NF1 and plexiform neurofibroma: A study of 21 unrelated NF1 probands and 26 affected relatives shows that individuals with a 3-bp loss of a single amino-acid deletion at codon 992 (p.Met992del), 0.9% frequency in NF1 mutation individuals, present a mild clinical phenotype with CALMs and absence of neurofibroma manifestations (18, 19).