5 Rare Bone Disorders You May Never Have Heard Of


Depending on who you ask, most people would say that we have 206 bones. After all, that's what we’ve been taught in school and it is a good approximation. Did you know that in our hands and feet we have tiny bones called sesamoids which are often not included in the count! Some people also have an extra pair of ribs, which similarly is left out of that 206 bone count. So when someone asks you how many bones an adult human has in their body, the correct answer would be “more than 206, depending on how you count them…”.

Regardless of exactly how many you have, several common and rare diseases can affect your bones in various ways. Since your bones and skeleton form the literal foundation for the rest of your body, problems with it can lead to some serious difficulties. Let's have a look at some of the lesser-known bone diseases and disorders:

Candle wax bones

Melorheostosis is a relatively rare bone disease in which some bones of the body grow additional external layers. This usually presents as bulging growths (like dripping candle wax) on x-ray scans. This excess bone layer disease normally stays confined to one area of the body. Another oddity of Melorheostosis is the non-symmetrical way it acts, affecting mostly either the left or right side of the bone that it occurs on.

Unfortunately, the exact cause of the disease is unknown, with scientists’ best guess being that some mutation occurs in the area and is passed on through normal cell division. Treatment is not fixed but may include things like physiotherapy, symptom reduction, medication for adjusting bone creation and pain management medication.

Extra thick forehead bone

Hyperostosis Frontalis Interna is a disease where the internal part of the front bone in your skull grows thicker than normal. While it’s rare in men it’s much more or less common in women occurring in over 12% of the general female population. Thankfully for something that affects so many people it doesn’t come with too many harmful side-effects, most people affected usually have no symptoms. You might be one of those people and have this condition without even knowing it!

Those who do have symptoms though might experience things like headaches or in extreme cases memory loss. Treatments usually are directed at the symptoms rather than cure.

Dwarfism causing disorder  

Dwarfism is a condition in which an adult has an uncommonly short stature, and Achondroplasia is one of the leading causes of dwarfism in humans. When we’re still in our mother’s womb, our bones are in the form of cartilage. These are supposed to eventually turn into bone, but with those who have achondroplasia a lot of the cartilage (especially in the arms and legs), this change does not occur. This in turn leads to arms and legs remaining short.

The cause of this disease is well known, with the culprit being a mutation in the FGR3 gene. This gene is involved with the growth and maintenance of bones, and when it gets mutated it interferes with normal skeletal development.

Brittle Bones

This group of bone disease, called Osteogenesis Imperfecta, leads to low density and a higher risk of bone fracture. It is connective tissue disease that occurs due to genes that are supposed to produce collagen getting mutated. Collagen is a protein that is essential for the structural building of bones, tendons and skin. With collagen creation (and maintenance) being messed up by this mutation, bones aren’t able to grow strong and repair themselves properly.

Some other effects are short stature, spinal bones being curved, poor muscle development, and oddly enough a blue tiny in the white parts of the eyes (veins under the eyes can be seen due to the skin thinning from lack of collagen). Treatments revolve around bone development medication, physical therapy as well as surgery when required.

Fibrodysplasia Ossificans Progressiva

The name itself gives some idea as to what this disease is about. Connective tissues like tendons, cartilage and sometimes muscle turn to bone over a long period of time. Because this bone formation happens outside of the skeleton it leads to restriction of movement in the person, that continues throughout their life. Eventually, they are totally unable to move, as more and more connective tissue and skeletal muscles turn into bone.

The disease is caused by a genetic mutation and is inherited. Starting in childhood in the neck and shoulders, moving down the body but not at a fixed rate. Rapid ossification (turning into bone) occurs in periods after an injury to bones or viral infections, where the inflammation lasts for weeks or months. Treatments are very limited and even surgery might lead to new painful bone development. The exact treatment is up to the patient's doctor.

If all this sounds scary, the one good thing about Fibrodysplasia Ossificans Progressiva is that it is very rare, affecting only one or two people out of a million.


While there's nothing you can do to stop these diseases, you can still take care of your body and consequently your bones. These bone diseases are interesting but we can all be glad we don't have them, hopefully giving us a renewed gratitude for our health.  For more information you always talk to a doctor online on DocsApp.