Such observation has been reported in patients with some other osteochondrodysplasias, including spondylometaphyseal dysplasia with “corner fractures” caused by mutations in the fibronectin gene and metaphyseal anadysplasia caused by mutations in metalloproteinases.(48, 49, 50, 51) Interestingly, incomplete penetrance and variable expression among patients with identical mutations is a common feature in ribosomopathies,(8) but the underlying mechanisms still remain largely unknown. The gene discussed is FN1; the disease is spondylometaphyseal dysplasia.