Presentación de un caso de enfermedad de Von Recklinghausen / Von Recklinghausen´s Disease: a Case Report

La neurofibromatosis 1 es una enfermedad genética, de herencia autosómica dominante, de alta penetrancia y expresividad muy variable. Se realizó una presentación de caso, seleccionando a un adulto de 27 años, de la raza negra, de procedencia haitiana, que desde niño presentaba verrugas diseminadas en todo el cuerpo y en esta ocasión fue admitido en el Hospital L Providence, pues tenía un neurofibroma de gran tamaño que le imposibilitaba el decúbito supino, apenas dormía por las molestias que le ocasionaba y además en el orden estético le producía algunas dificultades. Se indicó tratamiento quirúrgico al neurofibroma gigante que presentaba. Constituyeron las lesiones óseas, las manchas café con leche, el retraso pondoestatural y el retardo mental ligero, las características clínicas más frecuentes vistas. Se concluye entonces planteando que la neurofibromatosis tipo 1 es una enfermedad que afecta esencialmente el crecimiento celular del tejido neural, su curso es progresivo a lo largo de la vida, el diagnóstico es eminentemente clínico, donde las lesiones cutáneas constituyen el elemento característico...(AU)

The neurofibromatosis 1 is a genetic illness, of dominant autosomal heredity, high penetrance and very variable. A study was carried out, with a 27- year-old adult, black race, from Haiti .The patient had disseminated warts in the whole body since his childhood and he was admitted at L' Providence Hospital due to a neurofibroma of a great size that disabled him the supine,dorsal decubitus position, he hardly slept due to the difficulties that it caused him, even in the aesthetic order . Surgical treatment was indicated . The most frequent clinical characteristics were the bone lesions, café au lait spot, weight-height retardation and the slight mental retardation. The neurofibromatosis type 1 is a progressive illness that affects essentially the cellular growth of the neural tissue, the diagnosis is eminently clinical, where the cutaneous lesions constitute the characteristic element...(AU)

[From gene to disease; neurofibromatosis type 1]. / Van gen naar ziekte; neurofibromatosis type 1.

Neurofibromatosis type 1 (NF1) is an autosomal dominant disease characterised by café-au-lait spots, freckling in the axillary or inguinal region, dermal and plexiform neurofibromas and Lisch nodules. Complications are severe in one third of patients, and the clinical variability is pronounced, even within families. The NF1 gene has been localised to chromosome 17q11.2 and encodes the protein neurofibromin. The gene is proposed to be a tumour suppressor gene. Inactivation of neurofibromin leads to a disruption in cell growth regulation. Mutation analysis is possible but laborious, and therefore NF1 is generally a clinical diagnosis based on diagnostic criteria.

Lack of association of the (AAAT)6 allele of the GXAlu tetranucleotide repeat in intron 27b of the NF1 gene with autism.

A novel allele of the GXAlu tetranucleotide repeat in intron 27b of the neurofibromatosis 1 (NF1) gene has recently been reported to be present in 4.7% of autistic patients but not in controls. We have found the novel GXAlu allele absent in 204 patients from the South Carolina Autism Project and 200 controls. The autism population studied includes a significant number of patients with hypotonia, stereotyped behaviors, or postural, gait, and motor abnormalities similar to those seen in the patients previously reported to possess the novel GXAlu allele. This suggests that the novel (AAAT)6 GXAlu allele is not associated with autism.

Molecular characterization and gene content of breakpoint boundaries in patients with neurofibromatosis type 1 with 17q11.2 microdeletions.

Homologous recombination between poorly characterized regions flanking the NF1 locus causes the constitutional loss of approximately 1.5 Mb from 17q11.2 covering > or =11 genes in 5%-20% of patients with neurofibromatosis type 1 (NF1). To elucidate the extent of microheterogeneity at the deletion boundaries, we used single-copy DNA fragments from the extreme ends of the deleted segment to perform FISH on metaphase chromosomes from eight patients with NF1 who had large deletions. In six patients, these probes were deleted, suggesting that breakage and fusions occurred within the adjacent highly homologous sequences. Reexamination of the deleted region revealed two novel functional genes FLJ12735 (AK022797) and KIAA0653-related (WI-12393 and AJ314647), the latter of which is located closest to the distal boundary and is partially duplicated. We defined the complete reading frames for these genes and two expressed-sequence tag (EST) clusters that were reported elsewhere and are associated with the markers SHGC-2390 and WI-9521. Hybrid cell lines carrying only the deleted chromosome 17 were generated from two patients and used to identify the fusion sequences by junction-specific PCRs. The proximal breakpoints were found between positions 125279 and 125479 in one patient and within 4 kb of position 143000 on BAC R-271K11 (AC005562) in three patients, and the distal breakpoints were found at the precise homologous position on R-640N20 (AC023278). The interstitial 17q11.2 microdeletion arises from unequal crossover between two highly homologous WI-12393-derived 60-kb duplicons separated by approximately 1.5 Mb. Since patients with the NF1 large-deletion syndrome have a significantly increased risk of neurofibroma development and mental retardation, hemizygosity for genes from the deleted region around the neurofibromin locus (CYTOR4, FLJ12735, FLJ22729, HSA272195 (centaurin-alpha2), NF1, OMGP, EVI2A, EVI2B, WI-9521, HSA272196, HCA66, KIAA0160, and WI-12393) may contribute to the severe phenotype of these patients.

Quantification of splice variants using real-time PCR.

A reliable and robust method for measuring the expression of alternatively spliced transcripts is an important step in investigating the significance of each variant. So far, accurate quantification of splice variants has been laborious and difficult due to the intrinsic limitations of conventional methods. The many advantages of real-time PCR have made this technique attractive to study its application in quantification of splice isoforms. We use skipping of exon 37 in the NF1 gene as a model to compare and evaluate the different strategies for quantitating splice variants using real-time PCR. An overview of three different possibilities for detecting alternative transcripts is given. We propose the use of a boundary-spanning primer to quantify isoforms that differ greatly in abundance. We describe here a novel method for creating a reliable standard curve using one plasmid containing both alternative transcripts. In addition, we validate the use of an absolute standard curve based on a dilution series of fluorometrically quantified PCR products.

NF1 deletions in S-100 protein-positive and negative cells of sporadic and neurofibromatosis 1 (NF1)-associated plexiform neurofibromas and malignant peripheral nerve sheath tumors.

Although plexiform neurofibroma (PN) is thought to represent a benign neoplasm with the potential for malignant transformation (malignant peripheral nerve sheath tumor; MPNST), its neoplastic nature has been difficult to prove due to cellular heterogeneity, which hampers standard molecular genetic analysis. Its mixed composition typically includes Schwann cells, fibroblasts, perineurial-like cells, and mast cells. Although NF1 loss of heterozygosity has been reported in subsets of PNs, it remains uncertain which cell type(s) harbor these alterations. Using a dual-color fluorescence in situ hybridization and immunohistochemistry technique, we studied NF1 gene status in S-100 protein-positive and -negative cell subpopulations in archival paraffin-embedded specimens from seven PNs, two atypical PNs, one cellular/atypical PN, and eight MPNSTs derived from 13 patients, seven of which had neurofibromatosis type 1 (NF1). NF1 loss was detected in four of seven PNs and one atypical PN, with deletions entirely restricted to S-100 protein-immunoreactive Schwann cells. In contrast, all eight MPNSTs harbored NF1 deletions, regardless of S-100 protein expression or NF1 clinical status. Our results suggest that the Schwann cell is the primary neoplastic component in PNs and that S-100 protein-negative cells in MPNST represent dedifferentiated Schwann cells, which harbor NF1 deletions in both NF1-associated and sporadic tumors.

Mitotic recombination effects homozygosity for NF1 germline mutations in neurofibromas.

Pure populations of neurofibroma-derived Schwann cells bearing both NF1 mutated alleles (NF1-/-) have been isolated from different neurofibromas showing loss of heterozygosity of nearly the entire 17q chromosome. By comparing molecular and fluorescent in situ hybridization analysis of these cells, we demonstrate mitotic recombination is the mechanism underlying this type of loss of heterozygosity leading to reduction to homozygosity of NF1 germline mutation.

Biallelic inactivation of TP53 rarely contributes to the development of malignant peripheral nerve sheath tumors.

About 10% of the patients with neurofibromatosis type 1 (NF1) develop malignant peripheral nerve sheath tumors (MPNSTs), accounting for half of all MPNST cases. Several nonrandom chromosomal aberrations have been found, but the target genes remain mostly unrecognized. Mutations in the NF1 and TP53 genes have been found in some MPNSTs, and recent data from mouse models support a synergistic effect of these two genes in the development of MPNST. In the present study, we have analyzed 16 MPNSTs, including 11 from patients with NF1 and 5 sporadic cases, for mutations in the coding sequence of the TP53 gene (exons 2-11). We applied denaturing gradient gel electrophoresis and modifications of this technique for analyses of 12 genomic fragments, followed by direct sequencing for identification of the mutated base(s). None of the MPNSTs revealed mutations. The detection of control mutants for each fragment analyzed, the high sensitivity of the technique, the detection of polymorphisms in some samples, and the high content of tumor tissue in the biopsies imply that false negatives are highly unlikely. Although we cannot exclude that deletions including large parts of the gene remain undetected by the mutation analyses, previous comparative genomic hybridization (CGH), cytogenetic banding analysis, and/or loss of heterozygosity studies on 14 of the cases included here had revealed 17p deletions in only three. We thus conclude that TP53 biallelic inactivation is rare in MPNST, and that the potential impact of an altered TP53 pathway on the malignant transformation of a neurofibroma into an MPNST may more frequently occur by changes in other components of that pathway.

The Genoa experience of prenatal diagnosis in NF1.

Type 1 neurofibromatosis (NF1) is an autosomal dominant disorder with an incidence of about 1 in 3500 live births. Symptoms are highly variable from a few cafè-au-lait spots and axillary freckling to plexiform neurofibromas, optic gliomas, pseudarthrosis, and malignancy. Since disease causing mutations are dispersed throughout the gene, prenatal diagnosis is usually performed in familial cases by linkage analysis and rarely by direct characterization of the mutation. We have characterized 48 families and have performed four prenatal diagnoses. In three cases, the linkage analysis was carried out using informative markers. A direct approach using the protein truncation test (PTT) and sequencing was performed in one case in which a R1947X mutation was identified. The extreme variability of the phenotypic expression of the NF1 gene makes reproductive decisions in NF1 families very difficult, as molecular diagnosis cannot predict clinical expression of the disease. The psychological management of the couple is therefore difficult. In two of the three examined families the reproductive choices were not influenced by the specific manifestations of the disease in that family.

Hypermethylation of the neurofibromatosis type 1 (NF1) gene promoter is not a common event in the inactivation of the NF1 gene in NF1-specific tumours.

Neurofibromatosis type 1 (NFI) is a common autosomal dominant disorder characterised by café-au-lait spots, neurofibromas and iris hamartomas. Since the NF1 gene product neurofibromin contains a GAP-related domain involved in the down-regulation of p21(ras) oncogene activity, the NF1 gene has come to be regarded as a tumour-suppressor gene. One common mechanism of tumour-suppressor gene inactivation during tumorigenesis is promoter hypermethylation, this "epi-mutation" being functionally equivalent to a second-hit somatic mutation. To assess the importance of promoter hypermethylation in NF1 gene inactivation in NF1-related tumours, the methylation status of the NF1 promoter region was determined by bisulphite-modified genomic sequencing in NF1-specific tumours and peripheral blood lymphocytes (PBL) from both NF1 patients and normal controls. Tumour-specific CpG methylation of six distinct CpG sites was identified at positions -609, -429, 406, -383, -331 and -315 relative to the transcriptional start site. However, since all other CpG sites were unmethylated in all tissues examined, it is unlikely that CpG hypermethylation within the NF1 promoter represents a common mutational mechanism leading to neurofibroma formation.

Nf1;Trp53 mutant mice develop glioblastoma with evidence of strain-specific effects.

Astrocytomas are the leading cause of brain cancer in humans. Because these tumours are highly infiltrative, current treatments that rely on targeting the tumour mass are often ineffective. A mouse model for astrocytoma would be a powerful tool for dissecting tumour progression and testing therapeutics. Mouse models of astrocytoma have been designed to express oncogenic proteins in astrocytes, but have had limited success due to low tumour penetrance or limited tumour progression. We present here a mouse model of astrocytomas involving mutation of two tumour-suppressor genes, Nf1 and Trp53. Humans with mutations in NF1 develop neurofibromatosis type I (NF1) and have increased risk of optic gliomas, astrocytomas and glioblastomas. The TP53 tumour suppressor is often mutated in a subset of astrocytomas that develop at a young age and progress slowly to glioblastoma (termed secondary glioblastomas, in contrast to primary glioblastomas that develop rapidly de novo). This mouse model shows a range of astrocytoma stages, from low-grade astrocytoma to glioblastoma multiforme, and may accurately model human secondary glioblastoma involving TP53 loss. This is the first reported mouse model of astrocytoma initiated by loss of tumour suppressors, rather than overexpression of transgenic oncogenes.

Multiple coronary artery aneurysms in a child with neurofibromatosis type 1.

UNLABELLED: A number of frequently unrecognised vascular manifestations have been described in patients with neurofibromatosis type 1 (NF1), including involvement of the great vessels, cerebral, visceral and renal arteries. Rarely, changes in the coronary arteries have been reported in adults with NF1. We report on a 16-year-old boy affected by NF1 with dysmorphic features and three aneurysms in the mid-portion of the left descending coronary artery disclosed by chance during investigation for a malignant peripheral nerve sheath tumour. Molecular analysis detected a gross de novo deletion in the NF1 gene. The boy had had no previous cardiac symptoms but died suddenly after developing signs and symptoms suggestive of myocardial infarction. CONCLUSION: To the best of our knowledge, this represents the first report of multiple lesions in the coronary arteries in a child affected by neurofibromatosis type 1 with a known deletion of the neurofibromatosis type 1 gene.

Chromosome 17 loss-of-heterozygosity studies in benign and malignant tumors in neurofibromatosis type 1.

Neurofibromatosis type 1 (NF1) is a common autosomal dominant condition characterized by benign tumor (neurofibroma) growth and increased risk of malignancy. Dermal neurofibromas, arising from superficial nerves, are primarily of cosmetic significance, whereas plexiform neurofibromas, typically larger and associated with deeply placed nerves, extend into contiguous tissues and may cause serious functional impairment. Malignant peripheral nerve sheath tumors (MPNSTs) seem to arise from plexiform neurofibromas. The NF1 gene, on chromosome segment 17q11.2, encodes a protein that has tumor suppressor function. Loss of heterozygosity (LOH) for NF1 has been reported in some neurofibromas and NF1 malignancies, but plexiform tumors have been poorly represented. Also, the studies did not always employ the same markers, preventing simple comparison of the frequency and extent of LOH among different tumor types. Our chromosome 17 LOH analysis in a cohort of three tumor types was positive for NF1 allele loss in 2/15 (13%) dermal neurofibromas, 4/10 (40%) plexiform neurofibromas, and 3/5 (60%) MPNSTs. Although the region of loss varied, the p arm (including TP53) was lost only in malignant tumors. The losses in the plexiform tumors all included sequences distal to NF1. No subtle TP53 mutations were found in any tumors. This study also reports the identification of both NF1 "hits" in plexiform tumors, further supporting the tumor suppressor role of the NF1 gene in this tumor type.

Exhaustive mutation analysis of the NF1 gene allows identification of 95% of mutations and reveals a high frequency of unusual splicing defects.

Neurofibromatosis type 1 (NF1) is one of the most common autosomal dominant disorders and is caused by mutations in the NF1 gene. Mutation detection is complex due to the large size of the NF1 gene, the presence of pseudogenes and the great variety of possible lesions. Although there is no evidence for locus heterogeneity in NF1, mutation detection rates rarely exceed 50%. We studied 67 unrelated NF1 patients fulfilling the NIH diagnostic criteria, 29 familial and 38 sporadic cases, using a cascade of complementary techniques. We performed a protein truncation test starting from puromycin-treated EBV cell lines and, if no mutation was found, continued with heteroduplex, FISH, Southern blot and cytogenetic analysis. We identified the germline mutation in 64 of 67 patients and 32 of the mutations are novel. This is the highest mutation detection rate reported in a study of typical NF1 patients. All mutations were studied at the genomic and RNA level. The mutational spectrum consisted of 25 nonsense, 12 frameshift, 19 splice mutations, six missense and/or small in-frame deletions, one deletion of the entire NF1 gene, and a translocation t(14;17)(q32;q11.2). Our data suggest that exons 10a-10c and 37 are mutation-rich regions and that together with some recurrent mutations they may account for almost 30% of the mutations in classical NF1 patients. We found a high frequency of unusual splice mutations outside of the AG/GT 5 cent and 3 cent splice sites. As some of these mutations form stable transcripts, it remains possible that a truncated neurofibromin is formed.

Genetic and cellular defects contributing to benign tumor formation in neurofibromatosis type 1.

Neurofibromatosis type 1 (NF1) is a common inherited cancer predisposition syndrome. The NF1 gene product, neurofibromin, is hypothesized to function as a tumor suppressor and nearly all NF1 patients develop benign peripheral nerve tumors. These neurofibromas presumably arise from NF1 inactivation in S100(+)Schwann cells, but there is no formal proof for this mechanism. We demonstrate that fibro-blasts isolated from neurofibromas carried at least one normal NF1 allele and expressed both NF1 mRNA and protein, whereas the S100(+)cells typically lacked the NF1 transcript. Our findings further indicate that additional molecular events aside from NF1 inactivation in Schwann cells and/or other neural crest derivatives contribute to neurofibroma formation.

Molecular analysis of the 5'-flanking region of the neurofibromatosis type 1 (NF1) gene: identification of five sequence variants.

Dideoxy fingerprinting was used to analyse the 5' flanking region of the neurofibromin (NF1) gene in a panel of 380 neurofibromatosis type 1 (NF1) patients. Five polymorphisms/rare variants were identified at positions -412, - 402, + 16, + 25 and + 132, but control data indicated that these were unlikely to be of pathological significance. Promoter mutations in the NF1 gene are not, therefore, a common cause of NF1. This notwithstanding, a reporter gene assay was performed to determine if these variants could affect the expression of the NF1 gene, and all three changes in the 5'-untranslated region (UTR) (+ 16, + 25, + 132) were found to be associated with a 60-70% increase in reporter gene expression.