Neurofibromatosis type 1

What it is

Neurofibromatosis type 1, also known as von Recklinghausen disease, has an incidence of 1:3,000 and follows a mutation in the NF1 gene on 17q11.2, which codes for the neurofibromin protein. Among the neurocutaneous syndromes it is the autosomal dominant one with the NF1 gene on chromosome 17.

Causes and risk

It is autosomal dominant, but 50% are the result of new mutations.

How it presents

• Cafe au lait spots: hypermelanotic macules
• Axillary and inguinal freckling: small round hyperpigmented spots in the axilla or inguinal area
• Neurofibromas: multiple subcutaneous papules and macules
• Lisch nodules: hamartomas of the iris, a circumscribed melanotic iris
• Bone involvement: scoliosis, bone dysplasia, pectus excavatum, and limb deformities such as outward bending lower legs and flat feet

Learning disorders and disabilities, abnormal speech development and seizures are common, with a larger than average head size and short stature.