Understanding Skeletal Dysplasia

Skeletal Dysplasia: What It Is and Why It Matters

Skeletal dysplasia is a group of more than 450 disorders that affect the development, growth, and structure of bones and cartilage. These conditions are often referred to as “dwarfism” or “short-limb” conditions, though they vary greatly in severity from mild differences in stature to life-limiting or fatal abnormalities that affect organ development.

In the case of Becca’s daughter Savannah, the condition was thanatophoric dysplasia, a rare and severe form of skeletal dysplasia that affects fetal development and is considered incompatible with life.

 

What Is Thanatophoric Dysplasia?

Thanatophoric dysplasia (TD) is a lethal skeletal disorder, usually caused by a random mutation in the FGFR3 gene. The word “thanatophoric” comes from the Greek word for “death bearing.” Although it is a deeply difficult diagnosis to hear, understanding it is key for any family navigating these waters.

 

There are two types of TD:

• Type I: Characterised by extremely short limbs (especially femurs that may be curved), a narrow chest, and normal skull shape.

• Type II: Features a similar body structure but with a distinct cloverleaf-shaped skull due to premature fusion of the skull bones.

 

Savannah was diagnosed with features of Type II, including:

• Extremely short and curved long bones (femur and humerus)

• Constricted chest cavity, leaving no room for lung development

• A cloverleaf skull deformity (known as kleeblattschädel), visible in advanced ultrasounds

• Underdeveloped or absent lungs (pulmonary hypoplasia)

• Excess amniotic fluid (polyhydramnios), caused by impaired fetal swallowing

 

These anomalies are typically incompatible with life outside the womb.

 

When Is Skeletal Dysplasia Diagnosed?

Many skeletal dysplasias are detected in the second trimester, typically between 18 and 24 weeks, during the routine anatomy scan. Measurements of the long bones, chest, and head are key indicators. In Becca’s case, Savannah’s anatomy scan was delayed from 20 to 24 weeks. This delay significantly altered their window of understanding and options for care.

 

Signs that may raise suspicion of TD include:

• Shortened or curved femur/humerus

• Narrow chest and short ribs

• Large or misshapen head

• Poor ossification (bone hardening) in the spine or skull

• Accumulation of fluid or polyhydramnios

 

What Happens After Diagnosis?

Once a condition like TD is suspected, referral to a Maternal Fetal Medicine (MFM) specialist is essential. These specialists perform more detailed scans and measurements, offer genetic testing, and help families understand their options.

In Savannah’s case, a lethality checklist was used to assess limb length, head-to-chest ratio, lung development and other indicators which confirmed the condition was life-limiting.

 

Families facing this diagnosis are often given heartbreaking choices:

• Continue the pregnancy and provide comfort/palliative care after birth

• Consider Termination for Medical Reasons (TFMR) where legally permitted

• Create a birth and memory plan with the support of palliative care or baby hospice groups

 

What Causes Thanatophoric Dysplasia?

TD is caused by a spontaneous mutation in the FGFR3 gene and is not inherited. The mutation occurs randomly and is not the result of anything the parents did or didn’t do.

This is crucial for grieving parents to understand:

It is not your fault.

Parents who have experienced TD are often told that the chance of it happening again is less than 2%.

 

Support and Resources

Receiving a diagnosis of skeletal dysplasia, especially a lethal form like TD, can be devastating. But you are not alone.

 

Becca found support through:

• Sufficient Grace Ministries – offering bereavement doulas and birth support

• The Chrysanthemum Project – providing postpartum care kits to loss parents

• Online groups for skeletal dysplasia and TFMR support

• Peer-to-peer connections with other loss parents

 

With love and compassion,

Rosie x