Neurofibromatosis type 1

At a glance

• Autosomal dominant, about 1 in 2,500 to 3,000 births, half of them de novo. Penetrance is complete, but expressivity varies widely, even within a family.
• Diagnosis is clinical, using the revised 2021 criteria (Legius, Genet Med), now including genetic testing and choroidal abnormalities.
• The tumour risks drive adult care: plexiform neurofibroma, MPNST, early breast cancer, phaeochromocytoma, GIST and glioma. Life expectancy is about 10 to 15 years shorter than average, mostly from cancer.