On histopathology of the growth plate, there is a quantitative decrease in endochondral ossification. Precise prenatal ultrasonographic diagnosis is possible in the third trimester, and sometimes even in the second. Hypochondroplasia is a relatively common, milder form of achondroplasia, which varies within and between families and lacks the neurological complications often seen in achondroplasia of this group. An accurate prenatal ultrasonographic diagnosis is rare. There are milder changes on histology of the growth plate.
Thanatophoric dysplasia is the lethal and most severe dysplasia.
On histopathology of the growth plate, there is disruption of endochondral ossification. 3 du facteur de croissance du fibroblaste du chromosome 4p.