Myelofibrosis is a type of cancer that affects the bone marrow. The bone marrow is the part of the body that is responsible for forming new blood cells. You may think of the bone marrow as a factory for making blood cells. In myelofibrosis fibrosis, a certain gene mutation causes the bone marrow to produce a lot of blood cells at some stage.

Abnormal cells in the bone marrow start to produce certain substances called cytokines. One of these cytokines is called fibroblast growth factor, which replaces the tissue that forms blood cells by collagen fibrous tissue. This will decrease the bone marrow’s ability to produce new blood cells, so the numbers of all types of blood cells will decrease which is called “pancytopenia.”

1. The abdomen may feel Swollen

The abnormal blood cells may collect in the liver and spleen. Because there is a significant number of them and because they tend to grow rapidly, they can cause the liver and spleen to increase in size. That is why people affected by myelofibrosis will start to feel that their abdomen is swollen. They may also feel fullness or heaviness.