BOF: 3.21
A 35-year-old male is seen in the follow up clinic. He
has an inherited condition for which he attends yearly follow up.
On examination, he has 8 café-au-lait macules of over 15
mm in greatest diameter on his trunk, he has multiple discrete skin nodules
distributed over his trunk and limbs and there is freckling in the axillae.
The patient is worried about his child; a boy of 6. He
was told that examination of the child could conclusively exclude inheritance
of this condition in the child but he has forgotten what the exclusion
criteria were. He asks you to reiterate them and your reply is that this
condition may be confidently excluded if:
a)
The child does not have any café-au-lait macules
b)
If the child has fewer than 6 café-au-lait spots
c)
If the child has no axillary freckling
d)
If the child has no skin nodules
e)
If no member of the mother’s family have been affected
Answer: a)
This patient has an inherited condition. There are
several conditions where localised hyperpigmentation is associated with
systemic disease. Multiple café-au-lait spots are seen in neurofibromatosis
ACES for PACES Page 115
Skin nodules are seen in many conditions;
neurofibromatosis is one of them.
ACES for PACES Page 133
Axillary freckling too is a feature of neurofibromatosis
ACES for PACES Page 152
NF1
The diagnosis of neurofibromatosis type 1 (NF1) may be
made in the presence of 2 or more of the following features:
·
Six or more café-au-lait spots of more than 5 mm in greatest
diameter in pre-pubertal individuals and more than 15 mm in greatest diameter
in post-pubertal individuals.
·
2 or more peripheral neurofibroma or one plexiform neurofibroma
·
Freckling in the axillary or inguinal regions
·
Optic glioma
·
2 or more iris hamartoma (Lisch nodules)
·
An osseous lesion such as sphenoid dysplasia or thinning of the
long bone cortex with or without pseudoarthrosis
·
A first degree relative (parent, sibling or offspring) with NF1
Peripheral neurofibroma may be skin nodules (dermal
neurofibroma) or nodular neurofibroma on major peripheral nerve trunks.
Neurofibromatosis is inherited as an autosomal dominant
condition. Inheritance is 100 % and in children of affected parents, the
absence of café-au-lait spots by the age of 5 excludes the condition. Rare
families have less than six café-au-lait spots and 10% of the general
population have one or two spots hence having less than 6 spots does not
exclude it.
Dermal neurofibromas are unusual until the late teens or
early twenties and hence their absence does not exclude this condition.
Axillary freckling usually develops after age 7
As it is an autosomal dominant condition and one parent
is affected the other parent need not be affected
Revision Tip
Revise neurofibromatosis KEYS to
SUCCESS in Medicine page 483-484
