Table 4 Frequency and age of onset of major clinical manifestations of neurofibromatosis 1.
| Clinical manifestation | Frequency (%) | Age of onset |
|---|---|---|
| Café au lait patches | >99 | Birth to 12 y |
| Skin‐fold freckling | 85 | 3 y to adolescence |
| Lisch nodules | 90–95 | >3 y |
| Cutaneous neurofibromas | >99 | >7 y (usually late adolescence) |
| Plexiform neurofibromas | 30 (visible) –50 (on imaging) | Birth to 18 y |
| Disfiguring facial plexiform neurofibromas | 3–5 | Birth to 5 y |
| Malignant peripheral nerve sheath tumour | 2–5 (8–13% lifetime risk) | 5–75 y |
| Scoliosis | 10 | Birth to 18 y |
| Scoliosis requiring surgery | 5 | Birth to 18 y |
| Pseudarthrosis of tibia | 2 | Birth to 3 y |
| Renal artery stenosis | 2 | Lifelong |
| Phaeochromocytoma | 2 | >10 y |
| Severe cognitive impairment (IQ <70) | 4–8 | Birth |
| Learning problems | 30–60 | Birth |
| Epilepsy | 6–7 | Lifelong |
| Optic pathway glioma | 15 (only 5% symptomatic) | Birth to 7 y (up to 30 y) |
| Cerebral gliomas | 2–3 | Lifelong |
| Sphenoid wing dysplasia | <1 | Congenital |
| Aqueduct stenosis | 1.5 | Lifelong |