"Noonan Syndrome" – What Is It?
Noonan syndrome is a hereditary disorder of physical development (see below), which is also associated with learning disorders and a slightly increased risk of cancer. There are various special forms of Noonan syndrome or Noonan syndrome-like disorders:
Noonan syndrome with multiple lentigines: Besides the typical Noonan syndrome changes, dark spots (lentigines) are found on the skin. Those affected are often hard of hearing and typically have particular heart defects (hypertrophic cardiomyopathy).
Noonan syndrome-like disorder with loose anagen hair: Those affected have changes typical of Noonan syndrome but are slightly darker pigmented and have loose hair.
CBL syndrome: In this Noonan syndrome-like disease, the typical Noonan changes are mild and easily overlooked. Patients can develop vascular inflammation (vasculitis) and have a high risk of developing a malignant blood disease in childhood (juvenile myelomonocytic leukemia).
How Is "Noonan Syndrome" Diagnosed?
People with Noonan syndrome show typical characteristics that can be recognized, for example, by experienced human geneticists, pediatricians, or other people with experience of this disorder. The following changes are variably present:
- Striking facial features with low-set, backward-rotated ears
- Wide-set eyes
- Drooping eyelid
- Short stature
- Wide neck with low hairline
- Congenital heart defects (especially pulmonary stenosis hypertrophic cardiomyopathy)
- Chest deformity
- Skin and hair changes
- Vision problems
- Undescended testicles
- Learning problems
- Bleeding tendency
After a suspected clinical diagnosis, a genetic test can be carried out to confirm the diagnosis. This is successful in the vast majority of cases.
What Is the Risk of Cancer?
Children with Noonan syndrome have an approximately 8-fold increased risk of cancer. As cancer in children is sporadic, it is still comparatively rare, and the majority of children with Noonan syndrome do not develop cancer. The cancer spectrum includes the following types of cancer (selection): Low-grade glioma (a comparatively benign brain tumor), acute leukemia, neuroblastoma, and rhabdomyosarcoma.
Specific mutations in PTPN11 are associated with an increased risk of excessive blood formation during the first months of life. Occasionally, this so-called myeloproliferative takes an aggressive course, and therapy is indicated. Here, it is important to consult experienced pediatric oncologists.
Noonan syndrome-like CBL syndrome, is associated with a high risk of juvenile myelomonocytic leukemia. Although this is malignant, not all those affected need treatment, as the clinical course can be benign. Here, too, an experienced pediatric oncologist must be consulted.
What Is Known About the Development of "Noonan Syndrome" ?
A hereditary mutation in the RAS signaling pathway gene causes Noonan syndrome. The following genes can be affected: PTPN11, SOS1, RAF1, RIT1, KRAS, NRAS, BRAF, MAP2K1, RRAS, RASA2, A2ML1, SOS2, LZTR1, CBL, SHOC2, PPP1CB.
Is There Any Form of Treatment Available?
There is no therapy for Noonan syndrome itself. However, it makes sense to address the individual problems associated with Noonan syndrome (heart, hearing, vision, etc.) with the treatment team and promote learning in particular.
If cancer occurs, the therapy should be discussed with the respective study director. Aggressive therapy may not be necessary in children with juvenile myelomonocytic leukemia. However, this should be decided individually and in consultation with the EWOG-MDS study.
Diagnosis of " Noonan Syndrome" What's Next?
If you have been diagnosed with this cancer predisposition syndrome, it is important to see a specialist. The following section explains whether cancer screening tests or other measures are needed and how they should be carried out. We also give you some valuable tips on what you can do yourself. If you have any questions, please do not hesitate to contact us or your doctor.
Diagnosis of " Noonan Syndrome" What's Next?
If you have been diagnosed with this cancer predisposition syndrome, it is important to see a specialist. The following section explains whether cancer screening tests or other measures are needed and how they should be carried out. We also give you some valuable tips on what you can do yourself. If you have any questions, please do not hesitate to contact us or your doctor.
Medical Measures for Early Detection
As the risk of cancer is only mildly increased, no general early detection measures are necessary. However, if medical problems arise, they should be clarified quickly.
In children aged 0 to 5 years with a risk of excessive blood formation (particularly PTPN11 or KRAS mutations) or in children with CBL syndrome, the following early diagnosis can be offered: Physical examination with particular attention to spleen size and blood count with differentiation every 3-6 months.
Noonan Syndrome- What You Can Do Yourself
You Should Pay Attention to This
If your child feels unwell, is listless, exhausted, or pale, has a palpable change or an unusually bulging abdomen, or if you notice anything else unusual, you should seek clarification as soon as possible.
Further Information
Patients can also register for the CPS registry at any time or have this done by the doctors looking after them.
Any further questions?
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