Osteogenesis Imperfecta (OI), or brittle bone disease, is a genetic disorder affecting the body’s ability to make strong bones. It is caused by a defect in the genes that produce type I collagen, a protein that is a building block for bone. This results in fragile bones that break easily. Life expectancy with OI can vary significantly depending on the specific type of the disorder.
Life Expectancy by OI Type
The prognosis for an individual with OI is tied to the specific classification of the disorder. There are several distinct types, with the most common being Types I through IV, which range from mild to severe. The life expectancy differs substantially across this spectrum, making an accurate diagnosis important for understanding a person’s long-term outlook.
Type I OI is the most common and mildest form of the disorder. Individuals with this type have a normal or near-normal life expectancy and can lead productive lives. While they experience more fractures than the general population, particularly before puberty, these tend to decrease in frequency in adulthood. The underlying collagen structure is normal, but the amount produced is reduced, leading to bone fragility but not severe deformities.
In contrast, Type II OI is the most severe form and is often lethal at or shortly after birth. The genetic mutations in Type II cause profound issues with collagen production, leading to numerous fractures while in the womb. A primary factor in its high mortality rate is severe underdevelopment of the lungs, which causes respiratory failure. Survival beyond the first year of life is rare.
Type III OI is a severe and progressively deforming type, but it is not lethal in infancy. Individuals often have fractures at birth and experience them throughout life, leading to significant bone deformities, a short stature, and the need for a wheelchair. While life expectancy can be shortened due to complications, many people with Type III OI live into their adult years.
Type IV OI is a moderate form of the disorder, falling between Types I and III in severity. People with Type IV experience more fractures than those with Type I and may have mild to moderate bone deformities. Some may require braces or crutches. The life expectancy for individuals with Type IV OI is normal or near-normal.
Primary Health Complications Affecting Lifespan
In more severe forms of OI, particularly Type III, a shortened lifespan is linked to specific health complications that arise from the underlying collagen defect. Repeated fractures and skeletal deformities can have a cascading effect on other bodily systems. These secondary problems, rather than the fractures themselves, are often the cause of premature mortality.
Respiratory failure is a leading cause of death for individuals with severe OI. Frequent rib fractures and the development of severe spinal curvature, or scoliosis, can alter the shape and size of the chest cavity. These changes restrict the space for the lungs to expand, leading to impaired lung function and an increased susceptibility to respiratory infections like pneumonia.
Cardiovascular problems can also arise and impact longevity. The defective collagen that weakens bones can also affect other connective tissues, including those in the heart and blood vessels. Some individuals with OI may develop issues such as aortic root dilation or problems with heart valves, which can put additional strain on the heart.
Fractures in specific locations pose a significant risk. While any fracture requires care, breaks in certain areas are more dangerous. For example, fractures to the skull can lead to neurological damage. Vertebral fractures can cause compression of the spinal cord or brain stem, leading to serious consequences.
Medical Management to Improve Prognosis
Proactive medical care can improve the quality of life and long-term outlook for individuals with Osteogenesis Imperfecta. Management is not a cure but focuses on reducing fracture rates, correcting deformities, and managing complications. This is achieved through a multidisciplinary team of specialists who address the various ways OI affects the body.
A primary part of medical management involves medications called bisphosphonates. These drugs work by slowing down the natural process of bone breakdown, which helps to increase overall bone density and strength. Bisphosphonate therapy can reduce the frequency of fractures, especially in the spine, and decrease bone pain for many individuals with OI.
Surgical interventions are often necessary to manage the effects of the disorder. One common procedure is the insertion of metal rods, known as intramedullary rodding, into the long bones of the arms and legs. These rods provide internal support, making the bones more resistant to breaking and helping to correct bowing deformities. Surgery may also be required to correct severe scoliosis to improve respiratory function.
Physical and occupational therapy are important components of a care plan. Therapists work with individuals to maximize their mobility, build muscle strength to support fragile bones, and learn how to perform daily activities safely to minimize fracture risk. Low-impact exercises like swimming are often encouraged to maintain strength without putting undue stress on the skeleton.
Consistent and lifelong monitoring is important for anticipating and managing potential health issues. Regular appointments with specialists such as pulmonologists and cardiologists are important for tracking lung function and heart health. Similarly, audiologists are part of the care team, as hearing loss is a common complication in some types of OI.