Bone Mineral Density and Hemophilia
By Dr. David Clark
We know that people with hemophilia have lower bone mineral density (BMD), which can lead to osteoporosis. We just don’t know why. Two recent studies have looked at two different aspects of this condition.
11/12/24 A group from Germany looked to see whether there is a correlation between hemophilia severity and BMD. In 255 patients with hemophilia from a single treatment center, they found that 63% showed reduced BMD. The data were collected by dual x-ray absorptiometry (DXA) scans of the patient’s femoral neck (the top of the thigh bone where it goes into the hip joint) and the lumbar (lower) spine. They found significantly lower BMD in patients with severe hemophilia than in mild patients. Moderate hemophilia patients were in between with BMDs not significantly different from either the severe or mild patients. Previous research has suggested that joint damage affects BMD and the results here were in agreement.
Interestingly, they found that the fracture risk in the patients with osteoporosis was actually lower than in the general population, although other studies have shown the opposite. This concurs with a previous study that suggested than hemophilia patients have few bone fractures despite osteoporosis. The study showed little effect of HIV or HCV (hepatitis C virus) infection on BMD, although other studies have shown an effect. They also found that about 19.2% of subjects had a vitamin D deficiency, compared with 30.8% of the male German population. Vitamin D is important for bone health. The authors suggest routine screening for low BMD in hemophilia patients starting at age 30. [Ransmann P et al., Res Pract Thromb Haemost, online ahead of print 11/12/24]
10/23/24 A group of Italian researchers studied the effects of clotting factors on bone cells. Bone cells include osteoblasts, which continuously produce new bone, and osteoclasts, which continuously break down bone (resorption). Bone is continuously being formed and broken down, so the balance between the activities of these two cell types is important for bone health.
Their results showed that factor VIII, von Willebrand factor, activated factor X and thrombin can inhibit bone breakdown, which presumably leads to stronger bone. They found that activated factor IX had no effect on bone breakdown, which is in contrast to an animal study that showed that IX-deficient mice show reduced BMD and osteoporosis. This suggests that factor IX might have an effect on another part of the bone production/resorption process, rather than directly on bone cells. It has been suggested in other studies that factor IX does not have a direct effect. Instead, factor IX may help increase production of thrombin which then affects bone cells. [Battafarano G et al., Sci Reports, online ahead of print 10/23/24]