ARCN1 and osteogenesis imperfecta: Figure 3 shows the histological examination in our patient compared with an age matched control and with histology from a fetus with a KDELR2 mutation with typical histology from a severe osteogenesis imperfecta phenotype. In our ARCN1-patient, the growth plate showed a relatively thin hypertrophic zone, and the proliferative zone had a normal width.