Snapshot A 3-year-old boy presents to his pediatrician for multiple hyperpigmented lesions on his skin. Family history is significant for a genetic disorder in which his father to have similar skin lesions that are much larger. Medical history is otherwise unremarkable. On physical exam, there are 7 café au lait macules about 6 mm in size throughout the body along with axillary freckling. Introduction Definition an autosomal dominant disorder that can present with café au lait macules neurofibromas Lisch nodules axillary and inguinal freckling pheochromocytoma optic glioma Etiology Pathophysiology mutated NF1 gene insufficiently creates neurofibromin, a tumor suppressor this, in turn, dysregulates cell growth and development Genetics autosomal dominant mutation in NF1 gene on chromosome 17 complete penetrance but variable expression Presentation Physical exam café au lait macules typically by age 2 axillary or inguinal freckling typically by age 3-5 cutaneous neurofibromas Lisch nodules Studies Preventative prenatal testing Differential Neurofibromatosis type 2 differentiating factors mutation in NF2 gene on chromosome 22 findings include bilateral acoustic schwannomas juvenile cataracts meningiomas ependymomas DIAGNOSIS Making the diagnosis clinical diagnosis typically made in children genetic counseling Treatment Treatment is targeted to the clinical manifestations e.g., surgical removal with discrete neurofibromas Complications Increased risk of malignancy Prognosis Associated with increased mortality