Neurofibromatosis type 1 (NF1) is an autosomal dominant condition that stems from a pathogenic variant in the NF1 gene, which regulates the production of the tumor-suppressing neurofibromin protein. NF1 disorder is characterized by pigmentation changes (e.g., café au lait spots; see image), cutaneous neurofibromas, malignant nerve sheath tumors, gastrointestinal stromal tumors, and intellectual disorders. Signs and symptoms vary widely, but NF1 disorders occur in 1 in about 3,000–4,000 people. Almost half of the cases are de novo.