Neurofibromatosis

What it is

Neurofibromatosis type 1, also known as von Recklinghausen disease, is autosomal dominant, but 50% are the result of new mutations. The incidence is 1:3,000 and the mutation is in the NF1 gene on 17q11.2, which codes for the neurofibromin protein; the NF1 gene sits on chromosome 17.

Neurofibromatosis type 2 is also autosomal dominant, with the NF2 gene on chromosome 22. Both are neurocutaneous syndromes, and in NF2 the signs are bilateral.

How it presents

The skin and eye signs of type 1, with what each one is:

• Café-au-lait spots: hypermelanotic macules, hyperpigmented lesions that vary in color from light brown to dark brown, with borders that may be smooth or irregular.
• Lisch nodules: circumscribed melanotic iris, that is hamartomas of the iris.
• Freckles: small round hyperpigmented spots in axilla or inguinal area.
• Neurofibroma: multiple subcutaneous papules and macules.

Beside these there is bone involvement, for example scoliosis and bone dysplasia, and features of melanocyte dysfunction. Learning disorders, abnormal speech development, and seizures are common.

In type 2 the skin changes are café au lait spots as well, but nonspecific there.