• Also called von Recklinghausen disease, NF1
• Defect in neurofibromin gene at 17q11.2; protein is widely expressed tumor suppressor gene that downregulates p21 ras oncoprotein; highest levels in neural tissue; gene has numerous sites of mutation; variable phenotypic expression
• 1/3000 individuals, 50% from autosomal dominant inheritance, 50% are new mutations
• Adrenomedullin (ADM) is serum biomarker of NF1 (Clin Cancer Res 2010;16:5048)

• Multiple neurofibromas (plexiform, solitary); plexiform are relatively specific
• 6 or more cafe au lait spots over nerve trunks, 1.5 cm or larger (cafe au lait spot: increase in melanin in epidermal basal layer, may overlie a neurofibroma, smooth delicate margins; solitary café au lait spots are normal)
• Lisch nodules (pigmented iris hamartomas, 94% by age 6)
• 2-4x increased risk of other tumors (childhood CML, ganglioneuroma, meningioma, pheochromocytoma, rhabdomyosarcoma); 5-13% develop MPNST; also acoustic neuroma (schwannoma), astrocytoma, gastric carcinoid, GIST, glomus tumor, lipoma, optic nerve glioma, Wilm tumor (Hum Genomics 2011;5:623)
• Nontumors: congenital malformations, fibrosing alveolitis, megacolon, skeletal lesions (30%-spinal deformities [kyphoscoliosis], bone cysts)

Lisch nodule

Cafe au lait spots

• Albright's syndrome: polyostotic fibrous dysplasia of bone, patchy dermal pigmentation, endocrine dysfunction

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