Achondroplasia

Michael P. D'Alessandro, M.D.
Peer Review Status: Internally Peer Reviewed

Etiology/Pathophysiology:
Disorder of tubular bone growth. Autosomal dominant.

Pathology:
Not applicable

Imaging Findings:
Rhizomelic limb shortening is seen. On plain film see short tubular bones with normal width and shortening of humerus compared to radius and ulna with flared metaphyses. Pelvis has a "champagne glass" appearance with square iliacs bones, broad flat acetabular roofs, and a small sciatic notch. Decreased distance between pedicles in lumbar spine is noted as you descend through it. The pedicles are shortened. Vertebral bodies are normal height but have concave posterior border. There is a large calvarium with prominent frontoparietal and occipital regions with a short skull base and mid face hypoplasia.

DDX:

• Hypochondroplasia (milder)
• Thanatophoric dwarf (more severe in newborn)
• Pseudoachondroplasia (skull is normal and epiphyseal ossification is severely disturbed)

References:
See References Chapter.

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