A rare severe form of neurofibromatosis type 1 (NF1) characterized by mild facial dysmorphism, developmental delay, intellectual disability, increased risk of malignancies, and a large number of neurofibromas. The disease is MONDO_0013357 (chromosome 17q11.2 deletion syndrome, 1.4Mb). Also known as: 17q11 microdeletion syndrome, Del(17)(q11), MMFD, NF1 microdeletion syndrome, NF1 microduplication syndrome, RNF135-related overgrowth syndrome, Van Asperen syndrome, chromosome 17q11.2 deletion syndrome.