3 yrs lytic bone lesions through axial skeleton -skull. extramedullary hematopoiesis. new mri spots on brain-bone marrow expansion. can this be fatal?

Depends: Bone marrow expansion throughout the skeleton typically signals either that the marrow is i appropriately expanding into these compartment such as in a myeloproliferative disorder or the present regions of marrow production are insufficient to keep up with current body needs. Regardless of the cause this is best answered by hands on evaluation, testing and management by an hematologist.