Table 4

 Frequency and age of onset of major clinical manifestations of neurofibromatosis 1

Clinical manifestationFrequency (%)Age of onset
Café au lait patches>99Birth to 12 y
Skin-fold freckling853 y to adolescence
Lisch nodules90–95>3 y
Cutaneous neurofibromas>99>7 y (usually late adolescence)
Plexiform neurofibromas30 (visible) –50 (on imaging)Birth to 18 y
Disfiguring facial plexiform neurofibromas3–5Birth to 5 y
Malignant peripheral nerve sheath tumour2–5 (8–13% lifetime risk)5–75 y
Scoliosis10Birth to 18 y
Scoliosis requiring surgery5Birth to 18 y
Pseudarthrosis of tibia2Birth to 3 y
Renal artery stenosis2Lifelong
Phaeochromocytoma2>10 y
Severe cognitive impairment (IQ <70)4–8Birth
Learning problems30–60Birth
Optic pathway glioma15 (only 5% symptomatic)Birth to 7 y (up to 30 y)
Cerebral gliomas2–3Lifelong
Sphenoid wing dysplasia<1Congenital
Aqueduct stenosis1.5Lifelong