Understanding NF1
Plexiform Neurofibromas (PN)

Caleb, age 7, living with NF1 PN, shown here
with his mom. Caleb is not a Koselugo patient.

What is Neurofibromatosis Type 1 (NF1)?

NF1 is a rare genetic disorder that affects nearly 1 in 3000 people worldwide. Individuals with NF1 commonly have tumors along nerves in their body. Plexiform neurofibromas, or PN, are one type of tumor seen in NF1.

What are plexiform neurofibromas (PN)?

PN are noncancerous tumors that can grow along nerves in the body.

PN are commonly seen in people living with NF1.

Up to 50% of children with NF1 have PN.*

*Using whole body magnetic resonance imaging (MRI).

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Where do NF1 PN occur?

PN can grow on any nerve in the body. Regardless of size, any PN may cause symptoms, depending on where it’s located in the body.

As a PN grows, it may cause new or worsening symptoms.

NF1 PN growth may be unpredictable and should not be ignored

PN typically grow fastest in the first 10 years of life, making it important to have a conversation with your child's doctor as early as possible.

Percentage change in target PN volume, Natural History study


The NCI NF1 Natural History study began in 2008 and is an ongoing study. 92 patients with NF1-related PN between the ages 3 and 18 years who had at least 2 volumetric scans were included in the analysis above as the age- and period-matched external control for the SPRINT study.
NCI=National Cancer Institute

How are NF1 plexiform neurofibromas (PN) treated?

Which doctors and healthcare specialists treat pediatric NF1 plexiform neurofibromas (PN)?

Children with NF1 PN are usually seen by specialists who focus on treating symptoms caused by this disease. The location and symptoms of your child's PN will help determine which doctors are best to see for treatment.

By spotting PN early and communicating new or worsening symptoms with your child's doctor, you can help your child get the treatment they need.

Why can’t some NF1 PN be completely removed by surgery?

Surgery for NF1 plexiform neurofibromas may not be recommended by your child’s healthcare provider. One reason is plexiform neurofibromas may be closely intertwined with critical nerves, many blood vessels, and located near major organs. Also, PN may not be completely removed by surgery.

Before Koselugo, there was no FDA-approved medication proven to shrink NF1 PN

Learn about the only FDA-approved treatment option for shrinking NF1 PN

Learn more


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important safety information

What are the possible side effects of Koselugo?

Koselugo may cause serious side effects, including:

  • Heart problems. Koselugo can lower the amount of blood pumped by your heart, which is common and can also be severe. Your healthcare provider will do tests before and during treatment to check how well your heart is working. Tell your healthcare provider right away if you get any of the following signs or symptoms: persistent coughing or wheezing, shortness of breath, swelling of your ankles and feet, tiredness, increased heart rate.
  • Eye problems. Koselugo can cause eye problems that can lead to blindness. Your healthcare provider will check your vision before and during treatment. Tell your healthcare provider right away if you get any of the following signs or symptoms: blurred vision, loss of vision, dark spots in your vision (floaters), other changes to your vision.
  • Severe diarrhea. Diarrhea is common with Koselugo and can also be severe. Tell your healthcare provider right away the first time that you get diarrhea during treatment. Your healthcare provider may give you medicine to help control your diarrhea and may tell you to drink more fluids.
  • Skin rash. Skin rashes are common with Koselugo and can also be severe. Tell your healthcare provider if you get any of the following signs or symptoms: rash that covers a large area of your body, peeling skin, blisters.
  • Muscle problems (rhabdomyolysis). Muscle problems are common with Koselugo and can also be severe. Treatment with Koselugo may increase the level of a muscle enzyme in your blood called creatine phosphokinase (CPK) and may be a sign of muscle damage. Your healthcare provider should do a blood test to check your muscle enzyme levels of CPK before you start taking Koselugo and during treatment. Tell your healthcare provider right away if you get any of the following signs or symptoms: muscle aches or pain; muscle spasms and weakness; dark, reddish urine.

Before taking Koselugo, tell your healthcare provider about all your medical conditions, including if you:

  • have heart problems.
  • have eye problems.
  • have liver problems.
  • are pregnant or plan to become pregnant. Koselugo can harm your unborn baby. Your healthcare provider should verify if you/your partner are pregnant before beginning treatment. Ensure you/your partner use effective birth control (contraception) during treatment and for 1 week after your last dose if there is possibility pregnancy could occur. Tell your healthcare provider right away if you/your partner think you may be pregnant.
  • are breastfeeding or plan to breastfeed. It is not known if Koselugo passes into your breast milk. Do not breastfeed during treatment and for 1 week after your last dose. Talk to your healthcare provider about the best way to feed your baby during this time.

Tell your healthcare provider about all the medicines you take, including prescription, over-the-counter medicines, vitamins, or herbal supplements. Especially tell your healthcare provider if you are taking aspirin, blood thinners, or other medicines to treat blood clots. Koselugo contains vitamin E, which may increase risk of bleeding.

What should I avoid while taking Koselugo?

Do not drink grapefruit juice, eat grapefruit, or take supplements with grapefruit or St. John’s Wort during treatment.

Most common side effects include: vomiting, stomach-area pain, nausea, dry skin, muscle and bone pain, feeling of tiredness or lacking energy, fever, sores in your mouth, headache, redness around the fingernails, itching.

These are not all the possible side effects of Koselugo. Call your healthcare provider for medical advice about side effects. Your healthcare provider may change your dose, temporarily stop, or permanently ask you to stop taking Koselugo if you have any of these side effects. You may report side effects to AstraZeneca at 1-800-236-9933 or at https://
or FDA at
1-800-FDA-1088 or


What is Koselugo?

Koselugo is a prescription medicine that is used to treat children 2 years of age and older with neurofibromatosis type 1 (NF1) who have plexiform neurofibromas that cannot be completely removed by surgery. It is not known if Koselugo is safe and effective in children under 2 years of age.

All families shown in this website have been compensated by Alexion, unless otherwise noted.