US Selumetinib Registry

Inclusion Criteria: * Participants diagnosed with NF1 and PN * Started selumetinib between the ages of 2 to 18 years inclusive, and initiated selumetinib treatment on or after 10 April 2020, including patients who: * Discontinued selumetinib before enrollment; or * Initiated treatment before enrollment and are currently on selumetinib; or * Initiated selumetinib on the day of enrollment or intend to initiate selumetinib within 3 months after enrollment * Able to give written informed consent. Participant or participant's parent/legal guardian must be willing and able to give written informed consent and the participant (if minor) must be willing to give written informed assent. Exclusion Criteria: * Participants currently participating in any clinical trials at time of enrollment or initiation of selumetinib.