Neurocutaneous disorders

Neurofibromatosis type 1 (NF1), initially described by
von Recklinghausen, is one of the most common single gene
disorders, with an incidence of around 1 in 3000. The main
diagnostic features of NF1 are café-au-lait patches, peripheral
neurofibromas and lisch nodules. Café-au-lait patches are
sometimes present at birth, but often appear in the first few
years of life, increasing in size and number. A child at risk who
has no café-au-lait patches by the age of five is extremely
unlikely to be affected. Freckling in the axillae, groins or base
of the neck is common and generally only seen in people with
NF1. Peripheral neurofibromas usually start to appear around
puberty and tend to increase in number through adult life.
The number of neurofibromas varies widely between different
subjects from very few to several hundred. Lisch nodules
(iris hamartomas) are not visible to the naked eye but can be
seen using a slit lamp. Minor features of NF1 include short
stature and macrocephaly. Complications of NF1 are listed
in the box and occur in about one third of affected
individuals. Malignancy (mainly embryonal tumours or
neurosarcomas) occur in about 5% of affected
individuals. Learning disability occurs in about one
third of children, but severe mental retardation in
only 1 to 2%.