A team of researchers has identified a new genetic mutation responsible for osteogenesis imperfecta (OI), a condition that makes bones much more likely to break, according to a study published today in the journal Cell.

Victims may experience just a few fractures in a lifetime or several hundred beginning before birth. The number of Americans affected is unknown, but estimates range from 20,000 to 50,000.

While the study is an important early step in the search for a cure, its immediate effect may be to exonerate an expanded group of parents whose children frequently appear in emergency rooms with unexplained fractures, and who may be accused of child abuse.

The study was led by Brendan Lee, M.D., Ph.D., associate professor of Molecular and Human Genetics at the Baylor College of Medicine. Brendan Boyce, M.D. professor of Pathology at the University of Rochester Medical Center, added expertise to the large, international research team in the analysis of skeletal defects caused by lack of effective function in the newly discovered gene.

Previously, OI was known only as a genetic disorder in the formation of collagen fibers, the protein framework of which bone and cartilage are built. People with OI were known to have a faulty gene that instructed their bodies to make either too little or weak collagen because of defects or mutations in one of the collagen genes, of which there are more than 20.

The current study found a new gene, that when mutated, reduces the ability of a protein involved in collagen formation, called CRTAP (cartilage-associated protein), to guide collagen production as it forms the proper framework of bone.