Diseases

Glass bone disease - causes, symptoms and therapy

Glass bone disease - causes, symptoms and therapy


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Glass bones - Osteogenesis imperfecta

The osteogenesis imperfecta means "imperfect bone formation" and is colloquially referred to as glass bone disease. This rare hereditary disease is based on certain genetic defects that affect the collagen balance. This leads to disorders in connective tissue and bone metabolism in those affected. The result of deformable and easily fragile cooking is the main symptom, which is behind the pictorial concept of glass bones. The treatment is based exclusively on symptomatic therapeutic methods in order to prevent bone fractures as much as possible and to provide them with the best possible care.

A brief overview

The following overview shows the most important facts about the topic of the rare inherited disease Osteogenesis imperfecta. Detailed information on the complex clinical picture can be found in the following article.

  • definition: The osteogenesis imperfecta (glass bone, glass bone disease) denotes an inherited collagen malformation that primarily causes a connective tissue disorder. In particular, the disease leads to imperfect bone formation, which manifests itself in the key symptoms of increased bone fractures and bone deformations.
  • Symptoms: In addition to the abnormally high susceptibility to spontaneous fractures and bone deformation, the disease causes a large number of other complex symptoms. Typical symptoms include muscle weakness and blue sclera. The severity of the disease ranges from very light forms to lethal manifestations.
  • causes: Triggers are various gene mutations that are responsible for disorders in collagen formation (collagen type 1). Collagen is the main component of connective tissue and an important building block for bones and other structures and tissues. Therefore, there are not only disorders in the entire musculoskeletal system but also in many other areas of the body.
  • diagnosis: In addition to a thorough medical history and clinical examination, X-ray examinations are primarily used to make the diagnosis. If necessary, the diagnosis can be confirmed by genetic evidence. In prenatal cases, more severe forms of the disease can often be identified using prenatal ultrasound.
  • treatment: The conventional medical treatment of the symptoms is mostly based on relatively new drugs (biophosphonates), orthopedic measures and continuous physiotherapy. The therapeutic options are still in development. In addition, general health promotion measures and osteopathic treatment can be consulted.
  • Current state of research: Current research into the causes of diseases (molecular genetics) and therapeutic options are intended to expand knowledge about this rare inherited disease and to ensure the best possible care for those affected.

Definition

The medical term osteogenesis imperfecta (general abbreviation: OI) is derived from the Greek and refers to imperfect bone formation. In general parlance, however, the terms glass bone or glass bone disease are mostly used, which refer to the main symptom of increased bone fractures. First and foremost, the clinical picture is a rare hereditary connective tissue disorder that occurs due to various genetic defects and leads to collagen malformation (type I collagen). Osteogenesis imperfecta occurs in approximately one in 20,000 births.

Classification and clinical features

A variety of different genetic defects and the resulting disorders in the collagen composition lead to this disease. Because of this, there are also different symptoms in those affected and the clinical picture shows a large variability in severity and in the course of the disease.

In 1979, a four-type classification was introduced for the first time, which subdivided different types of disease and their clinical peculiarities. The description of types I to IV goes back to the Australian physician David Sillence. In these four forms, mutations of the genes coding for type 1 collagen (COL1A1 or COL1A2) occur, which in Europe are more than 80 percent the cause of the disease.

Continually new genetic and clinical knowledge has led to an expansion of this division. Eleven types are currently described, which also take other genes and mutation forms into account. However, only types I to VI are used as largely as possible. To date, not all forms can be assigned, because the large number of causative genes makes clear classification difficult. The extended classification is therefore still under discussion and there is still a need to clarify unclassified forms of the disease.

The common type I with a slight course is also known as the Osteogenesis imperfecta tarda or type Lobstein and the most serious, lethal type II is known as the Osteogenesis imperfecta congenita or type Vrolik.

Symptoms

Despite the high variability in the symptoms that occur, the abnormally high inherent susceptibility of the bones to fractures (osteopsathyrosis) is in the foreground in almost all illnesses. The fractures occur due to a reduced bone mass and a lack of stability and elasticity without adequate trauma (spontaneous fractures).

In addition, there are (pronounced) skeletal deformities, in particular the long bones in the extremities and the spine (scoliosis, kyphosis) and short stature.

In addition to these main symptoms, depending on the severity, the following additional symptoms may occur:

  • Muscle weakness, decreased muscle tension (hypotension),
  • expandable joints and ligaments,
  • independent bone islands (switch bones) on the skull cap,
  • blue sclera (leather skins of the eyes),
  • Deafness,
  • Myopia,
  • Heart problems,
  • Pulmonary disorders (deformation of the chest),
  • Discoloration and brittleness of the teeth (dentinogenesis imperfecta),
  • Tendency to hematoma,
  • soft, translucent skin,
  • triangular face shape with a broad forehead and protruding ears.

Course of the disease

The many possible complaints and degrees of severity cause individually very different disease courses. With moderate and severe course of the disease, fractures and deformities on the extremities and spine already occur during the first months of life. The growth phases up to adolescence are particularly critical, during which fractures occur again and again with very little force.

But prenatal fractures, deformities and other abnormalities can also occur on the bones. In the most severe form (type II), the disease is either fatal in prenatal life or is fatal in the first few months of life. Other serious forms can, due to the frequency of fractures and possible bone bends, prevent those affected from standing and walking.

If, on the other hand, there is a mild form of the disease (type I), sufferers usually experience only a few fractures in childhood and adolescence without further restrictions. Many diseases have in common that the fracture rate drops significantly after the end of puberty.

In principle, there is no reduced life expectancy with the viable forms and with appropriate therapy applications.

Causes

The rare hereditary disease is predominantly inherited in an autosomal dominant manner. An inheritance takes place regardless of gender and the disease can already manifest itself if the corresponding gene defect is only on one of the 22 autosome pairs (body chromosomes). If neither of the two parents has transmitted the disease, a spontaneous mutation can also be the trigger.

The most common genetic mutations that are associated with this disease lead to quantitative or qualitative disorders in collagen formation. Most often, type I collagen is affected, which is often equated to the general term collagen. Collagens are the most common fiber-forming proteins (structural proteins, fiber proteins) with binding and supporting functions in different parts of the human body. Type I collagen is the main component of connective tissue. It is also an important building block for bones, cartilage, tendons, ligaments, teeth, and skin as well as the conjunctiva (conjunctiva). The disease therefore affects not only the skeletal system, but the entire musculoskeletal system and all other structures that contain a certain amount of type 1 collagen.

Despite the clear cause of the gene mutation, even with the latest methods it is not always genetically detectable.

Diagnosis

The first point of reference when making a diagnosis is provided by the patient survey (anamnesis), in which, in addition to the typical symptoms, a familial occurrence of an osteogenesis imperfecta is clarified. In addition, physical examinations, X-rays and laboratory examinations are used to rule out other possible skeletal diseases that occur in childhood (e.g. rickets and hypochondroplasia). The exclusion of causal trauma for existing bone fractures is of particular importance. This can also be relevant in cases of suspected child abuse.

An increased transparency of the bones can be seen in the x-ray. The structures appear glass-like because there is not enough shadow-giving bone substance. The outer layer is usually thinned like a line. Callus formation is often visible. This is scar tissue, which widens and deforms the bone at the fracture point.

In addition, a bone density measurement can provide information about the disease, because the bone density is significantly reduced in those affected. A reliable description of the bone structure and the muscle-bone interaction is possible using computed tomography, but this is not applicable to every person affected (minimum body size).

If symptoms appear on other structures and organs in addition to the symptoms on the skeleton, these are also examined clinically.

A genetic examination, which looks for causative gene mutations, provides a confirmation and extension of the diagnosis. It is not always possible to prove the disease and the underlying genetic defect, but a possible identification serves not only to find the diagnosis but also to further classify and clarify the inheritance risk. If genetic evidence has been provided, this does not mean at the same time that a reliable statement about the individual expression or viability can also be made. Before delivery, a cytogenetic examination is carried out with the help of a mother cake puncture (chorionic villus).

In general, the more serious forms of vitreous bone disease in the womb can already be detected during prenatal ultrasound. Typical findings include shortened and deformed limb bones, rib fractures and occasionally callus formation.

Treatment

So far, there are no options for combating the causes or curing this hereditary disease. The symptomatic treatment is based on the three pillars of medical treatment, orthopedic treatment and physiotherapy, which are recognized by conventional medicine.

Medication

In recent years, bisphosphonates administered intravenously, especially in medium and severe cases, have proven to be a successful treatment option. The medications (for example neridronate and pamidronate) cause an increase in bone mass and an increase in bone strength. As a result, broken bones and improved mobility are less common. The various bisphosphonates are not yet approved for the therapy of osteogenesis imperfecta, which is why their use must be clarified individually. A so-called "individual healing attempt" with these medicinal products can only be carried out with the express consent of those affected. Close monitoring of the effectiveness and potential side effects is essential.

Contrary to some treatment concepts of other bone diseases, an addition of vitamin D and calcium does not make sense beyond the general recommendations.

Orthopedic treatment

The most common symptoms of broken bones and deformities usually require intensive orthopedic treatment. The main goal of this form of therapy is to maintain or restore the functionality and resilience of the skeletal system. Conservative measures for broken limb bones include special winding and positioning techniques, especially for very young children. Furthermore, orthoses (e.g. splints) and plaster casts are used.

In more complicated cases, however, surgical interventions are necessary to avoid fractures and malpositions, or to correct and heal them. In operations in childhood and adolescence, taking the growth phases into account is of particular importance. If possible, this requires the use of a telescopic nail system (Bailey or Fassier-Duval nail). Here, often after several targeted bone cuts (osteotomies), two nested nail parts are inserted into the inside of the bone. The bone parts are connected again and during growth these nails slide apart together with the bone. In this way, the bones can be stabilized over a long period of time.

In very young children, the bones may not yet have enough space for a telescopic nail. If this is the case, other aids are used, which may then have to be removed or replaced at a later time.

Physiotherapy treatment

In order to prevent the risk of malposition, incorrect posture and skeletal changes, individually tailored physiotherapy is of great importance. Targeted physiotherapy is also a central component of the therapeutic measures for rehabilitation after bone fractures. The primary goal is to improve or increase mobility and to strengthen the muscles. Every person affected should receive regular and continuous physiotherapy treatment and support the other treatment measures.

If other areas of the body or organs are affected, such as the lungs or the heart, additional forms of therapy may be necessary.

Naturopathic treatment

The conventional medical procedures for the treatment of an osteogenesis imperfecta can be supported by general, health-promoting measures. As much exercise as possible, sport (swimming) and not using cigarettes and alcohol have a positive effect.

In addition to the physiotherapeutic treatment, measures from the field of osteopathy can also help to alleviate the symptoms. A visit to the naturopath can also be helpful.

Current state of research

Although the disease has been known for a long time, the complex genetic basis and widely varying forms of disease require intensive research, especially in the area of ​​the causes of the disease and the individual treatment options.

In 2017, the consensus paper published by the "Monthly Pediatric Medicine" mentions studies and research approaches in the area of ​​the use of biophosphonates and other medications, such as the effects of parathyroid hormone as a bone-building-stimulating medication in adults. International studies are also being carried out in the field of gene and cell therapy as a treatment option.

Only recently has the change in the collagen been deciphered, which is most likely responsible for the reduced resistance of the bones in the case of glass bone disease.

Since it is a rare clinical picture, there are no defined guidelines for the care of those affected. German specialist doctors, who have been treating children and adolescents with osteogenesis imperfecta for a long time, have summarized the current status of the clinical picture in the advanced training magazine "Pediatrics up close". (tf, cs)

Author and source information

This text corresponds to the specifications of the medical literature, medical guidelines and current studies and has been checked by medical doctors.

Dr. rer. nat. Corinna Schultheis

Swell:

  • German Society for Osteogenesis imperfecta (Glass Bones) Affected e.V .: Information for Affected (accessed: 03.07.2019), oi-gesellschaft.de
  • Merck & Co., Inc .: Osteogenesis imperfecta (accessed: July 3, 2019), msdmanuals.com
  • Stanford Health Care: Osteogenesis Imperfecta (accessed: 03.07.2019), stanfordhealthcare.org
  • UpToDate, Inc .: Osteogenesis imperfecta: Management and prognosis (accessed: 03.07.2019), uptodate.com
  • Brittle Bone Society: What is OI? (Accessed: 03.07.2019), brittlebone.org
  • GFMK GmbH & Co. KG: Osteogenesis imperfecta - information for affected persons and their relatives (access: 03.07.2019), osteogenesis-imperfecta.net

ICD codes for this disease: Q78ICD codes are internationally valid encodings for medical diagnoses. You can find e.g. in doctor's letters or on disability certificates.


Video: OSTEOGENESIS IMPERFECTA OI, Causes, Signs and Symptoms, Diagnosis and Treatment. (September 2022).


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