From the Guidelines
The correct answer is (c) myeloid metaplasia results in extramedullary hematopoiesis. Myeloid metaplasia is a condition characterized by the development of hematopoietic tissue outside the bone marrow, most commonly in the liver and spleen. This occurs when the bone marrow is unable to function properly, often due to fibrosis or infiltration by malignant cells. The condition typically affects older adults rather than young females, contradicting option (a) [ 1 ]. Splenomegaly is actually a common finding in myeloid metaplasia as the spleen becomes a site of blood cell production, making option (b) incorrect [ 1 ]. While there may be changes in bone marrow megakaryocytes in some cases, the defining feature is the shift of blood cell production to extramedullary sites, not specifically increased bone marrow megakaryocytes as suggested in option (d) [ 1 ]. Myeloid metaplasia is often associated with myelofibrosis and can be part of myeloproliferative disorders, leading to symptoms such as fatigue, weight loss, and abdominal discomfort from organomegaly [ 1 ]. Some key features of myeloid metaplasia include:
- Extramedullary hematopoiesis in the liver and spleen
- Splenomegaly due to blood cell production
- Association with myelofibrosis and myeloproliferative disorders
- Symptoms such as fatigue, weight loss, and abdominal discomfort It's worth noting that the diagnosis of myeloid metaplasia and its distinction from other myeloid neoplasms can be challenging and requires careful morphologic assessment and consideration of clinical and laboratory findings [ 1 ].
From the Research
Myeloid Metaplasia Characteristics
- Myeloid metaplasia is a chronic myeloproliferative disorder characterized by bone marrow fibrosis and neoangiogenesis, constitutive release of a high number of CD34+ stem cells from the bone marrow, and extramedullary hematopoiesis 2.
- The median age at diagnosis is 60 years, and more than 90% of patients are diagnosed after age 40 years, indicating that it is not a disease of young females 3.
- Myeloid metaplasia is often associated with massive splenomegaly, which is a common clinical manifestation 3, 4.
Clinical Manifestations and Pathogenesis
- Clinical manifestations of myeloid metaplasia include progressive anemia, massive splenomegaly, both hepatosplenic and non-hepatosplenic extramedullary hematopoiesis (EMH), a leukoerythroblastic blood smear, circulating progenitor cells, and marked bone marrow stromal reaction including collagen fibrosis, osteosclerosis, and angiogenesis 4.
- The pathogenesis of myeloid metaplasia is undefined, but the dual action of deregulation of the bFGF pathway may influence myeloproliferation, myelofibrosis, and neoangiogenesis 2.
- Myeloid metaplasia results in extramedullary hematopoiesis, which is a characteristic finding in this condition 5, 3, 4, 6.