High incidence of Noonan syndrome features including short stature and pulmonic stenosis in patients carrying NF1 missense mutations affecting p.Arg1809: genotype-phenotype correlation

Neurofibromatosis type 1 (NF1) is one of the most frequent genetic disorders, affecting 1:3,000 worldwide. Identification of genotype-phenotype correlations is challenging because of the wide range clinical variability, the progressive nature of the disorder, and extreme diversity of the mutational spectrum. We report 136 individuals with a distinct phenotype carrying one of five different NF1 missense mutations affecting p.Arg1809. Patients presented with multiple cafe-au-lait macules (CALM) with or without freckling and Lisch nodules, but no externally visible plexiform neurofibromas or clear cutaneous neurofibromas were found. About 25% of the individuals had Noonan-like features. Pulmonic stenosis and short stature were significantly more prevalent compared with classic cohorts (P<0.0001). Developmental delays and/or learning disabilities were reported in over 50% of patients. Melanocytes cultured from a CALM in a segmental NF1-patient showed two different somatic NF1 mutations, p.Arg1809Cys and a multi-exon deletion, providing genetic evidence that p.Arg1809Cys is a loss-of-function mutation in the melanocytes and causes a pigmentary phenotype. Constitutional missense mutations at p.Arg1809 affect 1.23% of unrelated NF1 probands in the UAB cohort, therefore this specific NF1 genotype-phenotype correlation will affect counseling and management of a significant number of patients

Expanding the clinical phenotype of individuals with a 3-bp in-frame deletion of the NF1 gene (c.2970_2972del): an update of genotype–phenotype correlation

Purpose: Neurofibromatosis type 1 (NF1) is characterized by a highly variable clinical presentation, but almost all NF1-affected adults present with cutaneous and/or subcutaneous neurofibromas. Exceptions are individuals heterozygous for the NF1 in-frame deletion, c.2970_2972del (p.Met992del), associated with a mild phenotype without any externally visible tumors. Methods: A total of 135 individuals from 103 unrelated families, all carrying the constitutional NF1 p.Met992del pathogenic variant and clinically assessed using the same standardized phenotypic checklist form, were included in this study. Results: None of the individuals had externally visible plexiform or histopathologically confirmed cutaneous or subcutaneous neurofibromas. We did not identify any complications, such as symptomatic optic pathway gliomas (OPGs) or symptomatic spinal neurofibromas; however, 4.8% of individuals had nonoptic brain tumors, mostly low-grade and asymptomatic, and 38.8% had cognitive impairment/learning disabilities. In an individual with the NF1 constitutional c.2970_2972del and three astrocytomas, we provided proof that all were NF1-associated tumors given loss of heterozygosity at three intragenic NF1 microsatellite markers and c.2970_297

A refined genetic map of the region of chromosome 17 surrounding the von recklinghausen neurofibromatosis (NF1) gene

The von Recklinghausen neurofibromatosis (NF1) gene has been mapped to the pericentromeric region of chromosome 17. We conducted linkage analyses of NF1 by using 10 polymorphic DNA markers from this chromosomal region. We ascertained 20 American Caucasian NF1 families (163 individuals, 98 NF1 affected) in Michigan and Ohio and also studied a large family ascertained primarily in North Carolina. The following markers were used in this study: HHH202, TH17.19, D17Z1, ERBA1, EW203, EW206, EW207, EW301, CRI-L581, and CRI-L946. NF1 did not recombine with either TH17.19 or HHH202 in any of the informative meioses surveyed (maximum lod scores of 17.04 and 7.21, respectively, at a recombination fraction of .00), indicating that these markers map very close to the NF1 gene. We also report evidence of three instances of recombination between NF1 and the centromeric marker D17Z1 (maximum lod score of 13.43 at a recombination fraction of .04), as well as two crossovers between pairs of marker loci. We find no evidence of locus heterogeneity, and our results support the localization of the NF1 gene to proximal chromosome 17q

Approaches to treating NF1 tibial pseudarthrosis: Consensus from the children\u27s tumor foundation NF1 bone abnormalities consortium

BACKGROUND: Neurofibromatosis 1 (NF1) is an autosomal dominant disorder with various skeletal abnormalities occurring as part of a complex phenotype. Tibial dysplasia, which typically presents as anterolateral bowing of the leg with subsequent fracture and nonunion (pseudarthrosis), is a serious but infrequent osseous manifestation of NF1. Over the past several years, results from clinical and experimental studies have advanced our knowledge of the role of NF1 in bone. On the basis of current knowledge, we propose a number of concepts to consider as a theoretical approach to the optimal management of tibial pseudarthrosis. METHODS: A literature review for both clinical treatment and preclinical models for tibial dysplasia in NF1 was performed. Concepts were discussed and developed by experts who participated in the Children\u27s Tumor Foundation sponsored International Bone Abnormalities Consortium meeting in 2011. RESULTS: Concepts for a theoretical approach to treating tibial pseudarthrosis include: bone fixation appropriate to achieve stability in any given case; debridement of the fibrous pseudarthrosis tissue between the bone segments associated with the pseudarthrosis; creating a healthy vascular bed for bone repair; promoting osteogenesis; controlling overactive bone resorption (catabolism); prevention of recurrence of the fibrous pseudarthrosis tissue ; and achievement of long-term bone health to prevent recurrence. CONCLUSIONS: Clinical trials are needed to assess effectiveness of the wide variation of surgical and pharmacologic approaches currently in practice for the treatment of tibial pseudarthrosis in NF1. LEVEL OF EVIDENCE: Level V, expert opinion. Copyright © 2013 by Lippincott Williams & Wilkins

Back to the future: Proceedings from the 2010 NF Conference How to Cite this Article: Huson SM, Acosta MT, Belzberg AJ, Bernards A, Chernoff J, Cichowski K, Gareth Evans D, Ferner RE, Giovannini M, Korf BR, Listernick R, North KN, Packer RJ, Parada LF, Peltonen J, Ramesh V, Reilly KM, Risner JW, Schorry EK, Uphadyaya M, Viskochil DH, Zhu Y, Hunter-Schaedle K, Giancotti FG. 2011. Back to the future: Proceedings from the 2010 NF Conference. Am J Med Genet Part A 155:307–321.

The neurofibromatoses (NF) encompass the rare diseases NF1, NF2, and schwannomatosis. The NFs affect 100,000 Americans; over 2 million persons worldwide; and are caused by mutation of tumor suppressor genes. Individuals with NF1 in particular may develop tumors anywhere in the nervous system; additional manifestations can include learning disabilities, bone dysplasia, cardiovascular defects, unmanageable pain, and physical disfigurement. Ultimately, the NFs can cause blindness, deafness, severe morbidity, and increased mortality and NF1 includes a risk of malignant cancer. Today there is no treatment for the NFs (other than symptomatic); however, research efforts to understand these genetic conditions have made tremendous strides in the past few years. Progress is being made on all fronts, from discovery studies—understanding the molecular signaling deficits that cause the manifestations of NF—to the growth of preclinical drug screening initiatives and the emergence of a number of clinical trials. An important element in fuelling this progress is the sharing of knowledge, and to this end, for over 20 years the Children's Tumor Foundation has convened an annual NF Conference, bringing together NF professionals to share ideas and build collaborations. The 2010 NF Conference held in Baltimore, MD June 5–8, 2010 hosted over 300 NF researchers and clinicians. This paper provides a synthesis of the highlights presented at the Conference and as such, is a “state-of-the-field” for NF research in 2010. © 2010 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/79423/1/33804_ftp.pd