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 and be painful. Very large neurofibromas (called plexiform neurofibroma) may 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.
Depending on when the DNA change happened, NF1 can be:
Classic: The NF1 gene change affects all cells in the body.
Mosaic: The body has 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 sometimes look for brain, bone, and other problems using: