Brittle Bone Disease is a genetic disorder, and as the name suggests, it is a bone condition in which the patient's bones become brittle or easily breakable. Although in most cases this condition is inherited, there are cases where it could be an independent mutation as well. There are up to eight different categories of brittle bone disease, each with its own unique symptoms.
What is Brittle Bone Disease?
In medical terms, this condition is known as Osteogenesis Imperfecta (OI) or sometimes also called "Lobstein syndrome". A person with this disease is born with defective collagen or insufficient amounts of collagen (usually Type-I collagen), which is a crucial protein in connective tissues. In some cases, (see categories below) collagen might be both insufficient and defective, in which case, death occurs within the first year of birth itself. To understand the symptoms and how they differ according to the type of OI that a person has, continue reading the following HealthHearty article.
Symptoms and its Categories
There are eight different categories with their own unique symptoms.
Type IType I OI is caused by disorders in the genes COL1A1 and COL1A2. In this type, the symptoms include bones that are easily fractured, slight curvature in the spine, loose joints, poor muscle tone, blue gray coloration of the sclera or the white part of the eye which is due to insufficient Type I Collagen. The eyes are also slightly protruded, and in some cases early loss of hearing occurs. This can be further divided into Type IA and Type IB on the basis of the presence of opalescent teeth which is seen in Type IB but absent in Type IA.
Type IIIn Type II OI, the collagen produced is neither sufficient nor perfect. It is caused by an anomaly in the COL1A1, COL1A2 and CRTAP genes. Most cases with this type, die within a year of birth due to conditions such as respiratory failure due to underdeveloped lungs or intracerebral hemorrhaging. Bones are highly deformed. It can be further classified on the basis of lengths of the long bones and ribs.
Type IIIThere is a sufficient amount of collagen but not of the required quality, and this results from disorders in the COL1A1 and COL1A2 genes. The symptoms include bones that easily fracture, at times even before birth, severe deformation of bones, chances of respiratory problems, loose joints, and discoloration of the sclera. A person with this type of OI has a short stature with a barrel-like rib cage, poor muscle tone, especially in the arms and legs and spinal curvature. Hearing loss is also possible early in life.
Type IVThis type of OI is very similar to Type III and is caused by the same genes, COL1A1 and COL1A2. In this form, however, the bone deformities are not as severe as in Type III. It is also classified into two types (IVA and IVB) on the basis of the presence of imperfect teeth.
Type VIt is characterized by "mesh-like" appearance of the bones. It leads to calcification between the joints of the forearm making it difficult to fully move the wrist. Also, a large amount of hyperplasic callus or repair tissue is seen at fracture sites. The cause of Type V is unknown, but what is known is that it is inherited.
Type VIIts unique symptom is that the bones look like fish scales. The rest of the brittle bone disease symptoms are similar to Type IV OI. The cause for type VI is also unknown.
Type VIIThis is a recently discovered form of OI. It was discovered in 2005, and seems to be limited to the native people of Quebec. It is caused when there is a low supply of CRTAP gene, thus leading to mild bone fragility. It is a recessive form of OI and the parents could be carriers of this disease even though they do not exhibit its symptoms.
Type VIIIThis is caused by mutation in the LEPRE1 gene and is characterized by slow growth. Bones are deformed and they may fracture even before birth.
Type ILife expectancy in Type I is slightly less than that of a normal human being because of the increased risk of fractures and other such complications. There is also a chance of Basilar Invagination when the C2 vertebrae move upward, narrowing the opening in the skull where the spinal cord enters the brain.
Type IILife expectancy is very low and most Type II cases die within a year of being born. It is one of the most fatal types of OI.
Type IIIIn Type III, the life expectancy is better than in most other cases, as the patient first shows mild symptoms, and slowly develops other brittle bone disease symptoms as years go by. The patient could even have a normal life span but would be physically handicapped.
Type IVBones are easily fractured before puberty, and there will be other disabilities but the life span is a little less than normal.
Type V, VI and VIIIHere too, the life span is shortened. The affected individual has a life span that is lesser than that of normal individuals.
Type VIIThis is a recessive Type of OI and thus the person lives a normal life, without any symptoms except for mild bone fragility, but could transfer the genes for OI to their children.
Treatment for the symptoms of brittle bone disease, is done by using different methods that include: surgery to insert metal rods to support bones, physiotherapy to increase muscle strength, use of physical aids for support and biophosphonate therapy to improve bone density. Research continues in order to better understand this disease, and other similar genetic disorders. The human genome is being mapped and each gene and its functions, analyzed. There is still no cure for brittle bone disease but with the advancements in the field of human genetics and biotechnology, great things are expected.
Disclaimer: The information provided in this article is solely for educating the reader. It is not intended to be a substitute for the advice of a medical expert.