What is Coffin Siris Syndrome

Coffin-Siris syndrome is a rare genetic disorder characterized by developmental delays, intellectual disability, and distinctive physical features, most notably the underdevelopment or absence of the fifth (pinky) fingernails and toenails. It is caused by mutations in genes involved in the BAF chromatin remodeling complex, which regulates how DNA is packaged and expressed within cells.

What are the primary symptoms of Coffin-Siris syndrome?

While the clinical presentation of Coffin-Siris syndrome varies significantly between individuals, the condition frequently affects multiple body systems. Common clinical features include:

• Skeletal abnormalities: Hypoplasia (underdevelopment) of the distal phalanges and nails, particularly the fifth digit.


• Craniofacial features: A wide mouth, thick lips, bushy eyebrows, and a broad nasal bridge.


• Developmental impact: Delayed motor milestones, speech delays, and varying degrees of intellectual disability.


• Systemic involvement: Potential challenges with feeding, vision, hearing, and structural heart or kidney defects.

How common is Coffin-Siris syndrome?

Coffin-Siris syndrome is considered a very rare condition. While the exact prevalence is unknown, more than 200 cases have been documented in medical literature. Within the DiseaseMaps.org community, 212 people with Coffin-Siris syndrome have connected to share their experiences, highlighting the importance of global registries in understanding this rare diagnosis.

What causes Coffin-Siris syndrome?

Coffin-Siris syndrome is caused by pathogenic variants in genes that encode subunits of the BAF (SWI/SNF) chromatin remodeling complex, such as ARID1A, ARID1B, SMARCA4, and SMARCE1. Most cases occur sporadically (de novo), meaning the genetic change happens for the first time in the affected individual and is not inherited from parents. However, autosomal dominant inheritance has been reported in rare instances.

How is Coffin-Siris syndrome distinguished from other conditions?

Coffin-Siris syndrome is often compared to other "intellectual disability-malformation" syndromes. It is clinically differentiated by the specific combination of nail hypoplasia and characteristic facial dysmorphism. Genetic testing—specifically chromosomal microarray or multigene panel sequencing—is the gold standard for confirming a diagnosis of Coffin-Siris syndrome and distinguishing it from phenotypically similar disorders like Nicolaides-Baraitser syndrome.

Next steps

• Consult with a clinical geneticist to discuss molecular testing options.


• Schedule evaluations with a multidisciplinary team, including a cardiologist, ophthalmologist, and developmental pediatrician.


• Join the DiseaseMaps.org community to connect with other families navigating the journey of Coffin-Siris syndrome.

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): Coffin-Siris Syndrome.


• Orphanet: Coffin-Siris Syndrome (ORPHA:199).


• OMIM (Online Mendelian Inheritance in Man): #135900.


• Coffin-Siris Syndrome Foundation: Patient and family support resources.