Costello Syndrome

What Is Costello Syndrome?

Costello syndrome is a genetic disorder that is a part of a larger group of conditions called RASopathies. RASopathies arise when something goes wrong in a pathway involved in the way the cells of our bodies communicate the information they need to function properly. Since the cells of our bodies make up our tissues, organs and organ systems, RASopathies can have widespread effects on growth, development and health.

Costello syndrome is the rarest of the RASopathies with less than 300 people with this diagnosis worldwide. It is estimated to occur in about 1 in 300,000 to 1 in 1.25 million live births. It is not inherited from either parent. The genetic change that causes Costello syndrome is brand new (de novo), having occurred for the first time in the person affected by the condition.

What Causes Costello Syndrome?

Costello syndrome occurs due to a genetic change (sometimes called a mutation or genetic variant) in HRAS gene. A genetic change is not identified in about 10 to 20% of people diagnosed with Costello syndrome. We are still learning new information about the causes of Costello syndrome.

Costello syndrome is a dominant condition, meaning that a person with Costello syndrome has a 50% chance of passing the syndrome on to a child. However, 80 to 90% of cases of Costello syndrome appear in families with no prior history of it.

What Are the Signs & Symptoms of Costello Syndrome?

Costello syndrome is typically diagnosed in infancy or childhood. Some signs may appear as early as during pregnancy. The specific features of Costello syndrome each person has can be different, even within the same family. The most common features are intellectual disability, distinctive facial features such as a large mouth with full lips, excessive wrinkling of the skin over the backs of the hands and feet, and deep palmar (of the palm of the hand) and plantar (bottom of the foot) creases. Below is a more complete summary of the most frequent signs and symptoms—many of which a person with Costello syndrome may not develop or present with at all. 

How Is Costello Syndrome Diagnosed?

A doctor who specializes in this disorder will complete the evaluation to confirm a diagnosis of Costello syndrome. It is diagnosed using the clinical features in the picture above and then often confirmed with genetic testing. Genetic testing is done on a blood sample from the child. The purpose is to identify the specific change in the HRAS gene.

How Is Costello Syndrome Treated?

There is no single treatment or cure for Costello syndrome. Treatment plans are created by a healthcare team with input from the patient and their family. Some symptoms may require more regular follow-up with specialists than others. This team may include specialists like doctors who are pediatricians, geneticists, oncologists, neurologists, cardiologists, orthopedic surgeons, and dermatologists.

The management and treatment of the signs and symptoms of Costello syndrome may involve medicines, management of diet and nutrition, medical procedures and/or surgeries, social support, and work with speech, physical, and/or occupational therapists.

Early intervention programs are a useful support resource to help address the developmental differences often seen in children with Costello syndrome. In some cases, children with Costello syndrome need extra support in school and would benefit from an individualized education program (IEP).

Meeting and following up with a genetic counselor can help families better understand Costello syndrome and connect them with useful support resources.

What Are the Long-Term Effects of Costello Syndrome?

One of the reasons it is important to confirm a diagnosis of Costello syndrome as early as possible is because the condition varies widely from person to person. As a result, the life expectancy also differs among people who have Costello syndrome. Congenital heart defects can be a major cause of shortened life expectancies and death. Additionally, people with Costello syndrome have a chance of developing cancerous tumors over the course of their lifetime. The life expectancy of a person with this condition has not yet been formally studied.


Our team works closely with researchers who study RASopathies, like Costello syndrome. Thus, we are informed of cutting-edge treatment and technology that may benefit the children in our care. We can connect interested children and families with opportunities to participate in research studies that can help us better understand the RASopathies and possibly contribute to the discovery of future therapies.

Appointment/Referral Information

To schedule a first-time or return appointment, please call the Division of Genetics directly at 312.227.6120.


For more information, please call our Clinic Coordinator, Carolyn Raski at 312.227.4391.


Costello syndrome can bring medical challenges and significant stress in the lives of those who know and love someone with the condition. The below groups and research-based resources can help provide support for families and those affected by Costello syndrome.

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