Myelophthisis refers to the displacement of hemopoietic bone-marrow tissue[1] by fibrosis, tumors, or granulomas.

The word comes from the roots myelo-, which refers to bone marrow, and phthisis, shrinkage or atrophy.

Myelophthisis can occur in the setting of chronic myeloproliferative disease (e.g. myelofibrosis), leukemia, lymphoma, and metastatic carcinoma or myeloma.

[2] Currently, the most common cause is displacement of bone marrow by metastatic cancer (extramedullary hematopoiesis tends to be modest).

Some cases of myelophthisis are thought to be related to the release of cytokines that simulate fibroblastic proliferation and fibrosis in the marrow.