curving, thinning, or weakness of the forearms or lower leg bones
freckles in their armpits or in the crease between the belly and hip (groin)
Neurofibromas (ner-oh-fye-BROH-muz) can:
cause appearance problems
turn into cancer
The symptoms of NF1 are mild in some children, but severe in others.
What Causes Neurofibromatosis Type 1?
NF1 and NF2 are part of a group of rare conditions called RASopathies (raz-OP-uh-thees). These happen when there's a problem in the way cells communicate in one of the body's pathways.
Children with neurofibromatosis type 1 have cells that don't make neurofibromin as they should. Neurofibromin is a protein that acts like a brake to stop the RAS pathway and keep cells from growing out of control.
Without working neurofibromin, the cells:
can't shut down the RAS pathway
grow out of control, leading to tumors and other problems
This happens because of a change (mutation) in a gene called NF1.
There are three types of NF1, depending on when the DNA change happened:
Classic: The NF1 gene change (mutation) affects all cells in the child's body.
Mosaic: The child's body is a mix of cells with and without the NF1 gene change.
Segmental: The NF1 symptoms are in one part of the body.
Sometimes, NF1 runs in families. A parent who has it has a 50% chance of passing it to a child. Other times, the change is "spontaneous." This means that a child has the condition but the parents do not. This is called a new mutation.
How Is Neurofibromatosis Type 1 Diagnosed?
NF1 may be diagnosed before or at birth using genetic (DNA) tests. A doctor usually suggests genetic testing for NF1 if:
a parent or sibling of an unborn baby is known to have NF1
a newborn shows signs of NF1
Most children with NF1 are diagnosed only after several café-au-lait spots appear. A doctor usually will:
ask about the child's symptoms and whether family members have similar symptoms
consider NF1 and other conditions that can cause café-au-lait spots
The doctor will do an exam and may work with a team of specialists who diagnose and treat children with NF1, including:
an ophthalmologist, who will check for:
a tumor (an optic glioma) on the nerve from the eye to the brain
small spots (called Lisch nodules) on the colored part (iris) of the eye
a geneticist who will test for the gene changes that can cause NF1
When doctors suspect a child has NF1, they usually look for brain, bone, and other problems using: