Osteopetrosis is an extremely rare inherited disorder whereby the bones harden, becoming denser.

Normally, bone growth is a balance between osteoblasts (cells that create bone tissue) and osteoclasts (cells that destroy bone tissue). Sufferers of osteopetrosis have a deficiency of osteoclasts, meaning too much bone is being created. Despite this excess bone formation, people with osteopetrosis tend to have bones that are more brittle than normal. Mild osteopetrosis may cause no symptoms, and present no problems. However, serious forms can result in stunted growth, deformity, increased likelihood of fractures, and anaemia. It can also result in blindness, facial paralysis, and deafness, due to the increased pressure put on the nerves by the extra bone.

There is no cure, although bone marrow transplants are being tested. It is believed the healthy marrow will provide the sufferer with cells from which osteoclasts will develop.

See also

• V-ATPase