Osteopetrosis can cause a number of serious, potentially life-threatening problems throughout the body.
According to the US’s National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), it is triggered by an imbalance in the formation and breakdown of bone.
This causes the bone to become overly dense, but also weak and at risk of breaking easily.
Unlike the similar-sounding osteoporosis – where bones become brittle and fragile from loss of tissue – people are born with osteopetrosis.
Bones that are too dense can interfere with important tissues and structures.
For example, compression of nerves in the skull can lead to vision loss, hearing loss, or paralysis of facial muscles.
The NIAMS warn that it can also trigger crowding of the bone marrow, which may lead to low levels of cells needed to fight infection, carry oxygen to the body’s cells, or control bleeding.
In some cases this case can prove deadly.
There are two main types of osteopetrosis – malignant infantile and adult.
The former is apparent shortly after birth and can reduce life expectancy.
In contrast, the adult form may not be diagnosed for decades.
According to the NIAMS, it is caused by defects in one or more genes involved in the formation, development, and function of cells called osteoclasts.
These cells break down bone tissue during a standard process called bone remodelling, where old bone is removed and new bone is created to replace it.
The most common symptoms of osteopetrosis are bone fractures, low blood cell levels, impaired vision and hearing, and dental problems related to infection.
However, their severity varies from person to person.
The condition can usually be posted on x-rays, where bones appear unusually dense or chalky white.