What is a characteristic feature of Achondrogenesis?

Achondrogenesis is a severe skeletal dysplasia characterized primarily by significantly underdeveloped bones and cartilage. One of the hallmark features of this condition is severe micromelia, which refers to disproportionately short limbs. This results from a failure of normal endochondral bone formation and leads to pronounced shortness of stature at birth.

In contrast to the other options, advanced skull ossification would not be characteristic of achondrogenesis; typically, there is a reduction in ossification. Normal thoracic circumference is also not consistent with this condition, as babies with achondrogenesis often have a small thoracic cavity, which can lead to respiratory complications. Additionally, extended long bones are not seen in achondrogenesis because the condition results in shortened and deformed long bones rather than elongated ones. Thus, the identification of severe micromelia is crucial for recognizing achondrogenesis, making it the correct answer in this context.