Osteogenesis imperfecta

Osteogenesis imperfecta is a genetic disease that causes weak bones, often resulting in frequent bone breaks, sometimes even without apparent cause. Because of this, it is also known as brittle bone disease. Osteogenesis imperfecta is caused by failures in the production of collagen, a fundamental protein of connective tissue that supports the body.

There are at least 8 types of osteogenesis imperfecta, each with varying severity of the associated symptoms. The first four types are the most frequent. Type I is the most moderate, and type II is the most severe form of the disease. The rest are intermediate forms between type I and II.

Symptoms of osteogenesis imperfecta: The milder and more moderate forms of the disease are characterized by multiple fractures usually due to small blows, and whose number usually decreases over time, being more infrequent in adulthood. Other symptoms include hearing loss earlier than normal and sometimes the presence of a bluish coloration of the white part of the eye.

In the most severe types of osteogenesis imperfecta, fractures often occur without apparent cause, and symptoms may include breathing problems, short stature, scoliosis, hearing loss, and even problems in dental development. More severe symptoms of this disease may also include problems in the development of the lungs that cause lifelong breathing difficulties.

While there is no cure for this disease, there are treatments and therapies that can reduce pain and alleviate some of the symptoms of osteogenesis imperfecta. Bisphosphonates are medications that have been shown to help in treating symptoms associated with this disorder, as they reduce pain and strengthen bones. Swimming is also highly recommended, as it is a low-impact exercise and helps strengthen the muscles. In the most severe cases, surgery can be used to strengthen the bones with prostheses.

The prognosis of osteogenesis imperfecta depends on the type. People with type I usually have a normal life expectancy, but children with type II usually do not reach the first year of life. In intermediate types, life expectancy is usually shorter because of the intensity of their symptoms.

Approximately 90% of cases of osteogenesis imperfecta are caused by errors in the COL1A1 and COL1A2 genes, associated with type I collagen, which is present in bones and connective tissues and provides structure and strength to the body. Type I is caused by mutations in the COL1A1 gene, while types II, III, and IV can result from mutations in either gene.

There are two genes in which mutations are responsible for the rarest cases of the disease: CRTAP (type VII) and LEPRE1 (type VIII).

In types V and VI, the associated mutations are not known.

Osteogenesis imperfecta is a rare disease whose incidence varies between 1 in 10,000-15,000 people. It occurs in all races equally and is independent of gender.

In Spain, it is estimated that there are approximately 2,700 individuals affected by osteogenesis imperfecta, with milder forms of the disease often not being diagnosed.

Most cases follow an autosomal dominant pattern of inheritance, which means that a single copy of the defective gene is sufficient to cause the disease. Most children with the most severe types of this disease (II and III) are carriers of the so-called sporadic mutations, which occur spontaneously in individuals with no family history of the disorder.

In the rarest cases of the disease (types V, VI, VII, and VIII), the pattern of inheritance is usually autosomal recessive, meaning that both copies of the gene must be altered for the disease to appear. Some cases of type III may also be associated with this type of inheritance.

AHUCE – National Brittle Bones Association

AMOI – Madrid Association of Osteogenesis Imperfecta

osteogenesis.info – Page with information about osteogenesis imperfecta

OI Foundation – American Osteogenesis Imperfecta Foundation