Costello Syndrome

You are not alone! 

Costello syndrome is one of the rarest of the rare syndromes and is estimated to occur in 1 out of every 382,000 births. Even though this syndrome is seriously rare, we are here for you if you are seeking support and information.  We are an active network of families who are willing to share and help.  We understand much of what you are going through, because we’ve walked the same path.

Costello syndrome can affect every system in the body, resulting in complex and critical health and developmental needs. The Costello Syndrome Family Network (CSFN) works hard to connect every family of a person with Costello syndrome with the information and support needed to lead optimal lives; to raise awareness among physicians, researchers and the general public; and to support relevant research.

This parent booklet is very helpful to guide you through various systems that are affected due to Costello syndrome:
Click here for a copy of the parent booklet.

Click here for a more detailed review on the management of Costello syndrome.
Click here for a deeper explanation of the genetics in lay terms.

 Quick Facts about Costello syndrome:

  • Costello syndrome (CS) is a rare, genetic disorder that affects many parts of the body.  There is no cure.
  • Costello syndrome causes neurocognitive delays and impaired learning.
  • Many children struggle to walk, talk, and feed themselves.
  • Although infants with Costello syndrome may be large at birth, they have difficulty feeding and grow more slowly than other infants.  They may require a feeding tube as infants but are often able to eat on their own as they grow.
  • Many people with Costello syndrome have Gastroesophageal Reflux Disease (GERD).
  • Problems with the heart are common. About 85% of those with CS have at least one issue with their heart.
  • Beginning in early childhood, people with Costello syndrome have a greater risk of developing cancerous (malignant) and noncancerous (benign) tumors.  Individuals with CS have a 15% lifetime risk of developing malignant tumors, with the highest risk occurring during childhood.  Noncancerous (benign) papillomas and cancerous (malignant) tumors may occur in a muscle, nerve cells, or bladder. Rhabdomyosarcoma, neuroblastoma, and bladder carcinoma are the most common malignant tumors seen in people with CS.
  • Most people with CS will have skeletal and orthopedic problems.


Other characteristics of Costello syndrome include:

  • Short stature (many children have growth hormone deficiency).
  • Distinctive facial feature such as a broad mouth with thick lips, loose folds of extra skin (especially on the hands and feet), and unusually flexible joints.
  • Remarkably pleasant, social, and easy-going personality.


A few more facts:

  • In 2005 a group of Japanese researchers discovered that mutations in a gene called HRAS causes Costello syndrome. HRAS is a gene that has been known for a long time because mutations in it are common in cancers in the general population. It was a surprise that a cancer-associated gene like HRAS could cause a developmental syndrome.
  • Costello syndrome is a part of a group of rare genetic conditions caused by mutations in genes of the Ras-MAPK pathway.  Abnormalities of this pathway cause one of several related syndromes including: Cardio-Facio-Cutaneous (CFC), Costello (CS), Legius (LS), Neurofibromatosis type 1 (NF1), Noonan (NS), and Noonan with Multiple Lentigines (NSML, formerly called LEOPARD syndrome).  These are a part of a group of syndromes called RASopathies that share clinical features such as distinct facial features, developmental delays, cardiac defects, growth delays, neurologic issues, and gastrointestinal difficulties. While these individual syndromes are rare, as a group, the RASopathies are among the most common genetic conditions in the world.
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