Leukoerythroblastosis: Description, Causes and Risk Factors:
Any anemic condition resulting from space-occupying lesions in the bone marrow; the circulating blood contains immature cells of the granulocytic series and nucleated red blood cells, frequently in numbers that are disproportionately large in relation to the degree of anemia.
Leukoerythroblastosis is an uncommon disease characterized by the presence of leukocytosis and erythroid and myeloid blast cells in the peripheral blood. It has been reported in association with juvenile myelomonocytic leukemia, hemolytic anemia
, osteopetrosis, myelofibrosis, and neuroblastoma in the newborn and during childhood. The most common etiological factors for leukoerythroblastosis occurring during early childhood are viral infections, juvenile myelomonocytic leukemia, and osteopetrosis. Human parvovirus B19 infection has been associated with red cell aplasia, leukopenia, and thrombocytopenia. Parvovirus B19 infects the erythroid progenitor cells and causes transient erythroblastopenia and may present as erythema infectiosum in children. However, a transient increase in leukocyte and platelet counts has also been reported. Leukoerythroblastosis has been reported in association with infection by parvovirus B19 in a preterm infant.
The etiological factors during early childhood are congenital-postnatal viral infections, juvenile myelomonocytic leukemia, myelofibrosis, and osteopetrosis. Acute parvovirus B19 infection may present as erythema infectiosum in children. Parvovirus B19 infects the erythroid progenitor cells and causes transient erythroblastopenia and is usually associated with red cell aplasia, leukopenia, and thrombocytopenia. However, transient increases in leukocyte and platelet counts have also been reported.
The most common cause is replacement of bone marrow by metastatic cancer (most often, breast or prostate; less often, kidney, lung, adrenal, or thyroid); extramedullary hematopoiesis tends to be modest. Other causes include myeloproliferative disorders (especially late-stage or spent polycythemia vera), granulomatous diseases, and (lipid) storage diseases. Myelofibrosis can occur in all of these.
Factors that may contribute to decreased RBC production include a decreased amount of functioning hematopoietic tissue, disordered metabolism related to the underlying disorder, and, in some cases, erythrophagocytosis
. Extramedullary hematopoiesis or disruption of the marrow sinusoids causes release of immature cells. Abnormally shaped RBCs often result in increased RBC destruction.
It can also occur as a response to severe critical illness, such as trauma, septicaemia, massive hemolysis, or severe megaloblastic anaemia. Leukoerthyroblastic change refers to the presence of nucleated red blood cells and primitive white blood cells.
Other Risk Factors:
Metastatic carcinoma in th bone marrow.
- Multiple myeloma.
- Hodgkin lymphoma.
- Non-Hodgkin lymphoma and histocytic tumours.
- Miliary tuberculosis.
- Severe megaloblastic anaemia.
- Servere haemolysis, particularly in the young.
- Osteopetrosis (Albers-Schonberg disease).
Myeloid metaplasia may result in splenomegaly, particularly in patients with storage diseases. In severe cases, symptoms of anemia and of the underlying disorder may be present. Massive splenomegaly can cause abdominal pressure, early satiety, and left upper quadrant abdominal pain; hepatomegaly may be present. Hepatosplenomegaly is rare with myelofibrosis from malignant tumors.
The first test for diagnosis leukoerythroblastosis involves looking at a small sample of blood under a microscope. Leukoerythroblastosis is suggested by the presence of red blood cells that contain nuclei or are teardrop-shaped (dacryocytes), or immature granulocyte precursor cells which indicates leukoerythroblastosis is occurring because the displaced hematopoietic cells begin to undergo extramedullary hematopoiesis. These immature granulocytes are seen in peripheral blood smears. Diagnosis is confirmed when a bone marrow biopsy demonstrates significant replacement of the normal bone marrow compartment by fibrosis, malignancy or other infiltrative process. The presence of immature blood cell precursors helps distinguish another cause of pancytopenia, aplastic anemia, from myelophthisic anemia because in aplastic anemia the hematopoietic cells are damaged and immature blood cells are not seen in the peripheral blood.
X-rays, if obtained incidentally, may disclose bony lesions (myelosclerosis) characteristic of long-standing myelofibrosis or other osseous changes (i.e., osteoblastic or lytic lesions of a tumor), suggesting the cause of anemia.
First, the underlying disorder is treated. In idiopathic cases, management is supportive. Erythropoietin (20,000 to 40,000 units sc once/wk or twice/wk) and corticosteroids (eg, prednisone 10 to 30 mg p.o. once/day) have been used, but only modest responses have been observed. Hydroxyurea (500 mg p.o. once/day or once every other day) decreases spleen size and normalizes RBC values in many patients, but the response requires 6 to 12 mo of treatment. Thalidomide (50 to 100 mg p.o. once/day in the evening) may provide modest responses, but it increases the risk of thrombosis and causes fatigue, which can be severe.
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