What The Heck Is A Bone Marrow Transplant Anyway?

According to the dictionary app on my computer:

TRANSPLANT (v): to move or transfer (something) to another place or situation, typically with some effort or upheaval; to replant (a plant) in another place; to remove (living tissue or an organ) and implant in another part of the body or in another body.

Ok, a transplant seems easy enough to understand. Now, let's add a bunch of confusing words and letters!

BMT, PBSCT, hematopoietic, SCT, HSCT, autologous, allogeneic, syngeneic, GHVD, cGHVD, immunossuppressantssssss...

What just happened? Let's face it, transplants are complicated. Every time I try to explain my transplant to a friend, I talk myself into a corner or run away screaming about witchcraft and sorcery. There are so many different types of transplants, different ways to obtain transplant material, different ways to transplant that material... medical science has advance to confusing and exhausting heights.

What is bone marrow?

For me, the key to understanding a transplant is to understand what bone marrow is.

In bone marrow lives hematopoietic stem cells, also known as blood-forming stem cells.

Hematopoietic stem cells perform a variety of tasks including. They (1) divide into more blood-forming stem cells or (2) mature into one of three types of blood cells: white blood cells (infection fighters), red blood cells (oxygen mules), and platelets (blood clotters).    

You can find hematopoietic stem cells in not only bone marrow, but in the bloodstream (called peripheral blood stem cells, or PBSCs), or in umbilical cords.

Cells from all these sites can be used in a transplant. (Check out this post to see what color stem cells are!)

Wait, I thought a bone marrow transplant meant you harvested bone marrow and transplanted it into someone else. What's all this talk about hemato...whatevers? 

Basically, a transplant involves the stem cells found in the bone marrow, so often a bone marrow transplant (BMT) and a stem cell transplant (SCT) are interchangeable. These days, (to clear up confusion - or add confusion), a more general term can be used: hematopoietic stem cell transplant (HSCT).  

Originally doctors thought that hematopoietic stem cells could only be found in the bone marrow, hence the term bone marrow transplant, BMT. In the old days a BMT involved invasive surgeries for both the donor and recipient, where they would take a chunk of bone. (These types of transplants only happen now in very RARE circumstances because it is very dangerous.)

These days, however, the discovery of hematopoietic stem cells in the bloodstream has changed both how stem cells are harvested from the donor and how they are transplanted into the recipient. A peripheral blood stem cell transplant (PBSCT) is the most COMMON type of transplant with regards to leukemias and blood cancers.

PBSCT are less invasive and relatively painless for both donor and recipient. (More on donating PBSCs/bone marrow later this month.)

So, why all the acronyms?

I don't know, really. Doctors seem to love 'em. Here are some acronyms you may have heard:

BMT: Bone Marrow Transplant
SCT: Stem Cell Transplant
PBSCT: Peripheral Blood Stem Cell Transplant (often shorted to SCT)
HSCT: Hematopoietic Stem Cell Transplant
GVHD: Graft Versus Host Disease (Stay tuned for more about GVHD)
cGVHD: Chronic Graft Versus Host Disease
TGIF: Thank God It's Friday (See tomorrow)