Story of a 38 month-old girl diagnosed with Coffin-Siris syndrome after more than 3 years of her diagnostic odyssey

The cover of 'Story of a girl with Coffin-Siris syndrome'

Her Story

A baby girl born with Coffin-Siris syndrome at 39 weeks of gestation is smiling in a diaper.

A girl was born at 39 weeks of gestation from healthy, nonconsanguineous parents.
She weighed 2.4kg (5.3lb) (under 3rd percentile), showing no signs of any problems.

First Visit

A girl in blue dress and her four major symptoms
When she was five months old, she visited the hospital for her poor weight gain and neurodevelopmental delay.

  • Height 63cm (2.1’) (4th percentile)
  • Weight 5.5kg (12.1lb) (7th percentile)
  • Head circumference 40.5cm (15.9”) (17th percentile)

At the point, the doctor was able to observe an unusually high and narrow palate, horizontally trembling eye movement, axial hypotonia with severe head lag and cave-in shaped chest.

First Examinations

A female doctor holding a brain MRI result and taking a close look at the result, indicating agenesis of the corpus callosum.
To examine the cause of her symptoms, the doctor conducted a brain MRI.
The result revealed complete agenesis of the corpus callosum.

The doctor also used chromosome analysis and chromosomal microarray analysis, but both results found nothing.

Visit at 24 months

Two symptoms the girl with Coffin-Siris syndrome is presenting
The second visit at her 24 month-old showed the progression of her developmental delay.
She was unable to walk without support with a broad ataxic gait and was unable to make eye contact with others.

Visit at 38 months

Symptoms of the girl with Coffin-Siris syndrome at 38-month-old
When she visited the hospital at 38 months, she was at the same level of development as an 8-month-old child.

She was unable to speak with meaningful words and was only able to sit, not walk.
It was hard to pinpoint the disease with these symptoms.

Ending Her Diagnostic Odyssey

After the visit, she was tested for a whole exome sequencing with 3billion to find the genetic cause behind her conditions.

The test found a pathogenic variant on her ARID1B gene.

However, her parents’ variant-specific tests of the gene have shown no mutation on the gene, indicating that the girl’s genetic variant was ‘de novo.’

The girl was finally diagnosed with Coffin-Siris Syndrome 1.

For detailed information of the disease including the inheritance pattern, please visit Rare Disease Series #: Coffin-Siris syndrome.


  1. ic_Disease-7
  2. Disease:
    Disease: Coffin siris syndrome 1 (MIM# 135900)
    Gene: ARID1B

  1. ic_treatments-1
  2. For detailed information, please refer to Rare Disease Series #7: Coffin Siris Syndrome.

    After diagnosis, she is currently undergoing rehabilitation treatment for her developmental delays.
Stay tuned for 3billion’s next 'My Odyssey' series. We will deliver more diagnostic stories of patients diagnosed with us. Thank you.