Osteogenesis imperfecta: from phenotype to genotype and back again.

The presumption that identification of the collagen gene mutations in OI would completely explain the phenotype is unjustified. Full understanding of this fragile bone syndrome will depend on the intelligent interpretation of both the biochemical abnormalities and the clinical features. Between these extremes there is a whole unexplored area of cell biology. To make further progress it seems that we shall have to pay as much attention to the phenotype as to the genotype.