myeloid metaplasia


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metaplasia

 [met″ah-pla´zhah]
the change in the type of adult cells in a tissue to a form abnormal for that tissue. adj., adj metaplas´tic.
agnogenic myeloid metaplasia the primary or idiopathic form of myeloid metaplasia, which is often accompanied by myelofibrosis; it is considered one of the myeloproliferative disorders. Called also aleukemic or nonleukemic myelosis.
myeloid metaplasia the occurrence of myeloid tissue in extramedullary sites; specifically, a syndrome characterized by splenomegaly, anemia, nucleated erythrocytes and immature granulocytes in the circulating blood, and extramedullary hematopoiesis in the liver and spleen. The primary form is called agnogenic myeloid metaplasia. The secondary or symptomatic form may be associated with various diseases, including carcinomatosis, tuberculosis, leukemia, and polycythemia vera.

my·e·loid met·a·pla·si·a

a syndrome characterized by anemia, enlargement of the spleen, nucleated red blood cells and immature granulocytes in the circulating blood, and conspicuous foci of extramedullary hemopoiesis in the spleen and liver; may develop in the course of polycythemia rubra vera; there is a high incidence of development of myeloid leukemia.

chronic idiopathic myelofibrosis

A chronic progressive condition characterised by panmyelosis and variable marrow fibrosis, massive splenomegaly secondary to extramedullary haematopoiesis, and leukoerythroblastic anaemia with dysmorphic red blood cells, circulating normoblasts, immature white blood cells and atypical platelets.
 
Clinical findings
Patients are often > age 50, suffer from insidious weight loss, anaemia, and abdominal discomfort due to splenomegaly, often with hepatomegaly; 80% have nonspecific chromosome defects.
 
Diagnosis
Bone marrow biopsy.
 
Management
No specific therapy; packed RBCs for anaemia; androgens may reduce transfusion requirements, but are poorly tolerated in women; recombinant erythropoietin.
 
Prognosis
Survival ± 5 years, often progresses to acute leukaemia.

Terminology
No name used for this condition has proven consistently satisfactory to those who work in the field. Chronic idiopathic myelofibrosis is preferred by the World Health Organisation, while others prefer the term primary myelofibrosis. None of the terms fully take into account the functional defects—e.g., haemopoietic stem cell disturbance, extramedullary haemopoiesis and the pathological changes seen in the bone marrow (e.g., intense marrow fibrosis).

my·e·loid met·a·pla·si·a

(mī'ĕ-loyd met'ă-plā'zē-ă)
A syndrome characterized by anemia, enlargement of the spleen, nucleated red blood cells and immature granulocytes in the blood, and foci of extramedullary hemopoiesis in the spleen and liver; may develop in the course of polycythemia rubra vera; there is a high incidence of development of myeloid leukemia.
References in periodicals archive ?
Chronic idiopathic myelofibrosis (CIMF) is characterized by splenomegaly, myeloid metaplasia and reactive bone marrow fibrosis, and it has the highest karyotype aberration rate (1-3).
Cytogenetic studies and their prognostic significance in agnogenic myeloid metaplasia: a report on 47 cases.
FINAL DIAGNOSIS: Pilomatricoma with extensive areas of calcification and ossification and evidences of myeloid metaplasia, secondarily complicated by an organized hematoma.
(2005) Activating mutation in the tyrosine kinase JAK2 in polycythemia vera, essential thrombocythemia, and myeloid metaplasia with myelofibrosis.
Myelofibrosis with myeloid metaplasia. N Engl J Med 2000; 342: 1255-1265, doi: 10.1056/NEJM200004273 421706.
Differential expression of transforming growth factor-beta, basic fibroblast growth factor, and their receptors in CD34+ hematopoietic progenitor cells from patients with myelofibrosis and myeloid metaplasia. Blood 1996; 88: 4534-4546.
The term myeloproliferative neoplasms (MPN) was first introduced by William Dameshek in 1951 to emphasize the clinicopathological similarities between chronic myeloid leukemia (CML), essential thrombocythemia (ET), polycythemia vera (PV), and myeloid metaplasia (MMM) (Also known as, chronic idiopathic myelofibrosis or primary myelofibrosis).2 Accordingly, these 4 disorders are currently referred to as "classic" MPN.
Myelofibrosis with myeloid metaplasia: clinical and haematological parameters predicting survival in a series of 133 patients, B J Hematol.

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