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Costello Syndrome

What is Costello Syndrome?

Costello syndrome is a rare genetic condition that affects about 300 people in the world.

Common features include:

  • Congenital heart disease
  • Characteristic facial features
  • Skeletal abnormalities
  • Malignant tumors

All people with Costello syndrome have intellectual disabilities. This often ranges from mild to moderate impairment.

Common Issues with Costello Syndrome

Heart Issues

The most common heart defect seen in those with Costello syndrome is hypertrophic cardiomyopathy. This is a thickening of the heart which causes the heart muscle to not work as well. Other types of heart defects include:

Muscle and Skeletal Abnormalities

Many with Costello syndrome have:

  • Decreased muscle tone (hypotonia)
  • Loose / flexible joints
  • Abnormal curvature of the spine (kyphoscoliosis)
  • Short stature

They also have:

  • An abnormality in their wrists and fingers (ulnar deviation)
  • Differences in the shape of their chest (pectus carinatum/excavatum)
  • Developmental hip dysplasia
  • Low bone density (osteoporosis or osteopenia)

Physical Features

People with Costello syndrome have distinct facial features such as a long face, full lips, and low-set ears, which can change over time. They may also have a large head (macrocephaly). Though those with Costello syndrome share many facial features, they also look like their own family members.

They also often have fine, curly hair and a deep, hoarse or whispery voice.

Learning and Development

Delay in reaching early developmental milestones is common for those with Costello syndrome. Infants often have trouble feeding due to low muscle tone (hypotonia). All people with Costello syndrome will have some intellectual disabilities, ranging from mild to moderate.

Other Issues

People with Costello syndrome can also have:

  • Benign growths (papillomata) on their face and near their genitals
  • Malignant tumors in their heart (rhabdomyosarcoma) and brain (neuroblastoma)
  • Transitional cell carcinoma of the bladder
  • Buildup of fluid in the brain (hydrocephalus) and seizures
  • Structural abnormalities of the brain called a Chiari 1 malformation

Diagnosis and Genetics of Costello Syndrome

Costello is diagnosed by a doctor who is familiar with this condition. The evaluation should include:

  • Detailed family history
  • Medical history
  • Physical exam

Genetic testing is also useful in making this diagnosis. The majority of patients with Costello syndrome have a change (mutation) in the HRAS gene.

Typically each person has two copies of each gene in their genetic make-up. One copy of the HRAS gene is passed down from their father and the other copy is passed down from their mother. With Costello syndrome, a person has a change (mutation) in one copy of the HRAS gene. Males and females are equally affected. Typically, the mutation happens for the first time in that person and there is no family history of the condition.

Most people with Costello syndrome do not have children. If someone with Costello syndrome were to reproduce, they would have a 50%, or a 1 in 2 chance, of passing the condition to each of their future children.

Treatment and Management


There is no “cure” for Costello syndrome, but there are treatments and therapies. Each treatment plan is tailored to the patient, based on their medical issues.

  • For those with heart issues, treatment is similar to people who have the same heart defect but do not have Costello syndrome.
  • For those with delayed development, early treatments may include physical, occupational, and / or speech therapy.
  • Children may need an Individualized Education Plan (IEP) in school.
  • Infants with severe feeding issues may need surgery and / or use of tube feeding
  • Some people with delayed growth may need growth hormone therapy.
  • Those with neurological symptoms may need surgery.


Children should see their doctor on a routine basis so they can:

  • Get additional testing (ultrasounds and urinalysis) to screen for tumors
  • Check their growth and development
  • Check for neurological symptoms, seizures and skeletal problems

Prognosis for Patients with Costello Syndrome

Costello syndrome is a lifelong condition. Life expectancy often depends on how severe the heart defect is. It also depends on the other medical complications the patient has.

Costello Syndrome Resources

RASopathy Network

Costello Syndrome Family Network

International Costello Syndrome Support Group

Last Updated 12/2022

Reviewed By Liz Bombal, MS, Genetic Counselor

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