metatropic dwarfism

[mĕt′ə-trŏpĭk, -trōpĭk]
n.
  1. A congenital skeletal dysplasia in which the development of dwarfism changes with time; at birth the trunk lengthens relative to the limbs but later it begins to shorten.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.