Coffin–Siris syndrome

Coffin–Siris syndrome
Synonyms	Dwarfism-Onychodysplasia, Fifth Digit Syndrome, Mental Retardation with Hypoplastic 5th Fingernails and Toenails, Short Stature-Onychodysplasia
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Field	Medical genetics, Pediatrics
Symptoms	Developmental delay, intellectual disability, coarse facial features, hypotonia, absent or hypoplastic nails on the fifth digits
Complications	Delayed motor and language skills, feeding difficulties, respiratory infections, possible seizures
Onset	Congenital (present at birth)
Duration	Lifelong
Types	Multiple subtypes associated with different gene mutations (e.g. ARID1B, SOX11, ARID2)
Causes	Genetic mutation (commonly de novo), especially in genes related to the SWI/SNF chromatin remodeling complex
Risks	Sporadic (de novo) or inherited in an autosomal dominant pattern
Diagnosis	Clinical diagnosis supported by genetic testing
Differential diagnosis	Nicolaides–Baraitser syndrome, Brachymorphism-Onychodysplasia-Dysphalangism syndrome
Prevention	None known
Treatment	Symptomatic and supportive: physical therapy, occupational therapy, speech therapy, special education
Medication	As needed for comorbidities (e.g., anticonvulsants for seizures)
Prognosis	Varies; many children can live into adulthood with supportive care
Frequency	Fewer than 100 cases reported in literature
Deaths	Rare; depends on severity and complications

Boy with Coffin–Siris syndrome showing typical features

Illustration of de novo mutations associated with rare genetic disorders

Coffin–Siris syndrome (CSS) is a rare genetic disorder characterized by developmental delay, intellectual disability, hypoplasia or aplasia of the nails on the fifth fingers and toes, and distinctive facial features. First described in 1970 by Grange S. Coffin and Evelyn Siris, the syndrome has since been linked to mutations in multiple genes, most commonly those encoding components of the SWI/SNF chromatin remodeling complex.

Clinical Features

The syndrome has a broad spectrum of symptoms that can range from mild to severe. Common clinical features include:

• Developmental delay or intellectual disability
• Short or absent fifth fingers and toes with nail hypoplasia or aplasia
• Low birth weight
• Feeding difficulties in infancy
• Recurrent respiratory infections
• Hypotonia
• Joint laxity
• Delayed bone age
• Microcephaly
• Coarse facial features:
  • Wide nasal bridge and tip
  • Wide mouth
  • Thick eyebrows and eyelashes
  • Hypertrichosis (excessive hair)

Causes

Coffin–Siris syndrome is most commonly caused by de novo mutations in genes related to chromatin remodeling. These include:

• ARID1B – the most commonly mutated gene in CSS
• SOX11
• ARID2
• Additional genes include: SMARCA4, SMARCB1, SMARCE1, and SMARCA2

The condition is typically inherited in an autosomal dominant fashion, though most cases are sporadic and arise from a de novo mutation.

Genetics

All known causative genes are involved in the function of the SWI/SNF chromatin remodeling complex, which regulates gene expression by altering chromatin structure. Disruption of this complex affects multiple developmental pathways, leading to the wide range of observed symptoms.

Diagnosis

Diagnosis is primarily clinical and based on:

• Presence of distinctive phenotypic features
• Developmental and intellectual assessment
• Absent or underdeveloped fifth digit nails

Confirmation is achieved through molecular genetic testing, typically using whole exome sequencing or targeted gene panels for SWI/SNF complex mutations.

Differential Diagnosis

Conditions that may mimic Coffin–Siris syndrome and should be considered in the differential include:

• Nicolaides–Baraitser syndrome
• Rubinstein–Taybi syndrome
• Brachymorphism-Onychodysplasia-Dysphalangism syndrome
• DOOR syndrome

Treatment

There is no cure for Coffin–Siris syndrome. Treatment is symptomatic and supportive:

• Physical therapy to improve motor function
• Occupational therapy for fine motor skills
• Speech therapy for language development
• Special education services
• Regular screening for complications such as seizures and hearing loss

Prognosis

The prognosis depends on the severity of symptoms and associated complications. With appropriate therapies and support, many individuals achieve varying degrees of independence. Severe cases with associated anomalies may have a more guarded prognosis.

Epidemiology

Coffin–Siris syndrome is extremely rare. Fewer than 100 cases have been reported in the medical literature. Due to variable expression and overlap with other syndromes, it may be underdiagnosed.

See also

• Nicolaides–Baraitser syndrome
• ARID1B
• Developmental disorder
• Genetic testing
• Syndromic intellectual disability

External Links

• Orphanet entry on Coffin–Siris syndrome
• GeneReviews: Coffin–Siris Syndrome
• GeneCards entry for ARID1B