Two case reports describe trametinib treatment for non-ossifying fibromas driven by mosaic KRAS variants

A case series published in Communications Medicine (Springer Nature) reports on two patients with multiple non-ossifying fibromas — benign but potentially problematic bone lesions — in whom somatic mosaic mutations in KRAS were identified as the likely driver. Both patients were treated with trametinib, a MEK inhibitor approved for use in KRAS-driven malignancies.

Non-ossifying fibromas are typically solitary incidental lesions, but multiple lesions can be associated with café-au-lait macules and other features; the underlying molecular basis has not always been clear. The identification of activating KRAS mosaic variants provides a mechanistic rationale for the use of RAS-MAPK pathway inhibition in this setting.

Case reports by their nature provide limited generalisability, and this publication does not constitute evidence that trametinib is an established treatment for non-ossifying fibromas. The authors present the cases as illustrative of the potential relevance of somatic mosaicism screening and targeted pathway inhibition in rare skeletal conditions. The specific institutions and authorship are not available from the feed entry; readers should consult the full article in Communications Medicine.

This report is of interest to researchers and clinicians working in somatic mosaicism, RAS-opathies, and rare skeletal disease, and may be informative for genetic counsellors advising families affected by related conditions.