OI is caused by defects in or related to a protein called type 1 collagen. Collagen is an essential building block of the body. The body uses type 1 collagen to make bones strong and to build tendons, ligaments, teeth, and the whites of the eyes.
Certain gene changes, or mutations, cause the collagen defects. Mutations in several genes can lead to OI. About 80%–90% of OI cases are caused by autosomal dominant mutations in the type 1 collagen genes, COL1A1 and COL1A2. Mutations in one or the other of these genes cause the body to make either abnormally formed collagen or too little collagen. Mutations in these genes cause OI Types I through IV.
The remaining cases of OI (types VI–XI) are caused by autosomal recessive mutations in any of six genes (SERPINF1, CRTAP, LEPRE1, PPIB, SERPINH1, and FKBP10) that code for proteins that help make collagen. These mutations also cause the body to make too little collagen or abnormally formed collagen.
These gene changes are inherited, or passed down from parents to their children; people who have OI are born with it. However, in some cases, the gene mutation is not inherited and occurs after conception.1,2,3,4