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Results from the First Report on Fracture Prevalence in Patients with Sickle Cell Disease

"We know that patients with thalassemia have poor bone health, but we didn't have a lot of information on patients with sickle cell disease, with or without iron-overload. This is one of the first studies to look at fracture prevalence in sickle cell disease."

This month in Bone, CHORI investigators Ellen Fung, PhD and Elliott Vichinsky, MD, chief of the division of Hematology/Oncology at CHRCO, along with CHRCO clinical scientist Paul Harmatz, MD, report the latest results on fracture prevalence in sickle cell disease from a series of analyses conducted as part of the Multi-Center Study of Iron Overload.

Utilizing subjects recruited from nearly 30 different clinical hematology centers from the United States, Canada and the United Kingdom, the Iron Overload study was a 4 year longitudinal natural history study that crossed international boundaries in order to gather first-time comparative data on iron overload in patients with thalassemia and sickle cell disease (SCD).

As Dr. Fung explains, "We have a tremendous amount of understanding of iron-overload in patients with thalassemia as they've been followed very closely for many years. Iron overload is a relatively new phenomenon in sickle cell patients, so our understanding of what iron does to patients with sickle cell disease is less developed."

In the latest Bone publication, Drs. Fung, Vichinsky and their colleagues report that although sickle cell patients do not have the same level of endocrine disorders that are highly predictive of bone fracture typically seen with thalassemia, SCD patients have a higher than normal risk for bone fracture, when you consider their level of physical activity.

"Most healthy teenagers have a pretty high rate of fracture, primarily in the forearms," explains Dr. Fung. "An increase in contact sports participation occurs at the same time as the typical growth spurt. There's a natural discrepancy, which combined with the right insult, leads to fractures."

In kids with SCD, however, the fractures aren't caused by this typical convergence of factors. With such low hemoglobin values, kids with SCD are generally much less active than their healthy counterparts, as they don't often have the energy to be as physically active.
"Most of the teens with sickle cell disease are not playing competitive sports, yet we're still seeing fractures in this young a cohort. The fact that these kids are still fracturing even though they are not super active is significant."
In addition, there was a relatively high predominance of fractures in the spine, back and pelvis - about 10 percent. These kinds of fractures occur more frequently in either adults over 50, particularly post-menopausal women, or in patients who have suffered significant trauma, such as a motor vehicle accident - not in kids under the age of 25.

"The reason for the majority of the fractures in this cohort was not the result of recreational activity, but the result of falls," Dr Fung says. "We would consider them low trauma fractures, which are very atypical for this age group in the normal population."

Although the current results are limited by self-reporting of fractures and the lack of a large cohort of healthy patients who were of the same ethnicity as the majority of SCD patients, who are predominantly African American, important conclusions can still be drawn. In particular, the study highlights that there are more issues than pain management to consider when addressing the needs of SCD patients.

"We've been focusing on pain for years and years because that is the most prevalent problem in sickle cell disease, and that's what causes the most chaos for families," points out Dr. Fung. "But there are many other chronic problems as well with SCD, and it's clear from this study that fracture is one of them."

Of course, it's only through identifying such problems, that better care can be developed to treat, and hopefully prevent, such problems from developing in the first place.

"Fracture can lead to other morbidities such as pain, deformity, loss of independence, diminished quality of life and immobilization as well as absence from work and school. We want to remove fracture from the equation, and to do that we need to begin monitoring bone health early in life," says Dr. Fung.


Tuesday, May 17, 2011 8:19 AM

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