primary myeloid metaplasia
pri·mar·y my·e·loid met·a·pla·si·a
myeloid metaplasia occurring as the primary condition, often in association with myelofibrosis.
Synonym(s): agnogenic myeloid metaplasia
chronic idiopathic myelofibrosisA 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.
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.
Bone marrow biopsy.
No specific therapy; packed RBCs for anaemia; androgens may reduce transfusion requirements, but are poorly tolerated in women; recombinant erythropoietin.
Survival ± 5 years, often progresses to acute leukaemia.
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).