**Myelophthisis that may be due to myelofibrosis or to the growth of tumours that replace or displace normal [[Bone Marrow - Anatomy & Physiology|bone marrow]]. The most common type of tumour that cause myelophthisis are myeloproliferative or lymphoproliferative diseases. | **Myelophthisis that may be due to myelofibrosis or to the growth of tumours that replace or displace normal [[Bone Marrow - Anatomy & Physiology|bone marrow]]. The most common type of tumour that cause myelophthisis are myeloproliferative or lymphoproliferative diseases. |