We recently provided an update on mosaicism in neurofibromatosis 2 (NF2).1 This showed that the chances of a de novo patient with NF2 being mosaic for the underlying predisposing mutation increased with age at presentation with vestibular schwannoma (VS) and was particularly high in patients with unilateral presentation of VS, but who still had at least two further NF2 related tumours in order to fulfil Manchester criteria.2 3 While our paper addressed the mosaic risk there was not a breakdown of this risk by age at VS diagnosis. We have now analysed this in four age cohorts to derive figures for mosaicism and offspring risk both before and after lymphocyte DNA testing with sequencing and multiple ligation dependant …