CHAPTER 70

Neurofibromatosis 1

Introduction/Etiology/Epidemiology

• Formerly called von Recklinghausen disease, neurofibromatosis 1 (NF1) is an autosomal-dominant neurocutaneous disorder that occurs in persons of all races and ethnicities.

• Incidence is approximately 1 per 3,000 births

• Penetrance is 100%; expressivity is variable.

• New mutations account for 25% to 50% of cases.

• NF1 is caused by mutation in the tumor-suppressor gene on the long arm of chromosome 17.

• Loss of heterozygosity at the NF1 tumor locus leads to increased tumorigenesis.

Signs and Symptoms

• Café au lait spots and intertriginous freckling

— Flat, pigmented macules frequently present at birth (Figure 70-1)

— Increase in number during the first 3 to 5 years after birth

— Café au lait spots are nonspecific to NF1 (Box 70-1)

— Greater than 95% of children with NF1 will have more than 6 café au lait spots by 6 years of age.

• Neurofibromas

— Benign nerve sheath tumors consisting of Schwann cells, fibroblasts, and perineural cells.

— Cutaneous neurofibromas protrude just above the skin surface or lie just under the skin with an overlying violaceous hue.

Figure 70-1. Café au lait spots in a Black infant with neurofibromatosis 1.

From Tekin M, Bodurtha JN, Riccardi VM. Café au lait spots: the pediatrician’s perspective. Pediatr Rev. 2001;22:82–90.

Box 70-1. Syndromes With Café Au Lait Spots

Figure 70-2. Plexiform neurofibroma with overlying hyperpigmentation and hypertri-chosis.

— Subcutaneous neurofibromas arise from peripheral nerves, lie deeper, and are generally hard and nodular.

— Generally begin to appear during the second decade after birth, following the onset of puberty

• Plexiform neurofibromas (Figure 70-2)

— Histologically similar to cutaneous neurofibromas that involve single or multiple nerve fascicles arising from branches of major nerves

— Often have overlying hyperpigmentation or hair

— Generally present at birth or become apparent in the first several years

— Unpredictable growth rate

— May cause pain and neurologic dysfunction from pressure and interdigitation into peripheral nerves (neuropathy)

— May lead to disfigurement or organ compromise (eg, blindness, obstructive uropathy)

— Have high risk of eventual malignant transformation

• Lisch nodules (Figure 70-3)

— Slightly raised, well-circumscribed melanocytic hamartomas of the iris best seen with a slit lamp.

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