Thanatophoric dysplasia

Last revised by Ashesh Ishwarlal Ranchod on 9 Oct 2023

Thanatophoric dysplasia is a lethal skeletal dysplasia. It is the most common lethal skeletal dysplasia followed by osteogenesis imperfecta type II. 

The estimated incidence is around 1:25,000-50,000 3.

There are two recognized subtypes:

  • type I

    • marked underdevelopment of the skeleton

    • telephone handle femurs are more pronounced

  • type II

    • the presence of a cloverleaf skull may be a distinctive feature

    • limb shortening milder and bowing is not a feature 3

It results from a mutation coding for the fibroblast growth receptor 3 (FGFR3) located on chromosome 4p16.3. The type of receptor mutation is different from the FGFR mutation in achondroplasia. Inheritance is thought to be sporadic.

Plain films are usually done postmortem, if done at all. Features include:

  • narrow chest

  • short horizontal ribs

  • small scapulae

  • platyspondyly: flattening of vertebral bodies

  • normal trunk length

It may be difficult to accurately diagnose before the 3rd trimester (~22 weeks) 4. Before that time it can be included in the differential if there is a short femur length measurement.  

Sonographically-detectable features may include:

  • relatively narrow thoracic cavity 4

  • short, thick, bowed tubular bones, especially of lower extremities 4

  • thickened soft tissues of extremities 4

  • comparatively large head with frontal bossing 

  • a cloverleaf skull appearance may also be seen: type II (see case 3)

The condition is uniformly fatal within a few hours of birth either from respiratory failure or from brainstem compression from a narrow foramen magnum.

The term thanatophoric derives from the Greek words "thanatos" (θάνατος) meaning "death" 2 and "phoros" meaning "bearing/carrying/bringing". 

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Cases and figures

  • Case 1
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  • Case 2
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  • Case 3: type II
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  • Case 4
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  •  Case 5
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  • Case 6
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  • Case 7
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  • Case 8
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