Achondrogenesis type II (ACG2) is characterized by severe micromelic dwarfism with small chest and prominent abdomen, incomplete ossification of the vertebral bodies, and disorganization of the costochondral junction. ACG2 is an autosomal dominant trait occurring mostly as new mutations. However, somatic and germline mosaicism have been reported (summary by Comstock et al., 2010).

Spondylometaphyseal dysplasia, Schmidt type has characteristics of short stature, myopia, small pelvis, progressive kyphoscoliosis, wrist deformity, severe genu valgum, short long bones, and severe metaphyseal dysplasia with moderate spinal changes and minimal changes in the hands and feet. This condition has been reported in five members of an Algerian family and one Polish boy. Autosomal dominant inheritance has been suggested, but the causative gene has not yet been identified.