Our bone and skeletal system is not a rigid structure and is naturally subject to a continuous transformation process. Bone substance is regularly degraded by special cells, the so-called osteoclasts, and in return is rebuilt by the cells known as osteoblasts. Structural damage to the bone, caused by everyday movements and loads, is repaired as quickly as possible by the body’s own cells and the fine structure of the bone is adapted to the respective stresses and strains of the environment.
This gives our skeletal system a distinctive stability and functionality. If disorders occur in the area of the cells that break down and build up bone, the bone system suffers a loss of its strength and resistance: it becomes brittle and unstable. Marble bone disease, also known medically as osteopetrosis or Albers-Schönberg syndrome, is a rare hereditary disease.
It results in a reduced function of the above-mentioned bone-destroying cells, the osteoclasts. The modelling of the bone system is disturbed and a shift of the balance in favour of the bone-building cells takes place. Due to the lack of bone resorption activity, marble bone disease leads to increased accumulation of bone substance in the body. This accumulation has a pathological character, because it causes a disturbance of the bone architecture, i.e. of the bone structure and thus a reduced stability of our skeletal system. The remodelling processes even extend so far that the bone marrow, which fills the inner spaces of the bones and embodies an important part of our blood formation and defence system, is replaced by bone substance.
Causes
The exact cause of the marble bone disease is still unknown. It is based on a malfunction of the bone-destroying cells, which is caused by genetic changes in the genetic material of these cells. Two major forms of marble bone disease are distinguished:
- On the one hand there is the autosomal-dominantly inherited form.
Autosomal dominant describes a form of inheritance in which a defective member on the gene carrier of our body, the chromosome, is sufficient to cause a characteristic feature of marble bone disease. This form usually manifests itself only during the growth spurt at the age of maturation of about 12 to 20 years.
- The autosomal recessive form (here both members of an entire pair of chromosomes must be defective), which already in early childhood at the age of one to two years causes a severe form of marble bone disease, stands out from this. Untreated, the second form has a very poor prognosis and can lead to death in early childhood.