Noonan syndrome: causes, symptoms and treatment

Much of what we are and how we are is determined by our genetic code. The organization of our organism, the rhythm and the way in which our growth and physical development... and even a part of our intellect and our personality is inherited from our ancestors.

However, sometimes genes undergo mutations that, although sometimes they can be innocuous or even positive, sometimes have severe repercussions that hinder to a greater or lesser extent the development and ability to adapt to the environment of those who need it. suffer. One of these genetic disorders is Noonan syndrome..

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Noonan syndrome

Noonan syndrome is a relatively common genetic disorder that occurs in one in every 1,000 to 2,500 births, with a prevalence similar to that of Down syndrome. Is about a disease whose symptomatology can be highly variable depending on the case, but which is characterized by the presence of alterations and delays in development, congenital heart disease, hemorrhagic diathesis and various morphological alterations.

The rate of growth in these children, although it initially seems normative, is severely slowed down, and they tend to have short stature and psychomotor delays. This problem becomes especially evident in adolescence. Sometimes it occurs together with intellectual disability, although this is usually mild. Sensorially they can present vision and hearing problems such as recurrent strabismus or otitis.

At the morphological level, facial alterations such as ocular hypertelorism are appreciated from birth (eyes are too far apart), droopy eyelids, low and rotated ears, neck short. It is also frequent that they present bone alterations in the form of a deformity in the thoracic cage (which can appear in the form of a sunken chest in the area of ​​the sternum or pectus excavatum or in its profusion or pectus carinatum).

One of the most dangerous symptoms is the presence in most patients of heart disease congenital conditions such as pulmonary stenosis or hypertrophic cardiomyopathy, as well as other problems vascular. In addition, the presence of bleeding diathesis is frequent in more than half of the patients, which supposes great difficulties in coagulation that generates that great caution must be taken with the suffering of haemorrhages. They also have great ease of presenting bruises.

Although not so frequent, they can also have lymphatic problems that generate peripheral edema or even in the lungs and intestines. They also tend to be at higher risk for leukemia and other myeloproliferative problems.

In the genitourinary system alterations such as cryptorchidism may appear or no descent of the testicles in males. This causes fertility problems in some cases. However, in the case of women there are usually no alterations in terms of their fertility.

Causes of the syndrome

Noonan syndrome is, as we have already said, a disorder of genetic origin, the main cause of which has been found in the presence of mutations on chromosome 12. Specifically, alterations appear in the form of mutations in the PTPN11 gene in half of the cases, although other genes can also cause it, such as KRAS, RAF1 or SOS1. These are genes that participate in the growth of cells and in their development, with which their alteration causes various alterations in different systems of the organism.

It is generally considered an autosomal dominant disorder that can be inherited from father to son (with transmission from the mother being more frequent), if Well, sometimes the mutations that generate Noonan syndrome appear without any of the parents having transmitted it or there are other cases in the family.

Treatments

There is currently no curative treatment for Noonan syndrome., with existing treatments dedicated to alleviating symptoms, preventing complications, intervening on structural and morphological anomalies, optimize their capacities and offer these people the best quality of life possible.

For this, a multidisciplinary methodology is used with the intervention of different professionals from both medicine and other sciences. The symptoms and alterations presented by those who suffer from this disease can be highly variable, so the treatment will depend on the type of alterations they suffer.

In Noonan syndrome it is essential to carry out regular control and monitoring of the subject's state of health, especially in the probable presence of heart disease. Coagulation problems are not uncommon in this syndrome, so this fact must be taken into account when performing possible surgical interventions. During the first years it may be necessary to use tubes to feed the child. It is not strange that a treatment with growth hormone is used, so that the development of the minor is favored.

At the psychoeducational level, given the high prevalence of learning problems and/or intellectual disability may be required the use of psychostimulation, individualized plans at school, reinforcement of learning basic life skills speech therapy and use of alternative and/or augmentative communication techniques such as the use of pictograms. It may also be necessary to practice physiotherapy to improve his motor skills.

Lastly, genetic counseling should be considered once the subject reaches adolescence or adulthood due to the possibility of transmission of the disorder.

It may also be necessary to use psychological treatment for the subject, since feelings of inadequacy may appear, low self-esteem and depressive syndromes. Likewise, psychoeducation is necessary both for this and for the environment, and attendance at support groups could be useful.

As long as possible complications are controlled, individuals with Noonan syndrome can have a standard of living equivalent to that of people without the disorder. Some of the symptoms may fade with age as they become adults.

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Bibliographic references:

• Ali, O. & Donohoue, P.A. (2016). Noonan syndrome. In: Kliegman, R.M.; Stanton, B.F.; St. Geme, J.W. & Schor, N.F. (eds). Nelson Textbook of Pediatrics. 20th ed. Philadelphia, PA: Elsevier.

• Ballesta, M.J. and Guillén-Navarro, E. (2010). Noonan syndrome, Protoc.diagn.ter.pediatr.; 1;56-63. Virgen de la Arrixaca University Hospital. Murcia.

• Carcavilla, A.; Santome, J.L.; Galbis, L. and Ezquieta, B. (2013). Noonan syndrome. Rev. Esp. Endocrinol. pediatrician; 4 (suppl). Gregorio Marañón General University Hospital. Gregorio Marañón Health Research Institute. Madrid.