Short answer · Medically reviewed summary · Last updated: 2026-05-08
Costello syndrome is a rare genetic condition caused by a germline mutation in the HRAS gene, which leads to the overactivation of the RAS/MAPK signaling pathway. This condition is typically inherited in an autosomal dominant pattern, though most cases arise from a new (de novo) mutation rather than being passed down from parents. What causes Costello syndrome at the genetic level? The primary cause of Costello syndrome is a mutation in the HRAS gene, located on chromosome 11.
Which are the causes of Costello Syndrome?
Causes of Costello Syndrome explained: genetic and environmental factors, reviewed against medical sources, plus patient perspectives.
Costello syndrome is a rare genetic condition caused by a germline mutation in the HRAS gene, which leads to the overactivation of the RAS/MAPK signaling pathway. This condition is typically inherited in an autosomal dominant pattern, though most cases arise from a new (de novo) mutation rather than being passed down from parents.
What causes Costello syndrome at the genetic level?
The primary cause of Costello syndrome is a mutation in the HRAS gene, located on chromosome 11. Think of the HRAS gene as a master switch that sends signals to cells telling them when to grow and divide. In Costello syndrome, this switch becomes "stuck" in the "on" position. This constant signaling causes cells to proliferate abnormally, which explains the characteristic physical features, developmental delays, and increased risk of tumor development associated with the condition.
Is Costello syndrome hereditary?
While Costello syndrome is a genetic disorder, it is rarely inherited from a parent. In the vast majority of documented cases, the HRAS mutation occurs as a de novo event, meaning it happens spontaneously in the egg or sperm cell at the time of conception. Because the mutation is present in every cell of the body, it is classified as an autosomal dominant condition, meaning a person with Costello syndrome could theoretically pass the mutation to their offspring, though this is clinically uncommon.
What are the key mechanisms involved?
The pathology of Costello syndrome is tied to the RAS/MAPK pathway, a critical communication system in the body. Key aspects of the disease mechanism include:
- Pathway Overactivation: The specific HRAS mutations (most commonly p.Gly12Ser) cause the RAS protein to remain constantly active.
- Developmental Impact: This overactive signaling disrupts normal embryonic development, affecting the heart, skin, and musculoskeletal system.
- Tumorigenesis: Because the body’s "grow" signal is stuck, individuals with Costello syndrome have a statistically higher predisposition to certain benign and malignant tumors, such as rhabdomyosarcoma or bladder cancer.
What is the current state of research?
Researchers are actively studying Costello syndrome to better understand how to modulate the RAS pathway. Current research focuses on targeted therapies that might "turn off" the overactive signaling without harming healthy cellular functions. Understanding these pathways is crucial for the 13 members of our DiseaseMaps community and others worldwide who are seeking more effective monitoring and treatment protocols.
Next steps
- Consult a clinical geneticist for formal testing and confirmation of the HRAS mutation.
- Maintain a rigorous surveillance schedule for tumor screenings as recommended by international guidelines.
- Join the DiseaseMaps.org community to connect with other families navigating this rare diagnosis.
Medical disclaimer: This information is for educational purposes only and should not replace professional medical advice, diagnosis, or treatment.
References
- NIH Genetic and Rare Diseases Information Center (GARD): Costello Syndrome
- Orphanet: Costello Syndrome (ORPHA:209)
- OMIM (Online Mendelian Inheritance in Man): Costello Syndrome (#218040)
- Costello Syndrome Family Network
