At a Glance

Bone marrow replacement or myelophthisis causes cytopenias (reductions in peripheral blood components) by destroying or replacing normal hematopoiesis in the bone marrow. Thus, patients may have any combination of anemia, leukopenia, or thrombocytopenia, similar to other bone marrow failure syndromes, such as aplastic anemia. Unlike these other syndromes, however, bone marrow replacement also causes leukoerythroblastosis, which is the appearance of immature leukocytes (“left-shifted” granulocytes) and erythroid precursors (nucleated red blood cells) in the peripheral blood.

What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?

Complete blood count (CBC) with differential will reveal variable cytopenias, ranging from isolated anemia or thrombocytopenia to pancytopenia. In bone marrow replacement due to myeloproliferation, such as in primary myelofibrosis, the leukocyte and/or platelet count may be increased. Differential counts will reveal leukoerythroblastosis with immature leukocytes and nucleated red blood cells. These will also be visible on peripheral blood smear review, along with tear-drop shaped erythrocytes (dacryocytes) and giant platelets.

Confirmation of bone marrow replacement is made by bone marrow biopsy. Trephine core biopsies will show replacement of normal hematopoietic tissue with other cells. These are usually neoplastic, including leukemia, lymphoma, or metastatic carcinoma, but myelophthisis can also be caused by excessive fibrosis, as is seen in primary myelofibrosis, or bony replacement, as in osteosclerosis.(Table 1)

Continue Reading

Table 1.
Hemoglobin Platelet Count Absolute Neutrophil Count
<10 g/dL <100×109/L <1.5×109/L

Are There Any Factors That Might Affect the Lab Results? In particular, does your patient take any medications – OTC drugs or Herbals – that might affect the lab results?

Cytopenias are a non-specific finding. Thus, other causes of bone marrow failure should be considered and ruled out, such as aplastic anemia, medication effects, including cytotoxic chemotherapy and drug-induced neutropenia, toxic insults, infectious processes, and autoimmune disorders. In younger patients, congenital bone marrow failure syndromes, such as Fanconi’s anemia, dyskeratosis congenita, and Shwachman-Diamond syndrome, might be considered. Myelodysplastic syndrome should be in the differential diagnosis for older patients or those with a history of cytotoxic chemotherapy.

What Lab Results Are Absolutely Confirmatory?

Bone marrow biopsy is the gold standard for evaluation of bone marrow replacement.