Lethal skeletal dysplasia

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  Thanatophoric is Greek for death bearing

Divided into 2 subtypes based on morphologic findings

Features seen in both TD1 and TD2

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  Micromelia : All bones extremely short

  
  
  
  
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    Can be seen as early as 14 weeks

    
    
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    Becomes worse with advancing gestation

  
  
  
  
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  Bones normally ossified

  
  
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  Long bone bowing but no fractures

  
  
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  Chest small with short, straight ribs

  
  
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  Vertebral bodies flattened (platyspondyly) with exaggerated lumbar lordosis

  
  
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  Most have severe polyhydramnios by late 2nd trimester

TD type 1

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  Femur more severely shortened and bowed

  
  
  
  
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    Telephone receiver appearance

  
  
  
  
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  Macrocephalic but relatively normal-shaped skull

TD type 2

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  Distinctive cloverleaf-shaped skull (kleeblattschädel)

Most important task in approaching skeletal dysplasia determining lethal vs. nonlethal

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  Lethal findings generally include micromelia and very small chest

Obtain coronal and sagittal views of chest and abdomen

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  Abdomen will appear protuberant compared to chest

Measure chest circumference and cardiothoracic ratio on 4-chamber view of heart

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  Heart may appear large but appearance actually because chest small

Look carefully for more specific features

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  TD type 1: Very curved femur (telephone receiver)

  
  
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  TD type 2: Cloverleaf-shaped skull