myelofibrosis is a disorder of the bone marrow that affects the production of blood cells and may lead to blood cells being produced in the spleen or liver instead of the bone marrow  - you can read more <a href="https://www.macmillan.org.uk/information-and-support/blood-cancer/blood-disorders-neoplasms/myelofibrosis.html" target="_blank" rel="noopener">here</a>