibroblasts were significantly less affected by the topography than those from healthy donors. Incubation of the NF1(+/-) fibroblasts with the farnesyltransferase inhibitor FTI-277 and other inhibitors of the neurofibromin pathway ameliorates significantly the cell orientation. These data indicate that NF1 haploinsufficiency results in an altered response to specific surface topography in fibroblasts. We suggest a new function of neurofibromin in the sensoric mechanism to topographies and a partial mechanosensoric blindness by NF1 haploinsufficiency.

Mucosal pigmentation caused by imatinib: report of three cases

Imatinib mesylate (STI-571, Gleevec(®)), a tyrosine kinase inhibitor, is a first-line medication for treating chronic myeloid leukemia (CML). Clinical studies revealed very good hematological responses without significant side effects. However, imatinib may lead to mucosal pigmentation. Three patients, two males aged 64 and 53 and one female aged 29 presented with a painless, diffuse, grey-blue pigmentation of the mucosa of the hard palate. Both male patients had a history of CML and had been on imatinib for 4 and 10 years, respectively. The female patient had been on imatinib for 4 years for pelvic fibromatosis. Histopathologically, deposition of fine, dark-brown, spherical granules was noted within the connective tissue. There was no inflammation or hemorrhage, and no melanosis or melanocytic hyperplasia in the epithelium. The granules stained positively for both Fontana-Masson and Prussian blue stains. Imatinib-induced pigmentation is similar to that caused by other medications such as minocycline and anti-malarial medications, namely the deposition of a drug metabolite containing melanin and iron.

Evolving pattern with age of cutaneous signs in neurofibromatosis type 1: a cross-sectional study of 728 patients

BACKGROUND

Neurofibromatosis type 1 is fully penetrant by the age of 8 years, and 3 criteria of diagnosis are dermatological: café-au-lait spots (CLS), intertriginous freckling and neurofibromas (NF).

OBJECTIVES

The aim of our study was to determine the evolving pattern of cutaneous manifestations during adulthood.

METHODS

Phenotypic data of patients seen in our center between March 2003 and December 2009 were studied. Patients were classified in 10-year groups. Following clinical characteristics, the number of CLS and the number of cutaneous and subcutaneous NF were compared according to age.

RESULTS

728 subjects, 404 females and 324 males (mean age of 32.4 years, range 6-80 years) were studied. Four hundred eighty-nine patients were over 20 years old (67%). The number of CLS (small or large) was significantly decreased with age while the number of cutaneous and subcutaneous NF was strongly increased (p < 0.001).

CONCLUSIONS

The decrease in CLS with age has not been previously reported while an increase in the number of NF is well described during puberty and pregnancy and with age.

Transmembrane potential of GlyCl-expressing instructor cells induces a neoplastic-like conversion of melanocytes via a serotonergic pathway

Understanding the mechanisms that coordinate stem cell behavior within the host is a high priority for developmental biology, regenerative medicine and oncology. Endogenous ion currents and voltage gradients function alongside biochemical cues during pattern formation and tumor suppression, but it is not known whether bioelectrical signals are involved in the control of stem cell progeny in vivo. We studied Xenopus laevis neural crest, an embryonic stem cell population that gives rise to many cell types, including melanocytes, and contributes to the morphogenesis of the face, heart and other complex structures. To investigate how depolarization of transmembrane potential of cells in the neural crest's environment influences its function in vivo, we manipulated the activity of the native glycine receptor chloride channel (GlyCl). Molecular-genetic depolarization of a sparse, widely distributed set of GlyCl-expressing cells non-cell-autonomously induces a neoplastic-like phenotype in melanocytes: they overproliferate, acquire an arborized cell shape and migrate inappropriately, colonizing numerous tissues in a metalloprotease-dependent fashion. A similar effect was observed in human melanocytes in culture. Depolarization of GlyCl-expressing cells induces these drastic changes in melanocyte behavior via a serotonin-transporter-dependent increase of extracellular serotonin (5-HT). These data reveal GlyCl as a molecular marker of a sparse and heretofore unknown cell population with the ability to specifically instruct neural crest derivatives, suggest transmembrane potential as a tractable signaling modality by which somatic cells can control stem cell behavior at considerable distance, identify a new biophysical aspect of the environment that confers a neoplastic-like phenotype upon stem cell progeny, reveal a pre-neural role for serotonin and its transporter, and suggest a novel strategy for manipulating stem cell behavior.

Glial versus melanocyte cell fate choice: Schwann cell precursors as a cellular origin of melanocytes

Melanocytes and Schwann cells are derived from the multipotent population of neural crest cells. Although both cell types were thought to be generated through completely distinct pathways and molecular processes, a recent study has revealed that these different cell types are intimately interconnected far beyond previously postulated limits in that they share a common post-neural crest progenitor, i.e. the Schwann cell precursor. This finding raises interesting questions about the lineage relationships of hitherto unrelated cell types such as melanocytes and Schwann cells, and may provide clinical insights into mechanisms of pigmentation disorders and for cancer involving Schwann cells and melanocytes.

Inherited cancer syndromes in children and young adults

Geneticists estimate that 5% to 10% of all cancers diagnosed in the pediatric age range occur in children born with a genetic mutation that directly increases their lifetime risk for neoplasia. However, despite the fact that only a fraction of cancers in children occur as a result of an identified inherited predisposition, characterizing genetic mutations responsible for increased cancer risk in such syndromes has resulted in a profound understanding of relevant molecular pathways involved in carcinogenesis and/or resistance to neoplasia. Importantly, because most cancer predisposition syndromes result in an increased risk of a small number of defined malignancies, personalized prophylactic surveillance and preventive measures can be implemented in affected patients. Lastly, many of the same genetic targets identified from cancer-prone families are mechanistically involved in the majority of sporadic cancers in adults and children, thereby underscoring the clinical relevance of knowledge gained from these defined syndromes and introducing novel therapeutic opportunities to the broader oncologic community. This review highlights the clinical and genetic features of many of the known constitutional genetic syndromes that predispose to malignancy in children and young adults.

Neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is an autosomal dominant, multisystem disorder affecting approximately 1 in 3500 people. Significant advances in the understanding of the pathophysiology of NF1 have been made in the last decade. While no medical therapies for NF1 are currently available, trials are ongoing to discover and test medical treatments for the various manifestations of NF1, primarily plexiform neurofibromas, learning disabilities, and optic pathway gliomas. In addition, mutational analysis has become available on a clinical basis and is useful for diagnostic confirmation in individuals who do not fulfill diagnostic criteria or when a prenatal diagnosis is desired. There are several disorders that may share overlapping features with NF1; in 2007, a disorder with cutaneous findings similar to NF1 was described. This paper addresses the dermatologist's role in diagnosis and management of NF1 and describes the variety of cutaneous and extracutaneous findings in NF1 to which the dermatologist may be exposed.

LEARNING OBJECTIVES

After completing this learning activity, participants should be able to discuss the indications and limitations of genetic testing in neurofibromatosis type 1, distinguish common and uncommon cutaneous findings, and recognize the dermatologist's role in diagnosis and management.

Surgical Considerations for the Familial Cancer Syndrome, Neurofibromatosis 1: A Comprehensive Review

Neurofibromatosis 1 is one of the more common in heritable disorders that surgeons may encounter. A plethora of systemic associations, both benign and malignant, can affect these patients, and an acute awareness of these associations is essential for proper surgical care. A complete review of this disorder from the surgical perspective follows, highlighting the importance of this awareness. A brief review on the management and follow-up of surgical malignancies associated with this disorder is included.

Multipotent skin-derived precursors: adult neural crest-related precursors with therapeutic potential

We previously made the surprising finding that cultures of multipotent precursors can be grown from the dermis of neonatal and adult mammalian skin. These skin-derived precursors (SKPs) display multi-lineage differentiation potential, producing both neural and mesodermal progeny in vitro, and are an apparently novel precursor cell type that is distinct from other known precursors within the skin. In this review, we begin by placing these findings within the context of the rapidly evolving stem cell field. We then describe our recent efforts focused on understanding the developmental biology of SKPs, discussing the idea that SKPs are neural crest-related precursors that (i) migrate into the skin during embryogenesis, (ii) persist within a specific dermal niche, and (iii) play a key role in the normal physiology, and potentially pathology, of the skin. We conclude by highlighting some of the therapeutic implications and unresolved questions raised by these studies.

Neurofibromatosis type I: genetics and clinical manifestations

Neurofibromatosis type I is multisystem disorder with myriad manifestations, many of which involve the eye. Diagnostic findings include neurofibromas, lisch nodules, café-au-lait macules, freckling, optic pathway gliomas, and skeletal dysplasia. The responsible gene and its protein product, neurofibromin have been identified. Advances have been made in the understanding of the functions of neurofibromin. This has allowed better understanding of the many manifestations and will help identify potential treatments.

Dysplastic nevi with an underlying or juxtaposed neurofibroma: does a relationship exist?

BACKGROUND

Neurofibromas and dysplastic nevi are both common skin disorders found in the general population. The cells in both of these neoplasms are derived from neural crest. There are no published reports of these two lesions occurring in juxtaposition.

OBJECTIVE

We report, for the first time, three cases of dysplastic nevi in spatial association with a neurofibroma that occurred in unrelated individuals.

METHODS AND RESULTS

Three cases of dysplastic nevi occurring in association with solitary neurofibromas were selected prospectively from the routine accessions from August 1, 2003, to July 31, 2005. In none of the three cases, was a dysplastic nevus suspected by the clinician.

CONCLUSION

The finding of dysplastic nevi in a spatial relationship to a neurofibroma is not happenstance since they are both of neural crest cell origin and respond to the same growth factors. It is our belief that these lesions are related and may occur together more often than reported.

Fatal malignant melanoma in a child with neurofibromatosis type 1

Neurofibromatosis type 1 is an autosomal dominant disease and is considered one of the most commonly inherited diseases in humans. Malignant melanoma has been reported in up to 5% of patients with neurofibromatosis type 1. We report a young Saudi boy with neurofibromatosis type 1 who developed fatal metastatic malignant melanoma arising from giant melanocytic nevi within speckled lentiginous nevus (SLN).

Stephen L. Gans Distinguished Overseas Lecture. The neural crest in pediatric surgery

AIM

This review highlights the relevance of the neural crest (NC) as a developmental control mechanism involved in several pediatric surgical conditions and the investigative interest of following some of its known signaling pathways.

METHODS

The participation of the NC in facial clefts, ear defects, branchial fistulae and cysts, heart outflow tract and aortic arch anomalies, pigmentary disorders, abnormal enteric innervation, neural tumors, hemangiomas, and vascular anomalies is briefly reviewed. Then, the literature on clinical and experimental esophageal atresia-tracheoesophageal fistula (EA-TEF) and congenital diaphragmatic hernia (CDH) is reviewed for the presence of associated NC defects. Finally, some of the molecular signaling pathways involved in both conditions (sonic hedgehog, Hox genes, and retinoids) are summarized.

RESULTS

The association of facial, cardiovascular, thymic, parathyroid, and C-cell defects together with anomalies of extrinsic and intrinsic esophageal innervation in babies and/or animals with both EA-TEF and CDH strongly supports the hypothesis that NC is involved in the pathogenesis of these malformative clusters. On the other hand, both EA-TEF and CDH are observed in mice mutant for genes involved in the previously mentioned signaling pathways.

CONCLUSIONS

The investigation of NC-related molecular pathogenic pathways involved in malformative associations like EA-TEF and CDH that are induced by chromosomal anomalies, chemical teratogens, and engineered mutations is a promising way of clarifying why and how some pediatric surgical conditions occur. Pediatric surgeons should be actively involved in these investigations.

Pigmented plexiform neurofibroma: Distinction from a large congenital melanocytic nevus

The substantial clinical and histologic overlap between neurotized congenital melanocytic nevi and the subset of plexiform neurofibromas with hyperpigmentation and hypertrichosis of the overlying skin (pigmented neurofibroma) has led to considerable confusion in the literature. A dark-brown, hypertrichotic plaque covered much of the right lower aspect of the trunk of a 1-year-old girl with a diffuse and plexiform neurofibroma in the same area, numerous café-au-lait macules, and intertriginous freckling. The latter findings were diagnostic of neurofibromatosis-1, which was further supported by the presence of unidentified bright objects on magnetic resonance imaging of the brain. Histologic examination of the hyperpigmented plaque revealed melanocytic hyperplasia at the dermoepidermal junction and a proliferation of rounded, pigmented melanocytes dispersed individually and in occasional small nests in the papillary dermis and scattered within underlying neurofibromatous tissue. Immunohistochemical staining with A103 (Melan-A/MART-1) and PNL2 confirmed the melanocytic differentiation of the pigmented cells, whereas glial fibrillary acidic protein and Leu-7 were detected only within plexiform areas and slender neuroid spindle cells. This case draws attention to the pigmented neurofibroma as a distinct clinicopathologic entity resulting from proliferation of melanocytes and neurosustentacular cells in the setting of neurofibromatosis-1.

Refractive errors in neurofibromatosis type 1 and type 2

OBJECTIVE

To document the prevalence of refractive errors in patients with neurofibromatosis type 1 (NF1) and type 2 (NF2) and to compare it with that of age- and sex-matched controls.

METHODS

82 patients with NF1, 21 patients with NF2 and 103 age- and sex-matched controls were evaluated in this prospective observational case-control study. Cycloplegic autorefraction and dilated fundus examination were performed. Myopia was defined as the spherical equivalent refraction of at least -0.50 diopters (D), hyperopia as the spherical equivalent refraction of at least 2.0 D and astigmatism as the cylinder of at least 1.0 D. Main outcome measures were refractive error, IQ, years of education, height, weight and body mass index (BMI).

RESULTS

The prevalence of myopia was 23.1% in patients with NF1, 23.8% in patients with NF2 and 16.5% in age- and sex-matched controls. These differences were significant (p<0.03, p<0.03), and adjusting for intelligence, education, height, weight and BMI increased the significance of this finding (p<0.001, p<0.001). The prevalences of astigmatism and hyperopia were similar in both groups.

CONCLUSION

A high prevalence of myopia seems to be an additional feature of NF1 and NF2.

Induction of melanocytes from embryonic stem cells and their therapeutic potential

Embryonic stem (ES) cells from many organisms have the capacity to generate in vitro a wide variety of cell types depending on their environment. Understanding precisely how such toti- or pluripotent cells may be driven towards a specific lineage represents a major challenge if our ambition of using ES cells to generate a ready supply of healthy cells for cell-based therapies for a range of diseases is to be realized. Recent advances have demonstrated that melanocytes and retinal pigmented epithelial (RPE) cells exhibiting the characteristics of their natural counterparts can be induced from undifferentiated ES cells grown on monolayers of specific stromal cell lines or by using a combination of Wnt3a, Endothelin-3 and SCF. The ability to induce pigment cells from ES cells promises to facilitate our understanding of the precise molecular mechanisms underlying this process and moreover enable us to distinguish the program of gene expression that underpins the choice made between generating a nerual crest-type melanocyte versus an RPE cell. Moreover, once the combination of signals required to induce a particular type of pigment cell are characterized, the way may be open for future cell-based therapy for various diseases caused by defective pigment cells.

Somatic deletion of the NF1 gene in a neurofibromatosis type 1-associated malignant melanoma demonstrated by digital PCR

Background

Neurofibromatosis type 1 (NF1) is the most common hereditary neurocutaneous disorder and it is associated with an elevated risk for malignant tumors of tissues derived from neural crest cells. The NF1 gene is considered a tumor suppressor gene and inactivation of both copies can be found in NF1-associated benign and malignant tumors. Melanocytes also derive from neural crest cells but melanoma incidence is not markedly elevated in NF1. In this study we could analyze a typical superficial spreading melanoma of a 15-year-old boy with NF1 for loss of heterozygosity (LOH) within the NF1 gene. Neurofibromatosis in this patient was transmitted by the boy's farther who carried the mutation NF1 c. 5546 G/A.

Results

Melanoma cells were isolated from formalin-fixed tissue by liquid coverslip laser microdissection. In order to obtain statistically significant LOH data, digital PCR was performed at the intragenic microsatellite IVS27AC28 with DNA of approx. 3500 melanoma cells. Digital PCR detected 23 paternal alleles and one maternal allele. Statistical analysis by SPRT confirmed significance of the maternal allele loss.

Conclusion

To our knowledge, this is the first molecular evidence of inactivation of both copies of the NF1 gene in a typical superficial spreading melanoma of a patient with NF1. The classical double-hit inactivation of the NF1 gene suggests that the NF1 genetic background promoted melanoma genesis in this patient.

Neurofibromatosis type 1 protein and amyloid precursor protein interact in normal human melanocytes and colocalize with melanosomes

The neurofibromatosis type 1 (NF1) gene product, neurofibromin, is known to interact with Ras, thereby negatively regulating its growth-promoting function. Although this is a well-established interaction, the discovery of other neurofibromin interacting partners could reveal new functional properties of this large protein. Using yeast two-hybrid analysis against a brain cDNA library, we identified a novel interaction between the amyloid precursor protein and the GTPase activating protein-related domain of neurofibromin. This interaction was further analyzed in human melanocytes and confirmed by immunoprecipitation and colocalization studies. In addition, we observed a colocalization of amyloid precursor protein and neurofibromin with melanosomes. Amyloid precursor protein has been proposed to function as a vesicle cargo receptor for the motor protein kinesin-1 in neurons. This colocalization of amyloid precursor protein and neurofibromin with melanosomes was lost in melanocytes obtained from normal skin of a NF1 patient. We suggest that a complex between amyloid precursor protein, neurofibromin, and melanosomes might be important in melanosome transport, which could shed a new light on the etiopathogenesis of pigment-cell-related manifestations in NF1.

Gene expression profiling of cultured human NF1 heterozygous (NF1+/-) melanocytes reveals downregulation of a transcriptional cis-regulatory network mediating activation of the melanocyte-specific dopachrome tautomerase (DCT) gene

One of the major primary features of the neurocutaneous genetic disorder Neurofibromatosis type 1 are the hyperpigmentary café-au-lait macules where disregulation of melanocyte biology is supposed to play a key etiopathogenic role. To gain better insight into the possible role of the tumor suppressor gene NF1, a transcriptomic microarray analysis was performed on human NF1 heterozygous (NF1+/-) melanocytes of a Neurofibromatosis type 1 patient and NF1 wild type (NF1+/+) melanocytes of a healthy control patient, both cultured from normally pigmented skin and hyperpigmented lesional café-au-lait skin. From the magnitude of gene effects, we found that gene expression was affected most strongly by genotype and less so by lesional type. A total of 137 genes had a significant twofold or more up- (72) or downregulated (65) expression in NF1+/- melanocytes compared with NF1+/+ melanocytes. Melanocytes cultured from hyperpigmented café-au-lait skin showed 37 upregulated genes whereas only 14 were downregulated compared with normal skin melanocytes. In addition, significant genotype xlesional type interactions were observed for 465 genes. Differentially expressed genes were mainly involved in regulating cell proliferation and cell adhesion. A high number of transcription factor genes, among which a specific subset important in melanocyte lineage development, were downregulated in the cis-regulatory network governing the activation of the melanocyte-specific dopachrome tautomerase (DCT) gene. Although the results presented have been obtained with a restricted number of patients (one NF1 patient and one control) and using cDNA microarrays that may limit their interpretation, the data nevertheless addresses for the first time the effect of a heterozygous NF1 gene on the expression of the human melanocyte transcriptome and has generated several interesting candidate genes helpful in elucidating the etiopathology of café-au-lait macules in NF1 patients.