Reassessment of the NF1 Variants of Unknown Significance Found During the 20-Year Activity of a Genetics Diagnostic Laboratory

Martorana, Davide; Barili, Valeria; Uliana, Vera; Ambrosini, Enrico; Riva, Mattéo; Sensi, Erika De; Luppi, Elena; Messina, Corinne; Caleffi, Edoardo; Pisani, Francesco

doi:10.2139/ssrn.4252931

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“…A recent study performed in a diagnostic laboratory in Italy, where a 20 years reassessment of NF1 VUSs, 85 out of 589 (14%) NF1 tests requested. Of these VUSs 66% of missense VUSs were reclassified to likely pathogenic/pathogenic (Martorana et al, 2023). It is likely that the VUS identified in the current study will be reassessed in the future when more functional evidence is available.…”

Section: Discussionmentioning

confidence: 89%

Mutation analysis and clinical profile of South African patients with Neurofibromatosis type 1 (NF1) phenotype

Mudau,

Dillon,

Smal

et al. 2024

Front. Genet.

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Neurofibromatosis type 1 (NF1) is an autosomal dominant genetic condition with complete age-dependent penetrance, variable expressivity and a global prevalence of ∼1/3,000. It is characteriszed by numerous café-au-lait macules, skin freckling in the inguinal or axillary regions, Lisch nodules of the iris, optic gliomas, neurofibromas, and tumour predisposition. The diagnostic testing strategy for NF1 includes testing for DNA single nucleotide variants (SNVs), copy number variants (CNVs) as well as RNA analysis for deep intronic and splice variants, which can cumulatively identify the causative variant in 95% of patients. In the present study, NF1 patients were screened using a next-generation sequencing (NGS) assay targeting NF1 exons and intron/exon boundaries for SNV and NF1 multiple ligation-dependent probe amplification (MLPA) analysis for CNV detection. Twenty-six unrelated Southern African patients clinically suspected of having NF1, based on the clinical diagnostic criteria developed by the National Institute of Health (NIH), were included in the current study. A detection rate of 58% (15/26) was obtained, with SNVs identified in 80% (12/15) using a targeted gene panel and NF1 gene deletion in 20% (3/15) identified using MLPA. Ten patients (38%) had no variants identified, although they met NF1 diagnostic criteria. One VUS was identified in this study in a patient that met NF1 diagnostic criteria, however there was no sufficient information to classify variant as pathogenic. The clinical features of Southern African patients with NF1 are similar to that of the known NF1 phenotype, with the exception of a lower frequency of plexiform neurofibromas and a higher frequency of developmental/intellectual disability compared to other cohorts. This is the first clinical and molecular characterisation of a Southern African ancestry NF1 cohort using both next-generation sequencing and MLPA analysis. A significant number of patients remained without a diagnosis following DNA-level testing. The current study offers a potential molecular testing strategy for our low resource environment that could benefit a significant proportion of patients who previously only received a clinical diagnosis without molecular confirmation.

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Section: Discussionmentioning

confidence: 89%