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  • Neurofibromatosis type 1 families with first-degree relatives harbouring distinct NF1 pathogenic variants. Genetic counselling and familial diagnosis: what should be offered?

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Diagnostics
Original research
Neurofibromatosis type 1 families with first-degree relatives harbouring distinct NF1 pathogenic variants. Genetic counselling and familial diagnosis: what should be offered?
  1. Belen Garcia1,2,
  2. Nuria Catasus2,
  3. Andrea Ros1,2,
  4. Inma Rosas2,3,
  5. Alejandro Negro2,3,
  6. Mercedes Guerrero-Murillo2,3,
  7. Ana Maria Valero4,
  8. Anna Duat-Rodriguez5,
  9. Juan Luis Becerra6,
  10. Sandra Bonache2,3,
  11. Conxi Lázaro Garcia7,8,
  12. Carmina Comas9,
  13. Isabel Bielsa10,
  14. Eduard Serra8,11,
  15. Concepción Hernández-Chico12,13,
  16. Yolanda Martin12,13,
  17. Elisabeth Castellanos2,3,
  18. Ignacio Blanco1,2
  1. 1 Genetic Counseling Unit, Clinical Genetics Service, Northern Metropolitan Clinical Laboratory, Hospital Universitari Germans Trias i Pujol, Badalona, Spain
  2. 2 Clinical Genomics Research Unit, Foundation Institute of Research in Health Sciences Germans Trias i Pujol, Badalona, Spain
  3. 3 Clinical Genomics Unit—Genetics Service, Hospital Universitari Germans Trias i Pujol, Badalona, Spain
  4. 4 Servicio de Genética, Hospital Universitario Ramon y Cajal, Madrid, Spain
  5. 5 Neurology Service, Hospital Infantil Universitario Niño Jesús, Madrid, Spain
  6. 6 Neurology, Hospital Universitari Germans Trias i Pujol, Badalona, Spain
  7. 7 Hereditary Cancer Program, Program in Molecular Mechanisms and Experimental Therapy in Oncology (Oncobell), IDIBELL, Catalan Institute of Oncology, L'Hospitalet de Llobregat, Spain
  8. 8 Centro de Investigación Biomédica en Red de Cáncer, CIBERONC, Madrid, Spain
  9. 9 Department of Obstetrics, Hospital Universitari Germans Trias i Pujol, Badalona, Spain
  10. 10 Dermatology, Hospital Universitari Germans Trias i Pujol, Badalona, Spain
  11. 11 Hereditary Cancer Group, Fundació Institut d'Investigació en Ciències de la Salut Germans Trias i Pujol, Badalona, Spain
  12. 12 Servicio de Genética, IRYCIS, Hospital Universitario Ramon y Cajal, Madrid, Spain
  13. 13 Centro de Investigación Biomédica en Red de Enfermedades Raras, CIBERER, Valencia, Spain
  1. Correspondence to Dr Elisabeth Castellanos, Clinical Genomics Unit - Genetics Service, Hospital Universitari Germans Trias i Pujol, Badalona, Barcelona, Spain; ecastellanos{at}igtp.cat

Abstract

Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder caused by pathogenic variants in NF1. Recently, NF1 testing has been included as a clinical criterion for NF1 diagnosis. Additionally, preconception genetic counselling in patients with NF1 focuses on a 50% risk of transmitting the familial variant as the risk of having a sporadic NF1 is considered the same as the general population.

Methods 829 individuals, 583 NF1 sporadic cases and 246 patients with NF1 with documented family history, underwent genetic testing for NF1. Genotyping and segregation analysis of NF1 familial variants was determined by microsatellite analysis and NF1 sequencing.

Results The mutational analysis of NF1 in 154 families with two or more affected cases studied showed the co-occurrence of two different NF1 germline pathogenic variants in four families. The estimated mutation rate in those families was 3.89×10–3, 20 times higher than the NF1 mutation rate (~2×10−4) (p=0.0008). Furthermore, the co-occurrence of two different NF1 germline pathogenic variants in these families was 1:39, 60 times the frequency of sporadic NF1 (1:2500) (p=0.003). In all cases, the de novo NF1 pathogenic variant was present in a descendant of an affected male. In two cases, variants were detected in the inherited paternal wild-type allele.

Conclusions Our results, together with previous cases reported, suggest that the offspring of male patients with NF1 could have an increased risk of experiencing de novo NF1 pathogenic variants. This observation, if confirmed in additional cohorts, could have relevant implications for NF1 genetic counselling, family planning and NF1 genetic testing.

  • human genetics
  • genetic counseling
  • genetic testing

Data availability statement

All data relevant to the study are included in the article or uploaded as supplementary information.

https://doi.org/10.1136/jmedgenet-2021-108301

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    Data availability statement

    All data relevant to the study are included in the article or uploaded as supplementary information.

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    Footnotes

    • BG and NC are joint first authors.

    • Twitter @-, @elishabeba82

    • BG and NC contributed equally.

    • EC and IB contributed equally.

    • Correction notice The articles has been corrected since it was published Online First. The funding statement has been amended.

    • Contributors EC and IB designed the study and wrote the manuscript that was revised, corrected and improved by all authors. Both, EC and IB are the guarantors of this work. BG, NC and YM performed most of the experimental work and analysed the data. MG-M performed statistical analysis. IR, AN and AV performed genetic analysis. AR, AD, JLB, CC and IB contributed with clinical data collection. SB, CH-C, CLG and ES provided scientific input. NC generated the figures for the paper and contributed in writing the manuscript. All authors approved the final version of the manuscript.

    • Funding This work has been funded by Instituto de Salud Carlos III through the project " PI20/00215” and co-funded by European Union (ERDF, "A way to make Europe"), The Children’s Tumor Foundation (CTF-2019-05-005), the Spanish Association of NF Affected (AANF), Fundación Proyecto Neurofibromatosis, the Catalan NF Association (AcNeFi); Fundació La Marató de TV3 (126/C /C/2020) and the Generalitat of Catalonia (2017 SGR 496).

    • Competing interests None declared.

    • Provenance and peer review Not commissioned; externally peer reviewed.

    • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.