What is Osteopetrosis?

Osteopetrosis is a rare genetic condition that affects the way a persons bones develop and change.

What does Osteopetrosis mean?

 The word Osteopetrosis comes from the Greek language. It is made up of two words,

  1. Osteo – which means ‘bone’

    and

  2. Petrosis – which means ‘stone’

So when we put the two words together, we get ‘stone bone’. This is actually another name for Osteopetrosis. Some other common names are:

  • Albers-Schönberg disease

  • Marble bone disease

  • Chalk bones

  • Brittle bones

Osteopetrosis was discovered in 1904 by a German radiologist named ‘Albers Schönberg’. This is where the name above comes from.

So what does Osteopetrosis do?

Osteopetrosis causes bones to become thicker and more dense over time. This means they become tougher but not stronger, it actually makes them weaker! If you think of a piece of chalk, it is something hard and tough, fairly ‘solid’ but very dry – if you snap it, it breaks quite easily, and with very little resistance. This is how bones affected by Osteopetrosis behave.  The dryness and weakness of bones is made worse by a lack of something called ‘bone marrow’.

Bone marrow is a soft jelly like substance inside healthy bones. Inside bone marrow, there are lots of different cells responsible for helping our bodies stay strong and healthy.

As well as blood cells, there are cells called osteoblasts and osteoclasts. If the osteoclasts do not do their job, bones don’t grow, develop or heal properly; this is what causes Osteopetrosis.

In our bodies, bones are constantly being broken down and rebuilt (but not enough that we can feel it happening). Osteoclasts break down and clear away old or damaged bone, whilst osteoblasts build new healthier bone. These two cells should work at the same pace as each other which keeps things balanced. But in Osteopetrosis, the osteoclasts fail to clear old bone tissue, leading to a lack of room for new bone formation. Thus, new bone layers pile on top of the existing damaged bone, resulting in an overall denser bone structure.

The way to remember which way around osteoclasts and osteoblasts work, is that osteoclasts is spelt with a ‘c’ for clearing bone away; and osteoblasts spelt with a ‘b’ for building new bone.

Let’s talk a bit more about bone marrow

Bone marrow is very important when looking at Osteopetrosis. The cells we need for healthy bone development and function are all in our bone marrow. In osteopetrosis, there isn’t enough bone marrow in the bones.

As bones become thicker, they also become dryer due to the lack of bone marrow jelly. Bone marrow sometimes acts as a shock absorber too - so when someone falls, the bone marrow absorbs some of the pressure created by the impact, which decreases the chance of fractures. This is why fractures are much more common in those with Osteopetrosis. Healthy bones will also heal correctly, but Osteopetrosis bones will not; because as we know, the osteoclasts aren’t clearing away the broken bone and the osteoblasts are building new ones.

Fractures in bones affected by Osteopetrosis can cause a few different things.

  • Overly lumpy areas of bone bone created by the imbalance of osteoclasts and osteoblasts

  • Long term fractures which do not heal because there is not enough bone marrow in the body; which means there aren’t enough bone remodeling cells.

These fractures can cause a lot of pain, and sometimes limits the use or movement of that part of the body. Fractures in the spine can affect the spinal cord, so a person can lose movement of their entire body. Other examples include fractures and abnormal ‘lumps’ in the hands, fingers, feet or toes.

A lack of bone marrow can affect the body’s ability to fight germs, make blood, and so much more!

Although everyone is affected differently, here are some of the most common signs and symptoms

·        Stunted growth

·        Bowed legs

·        Prone to fractures

·        Sensory impairment or loss (vision and hearing)

·        Dental abnormalities

·        Prone to infection (weak immune system)

·        Enlarged spleen and/or liver

·        Delayed development (physical and/or mental)

·        Fatigue (Tiredness/Low energy)

·        Anaemia (Low iron/haemoglobin)

·        Macrocephaly (enlarged head)

·        Nerve damage

·        Mobility impairment (difficulties with movement such as walking)

Common symptoms