What is hyperviscosity, why does it occur and how it it managed?

What is hyperviscosity, why does it occur and how is it managed? Viscosity of any fluid, which, essentially in very simple terms as a non-physicist, just tells you about the thickness of that fluid. And here we are concerned about the viscosity of blood or plasma, which is circulating in our bloodstream. And there are situations where our blood becomes thick or more viscous, which is not good for circulation because it can cause problems and symptoms that can become potentially life-threatening. So when the viscosity of the circulating blood or plasma becomes high or goes up, that is by definition, hyperviscosity.

What causes hyperviscosity? There are two broad categories or two main reasons for hyperviscosity. Either we have more blood cells, especially more red cells or white cells, or we have a high amount of protein in the blood, especially larger protein elements. So from myeloma perspective, and from Waldenstrom’s macroglobulinemia perspective, which is a related disease, the high viscosity is caused by a high protein level in the blood. It could be either a very high IgM level in Waldenstrom’s macroglobulinemia or a very high level of IgG or IgA level. IgM is more commonly associated with hyperviscosity because it is a bigger molecule, and as a result it makes blood thicker, faster.

Why is hyperviscosity bad? Because it affects circulation and patients have symptoms. So if patients develop hyperviscosity, they can note these symptoms that essentially point towards interference with the flow of blood and the more common symptoms associated with hyperviscosity, or some kind of bleeding. These patients tend to have bleeding from the nose or gums. So that is one symptom associated with hyperviscosity. The second symptom that is common with hyperviscosity, again, it's because of the flow of blood in the retina or eye. And these patients can have some visual blurring and floaters and situations like that. So visual symptoms with some bleeding. And then this can also cause neurologic symptoms. Patients may notice dizziness; they may have confusion. Some patients may present with shortness of breath. And in extreme cases, it can even cause seizures and coma. But again, luckily most of the patients present early, especially depending on the type of disease. When we suspect that, we do the right tests and that way we can help, which can help us in making the diagnosis.

That is the definition of hyperviscosity, especially as it pertains to plasma cell disorders as well as Waldenstrom macroglobulinemia. Just one additional point is that there are other situations, like a condition called polycythemia, where the cause is different. These patients have a very high concentration of red blood cells. Because this is an abnormal condition, their body is making more red cells. And that thickness of red cells affects circulation. These patients can also present with hyperviscosity.

If you had hyperviscosity in your blood, once your myeloma gets treated and protein levels begin to drop, would it go back to normal? Myeloma patients, unfortunately, do not suffer that much from hyperviscosity as Waldenstrom’s patients do. But yes, absolutely. It is directly related to the amount of protein in the blood. So if someone starts out with an M protein of eight grams and an IgG level of 13 grams, and once you give that patient, say, two cycles of induction treatment and the total protein level goes down, IgG level goes down and protein goes down, with that viscosity goes down and the symptoms go away.

But there are other ways of treating hyperviscosity symptoms relatively rapidly. This includes a procedure called plasmapheresis, where basically you connect, through a venous catheter or a line, the patient’s blood to a machine, and the blood can circulate through the machine, which is designed or programmed to take out excess variety so that one can relieve the symptoms right away. Within a few hours, you can remove the excess protein. But then this is not the definitive measure because the underlying cause, which is increased production of protein, persists. So that has to be treated with myeloma or Waldenstrom’s treatment. But a procedure like plasmapheresis or plasma exchange can rapidly lower the protein and help relieve the symptoms.