Considerations for inherited versus acquired bone marrow failure. Age, evidence of other organ involvement, and family history of cytopenia, hematologic malignancy, solid cancers, or other organ involvement (ie, familial pulmonary fibrosis in telomere biology disorders). Patients with IBMFSs may have had long-standing cytopenias for years; adult patients who present acutely with severe cytopenia more commonly have immune-mediated disease. Low immunoglobulins or lymphocyte subsets may point towards a primary immunodeficiency disorder; these are typically preserved in immune marrow failure. Paroxysmal nocturnal hemoglobinuria clones are commonly seen in immune bone marrow failure but very rare in IBMFS. Many IBMFS have disease specific clonal patterns and somatic genetic rescuing may occur. In immune BMF, PIGA (driver of PNH), BCOR/L1, and human leukocyte antigen mutations predominate. DEB, diepoxybutane.