What’s osteogenesis imperfecta?

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Brittle bone disease is a rare genetic disorder that causes bones to break easily due to problems with the production and quality of collagen in the body. Also known as osteogenesis imperfecta (OI) or Lobstein syndrome, there are eight different types of this condition, which vary in severity. While there is no cure for brittle bone disease, the symptoms are often manageable. In addition to the effect it has on the body, OI also often has psychological and social effects and can be mistaken for child abuse in some situations.

Types of OIs

There are eight different types of brittle bone disease, which differ in terms of the specific genetic variation that causes them, how collagen is affected, and what other symptoms occur along with the brittle bone. Type I is the mildest, while types II and VIII are considered the most severe. Types III to VII are all considered deforming, but the collagen of those with types V and VI looks different from those with other types.

Of the eight types, types I through V are caused by autosomal dominant genes, meaning a person would only need to get the abnormal gene that causes the disease from one parent. Types VII and VIII are autosomal recessive, which means both parents must pass on the abnormal gene for the child to develop the condition. It is not clear whether type VI is dominant or recessive.

Symptoms

Symptoms of OI vary by type, but in general, people with the condition are short, tend to have many fractures and bruises, a higher-than-average voice, and brittle teeth. About half of people with OI have hearing problems because the sound-transmitting bones in the inner ears break easily or become deformed. They also tend to overheat easily and can sweat a lot. Many also have blue tinges to the whites of their eyes, although people with type IV do not. Those of type V usually have collagen cells that look like meshes, while those of type VI have collagen that has a fish scale appearance.

Diagnosis

Diagnosing brittle bone disease can be difficult, as not all people have symptoms that are immediately visible. Also, bone density tests and X-rays are unreliable, as the bones of those with OI tend to present as normal unless they’ve been broken many times. A diagnosis can be made by looking at the type of collagen a person’s cells produce or by looking at their genes for the types of mutations that cause collagen abnormalities, but neither is a foolproof method.

Treatment
Brittle bone disease has no cure, so treatment focuses on reducing breakage and strain. In type I and type IV, the bones appear to be more vulnerable to breaking during growth spurts, and breaks occur with even the simplest injuries. Physical therapists can work with children to help them build muscle tone to protect bones. Some patients have surgery to fuse the spine, which can help with posture and reduce curvature, but the bones are often so fragile that this surgery is quite risky. There are no specific medications that are generally used to treat this condition, but some people respond well to osteoporosis medications.
Social and psychological effects
Although the condition is most often inherited, a genetic mutation that does not come from a parent can occur in about 25% of cases. If a child with undiagnosed OI has many unexplained broken bones, health authorities may suspect that the parents were abused. A DNA or collagen test can usually clear up the confusion, and those children with OI who cannot be identified through genetic testing can be accurately diagnosed by a qualified expert in the field through distinctive physical characteristics.

Children with brittle bone disease are often afraid to try new things due to fear of painful breakages and injuries. Often, psychotherapy is used to address this fear, and physical therapists can help children understand the safe limits of the body. Many also develop body image issues as teenagers, which psychotherapy and support groups can also help.

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