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. 2020 Jan;22(1):53-59.
doi: 10.1038/s41436-019-0598-7. Epub 2019 Jul 5.

Incidence of mosaicism in 1055 de novo NF2 cases: much higher than previous estimates with high utility of next-generation sequencing

D Gareth Evans  1 , Claire L Hartley  2 , Philip T Smith  2 , Andrew T King  3 , Naomi L Bowers  2 , Simon Tobi  2 , Andrew J Wallace  2 , Mary Perry  2 , Raji Anup  2 , Simon K W Lloyd  4   5 , Scott A Rutherford  3 , Charlotte Hammerbeck-Ward  3 , Omar N Pathmanaban  3 , Emma Stapleton  4   5 , Simon R Freeman  4   5 , Mark Kellett  6 , Dorothy Halliday  7 , Allyson Parry  8 , Juliette J Gair  9 , Patrick Axon  9 , Roger Laitt  10 , Owen Thomas  10 , Shazia K Afridi  11 , Rupert Obholzer  11 ; English Specialist NF research group; Chris Duff  12 , Stavros M Stivaros  13 , Grace Vassallo  13 , Elaine F Harkness  14 , Miriam J Smith  2
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Free article

Incidence of mosaicism in 1055 de novo NF2 cases: much higher than previous estimates with high utility of next-generation sequencing

D Gareth Evans et al. Genet Med. 2020 Jan.
Free article

Abstract

Purpose: To evaluate the incidence of mosaicism in de novo neurofibromatosis 2 (NF2).

Methods: Patients fulfilling NF2 criteria, but with no known affected family member from a previous generation (n = 1055), were tested for NF2 variants in lymphocyte DNA and where available tumor DNA. The proportion of individuals with a proven or presumed mosaic NF2 variant was assessed and allele frequencies of identified variants evaluated using next-generation sequencing.

Results: The rate of proven/presumed mosaicism was 232/1055 (22.0%). However, nonmosaic heterozygous pathogenic variants were only identified in 387/1055 (36.7%). When variant detection rates in second generation nonmosaics were applied to de novo cases, we assessed the overall probable mosaicism rate to be 59.7%. This rate differed by age from 21.7% in those presenting with bilateral vestibular schwannoma <20 years to 80.7% in those aged ≥60 years. A mosaic variant was detected in all parents of affected children with a single-nucleotide pathogenic NF2 variant.

Conclusion: This study has identified a very high probable mosaicism rate in de novo NF2, probably making NF2 the condition with the highest expressed rate of mosaicism in de novo dominant disease that is nonlethal in heterozygote form. Risks to offspring are small and probably correlate with variant allele frequency detected in blood.

Keywords: LZTR1; NF2; mosaicism; neurofibromatosis type 2; schwannoma.

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References

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