By Dr. David Clark

12/6/23  We don’t know exactly what, on a molecular level, causes hemophilic joint damage.  We know it’s caused by bleeding into the joints and there is evidence that iron from the hemoglobin in the blood is involved.  In the last issue, we saw that a protein called YKL-40 is probably involved.  Now another piece of the puzzle is becoming clear.  A group from China has now shown that the excess iron from the blood can trigger macrophages to transform into an inflammatory form.  Macrophages are a type of white blood cell, part of the immune system.  When you bleed into a joint, macrophages are one of the types of immune cells that arrive at the bleeding site to clean up the mess.  Chronic inflammation from repeated bleeds leads to damage to the synovial tissue around the joint, which is called synovitis.  [Pang N et al., Haemophilia, online ahead of print 12/6/23]