Osteogenesis Imperfecta with a gross deletion including the COL1A1 gene, induced by Alu-driven microhomology-mediated end joining.

Osteogenesis Imperfecta (OI) is a rare hereditary brittle bone disorder typically caused by COL1A1 and COL1A2 variants impairing type I collagen. However, gross deletions involving COL1A1 are uncommon. Here, we report a family with type I OI harboring a 101-kbp deletion encompassing COL1A1, identified through whole genome analysis. Affected individuals presented mild phenotypes. Breakpoint analysis revealed a 5-bp microhomology-mediated end joining involving an Alu element. This report expands the understanding of genetic mechanisms underlying OI.