Legius syndrome is a rare genetic
condition. It is one in a group of conditions called RASopathies
(raz-OP-uh-thees). These happen when there's a problem in the way cells in the body
Legius syndrome (LEE-jus SIN-drome) can cause brown spots on the skin, freckles
in the armpits, and learning problems. Kids with the condition can manage its symptoms
with regular medical care, and have no limits on their activities.
It's also known as neurofibromatosis type 1-like syndrome (NF1-like syndrome).
What Are the Signs & Symptoms of Legius Syndrome?
A child with Legius syndrome often has these signs:
café-au-lait spots (named for their color, meaning "coffee with milk")
darker than surrounding skin
more than 1/4-inch (5 millimeters) across
usually visible by the time the child is 1 year old
freckles in the armpits or in the crease between the child's belly and hip (the
inguinal fold) by age 6
The signs and symptoms of Legius syndrome can look like those of a more serious
genetic problem called neurofibromatosis.
What Causes Legius Syndrome?
Legius syndrome happens because of a change (mutation) in a gene that cells use
to make a protein that:
helps control how cells grow
affects a growth-control system in the RAS pathway
Sometimes, Legius syndrome 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 called a new mutation.
How Is Legius Syndrome Diagnosed?
At birth, the delivery team may notice the baby's wide-set eyes and suggest genetic testing. But in
most cases, doctors find the condition only after other signs happen, such as café-au-lait
To make the diagnosis, the doctor will:
ask about the child's symptoms and signs
ask about the family history of genetic conditions
do an exam
do genetic testing
Doctors may look for brain and bone problems by doing X-rays or an MRI.
How Is Legius Syndrome Treated?
Often, it's a genetics doctor who diagnoses a child with Legius syndrome. But follow-up
care usually is routine, and managed by a pediatrician or family practice doctor.
There's no cure for Legius syndrome. Treatment focuses on managing the symptoms,
and may include: