Most common nonlethal skeletal dysplasia

Long bones

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  Short limbs with normal ossification, no fractures

  
  
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  Rhizomelia: Proximal long bones (femur, humerus) more affected than distal long bones

  
  
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  Upper extremities more severely affected than lower

  
  
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  Femurs may show mild bowing but no angulation

  
  
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  Shortening often not present until late 2nd and 3rd trimester

Head and face

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  Progressive macrocephaly with frontal bossing

  
  
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  Depressed nasal bridge with upturned nasal tip

Chest normal to mildly bell-shaped

Spine has prominent thoracolumbar kyphosis

Trident-shaped hands with short fingers

Autosomal dominant inheritance

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  If one parent has achondroplasia, fetus has 50% chance of being affected

Over 80% of cases new mutations, so neither parent may be affected

In any case of suspected skeletal dysplasia, pay particular attention to appearance and ossification of long bones

Profile views and 3D images of face are very important to look for classic features

Obtain sagittal views of spine to look for abnormal outward curvature (kyphosis)

Need to follow-up at-risk fetuses (i.e., parent with achondroplasia)

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  Limb shortening and classic facial features may not be apparent at time of routine anatomy scan