Osteopetrosis

Osteopetrosis, literally "stone bone", also known as marble bone disease, is an extremely rare inherited disorder whereby the bones harden, becoming denser. Despite this excess bone formation, people with osteopetrosis tend to have bones that are more brittle than normal. Osteopetrosis is caused by mutations that interfere with the acidification of the osteoclast resorption pit, leading defective to bone resorption by osteoclasts, as an acidic environment is needed to dissociate calcium hydroxyapatite from the bone matrix. The only durable treatment is bone marrow transplant.