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Neurofibromatosis, type 1 (NF1) is characterized by tumors
that grow on or below the skin and in the peripheral nerves.
Physicians use seven criteria to evaluate a patient for
NF1; a confirmed diagnosis requires at least two of the
seven criteria be met. The symptoms of NF1 typically are
apparent during childhood, so if a child reaches age 10
without meeting the criteria, it is unlikely he or she
will develop the disorder. The seven criteria are:
- Six or more café-au-lait spots. Typically
the first indication of NF1, café-au-lait spots
are flat, oval marks that appear on the skin during
infancy or early childhood. The color of the spots
ranges from light tan to dark brown. Children without
NF1 can also have café-au-lait spots.
- Freckling under the arms or in the groin area.
- Two or more dermal neurofibromas or one plexiform
neurofibroma. The benign and usually painless tumors
that form in or under the skin are known as dermal
neurofibromas. They often have a bump-like appearance.
Plexiform neurofibromas grow along and in the peripheral
nerves (which carry messages between the body and
the brain). While they occur less often than dermal
neurofibromas, plexiform neurofibromas can be painful
and quick growing. About 5 percent to 10 percent of
the time, plexiform neurofibromas degenerate into
a malignant type of tumor known as a neurofibrosarcoma.
- Optic nerve glioma. As the name suggests, these
tumors develop on the optic nerve and can result in
decreased vision or sometimes blindness.
- Two or more Lisch nodules. These tiny lumps form
on the iris, the colored part of the eye. They do
not impair vision. They are often detected in older
children and adults with NF1, but are rare in infants
and younger children.
- Orthopaedic abnormalities. Specifically, bowing
of the shin bone or forearm, a misshapen bone (the
sphenoid bone) in the region of the sinuses.
- A first-degree family member (mother, father, sister,
brother), who has NF1.
Other Manifestations
of NF1
In addition to the diagnostic criteria for NF1, this
multisystem disorder can affect the body in other ways.
NF1 is a highly individualized disorder; in a room full
of patients with NF1, some will be mildly affected by
the following conditions; some will be severely affected;
and others will not have the problems at all.
Problems that my occur during childhood, include:
- Learning disabilities. Learning problems are present
in about 40 percent of patients with NF1. Attention
deficit hyperactivity disorder can also be present.
Rarely, individuals with NF1 can have a mild degree
of mental retardation, but more commonly, the problems
are of a nature that once identified, can be successfully
addressed by appropriate learning specialists and
intervention.
- Scoliosis, or curvature of the spine.
- Short stature.
- Macrocephaly, or an abnormally large head, in infants
or young children. This is usually not a problem unless
the growth occurs at a rapid pace.
- Puberty occurring at an early age, also known as
precocious puberty.
In adults, the most common problem is the continual
development of tumors. However, one major concern for
adult NF1 patients is high blood pressure. The cause
of high blood pressure in NF1 patients can be due to
a narrowing of the blood vessels entering the kidney
or a growth on the adrenal gland. In either of these
cases, the typical approaches to lowering blood pressure,
such as a modified diet, exercise, or medicine, will
not get to the root of the problem. Surgery may be necessary
to remove a growth on the adrenal gland; the narrowed
arteries can be opened by surgery or balloon angioplasty
and stenting. Hypertension may be due to the usual causes
in adults as well, but studies should be performed to
check the adrenal glands and renal arteries.
How NF1 is Diagnosed
Clinical tests such as the following can be used for
diagnostic purposes and as a baseline for future evaluations.
- Blood work. A genetic test known as a protein truncation
assay may be ordered but the detection rate is only
between 65 percent to 70 percent. This test is not
routinely performed in order to make the diagnosis
of NF1.
- Imaging studies. There are a number of imaging
studies available, but whether X-ray, magnetic resonance
imaging (MRI) or computed tomography (CT) scan is
used depends on the individual. If there are orthopaedic
concerns, an X-ray may be ordered. An MRI is preferred
for images of the head (including the optic nerves)
and to evaluate plexiform neurofibromas or other internal
lesions. CT scans of the head are also sometimes utilized.
- Slit-lamp examination. A slit lamp enables an ophthalmologist
to examine structures of the eye using high magnification.
For a person who may have NF, a slit-lamp examination
can help detect Lisch nodules on the iris.
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Neurofibromatosis,
Type 1 (NF1)
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