What are the genetic changes related to Legg-Calv-Perthes disease ?
Legg-Calv-Perthes disease is usually not caused by genetic factors. The cause in these cases is unknown. In a small percentage of cases, mutations in the COL2A1 gene cause the bone abnormalities characteristic of Legg-Calv-Perthes disease. The COL2A1 gene provides instructions for making a protein that forms type II collagen. This type of collagen is found mostly in cartilage, a tough but flexible tissue that makes up much of the skeleton during early development. Most cartilage is later converted to bone, except for the cartilage that continues to cover and protect the ends of bones and is present in the nose and external ears. Type II collagen is essential for the normal development of bones and other connective tissues that form the body's supportive framework.  COL2A1 gene mutations involved in Legg-Calv-Perthes disease lead to production of an altered protein; collagen that contains this protein may be less stable than normal. Researchers speculate that the breakdown of bone characteristic of Legg-Calv-Perthes disease is caused by impaired blood flow to the femoral head, which leads to death of the bone tissue (osteonecrosis); however it is unclear how abnormal type II collagen is involved in this process or why the hips are specifically affected.