Metatropic dysplasia (MTD) is a rare spondyloepimetaphyseal dysplasia characterized by a long trunk and short limbs in infancy followed by severe and progressive kyphoscoliosis causing a reversal in proportions during childhood (short trunk and long limbs) and a final short stature in adulthood.

Abnormally increased movement at the junction between the first cervical (atlas) and the second cervical (axis) vertebrae as a result of either a bony or ligamentous anomaly.