Erythroleukemia

Rare form of acute myelogenous leukemia with predominantly erythroid lineage proliferation.

Can occur at any age, including childhood.

Comprises less than 5% of AML cases.

Also known as Di Guglielmo’s syndrome.

FAB classification requires at least 30% of non-erythroid elements to be type I or II blasts.

M6 type AML with a proliferation of more than 50% erythroblasts and more than 30% myeloblasts.

WHO classification: 2 subtypes 1) pure erythroid leukemia (FAB subtype B)with immature cells committed to the erythroid series with greater than 80% of bone marrow cells involved without a significant myeloblastic component. 2)subtype A has more than 50% erythroid precursors in the nucleated population and more than 20% myeloblasts in the non-erythroid cell population.

Male predominance, bimodal age distribution with a small peak below age 20 and a wider and more definitive peak in the 7th decade.

Almost 50% of cases related to chemotherapy exposure with alkylating agents or occupational exposure to mutagenic agents such as benzene.

May be secondary to a blast crisis in a myeloproliferative disease of the final stages of a myelodysplastic syndrome.

Most common clinical presentation is severe anemia.

One thrid of patients present with hemorrhage (Olopade OI).

20-40% of patient’s have hepatosplenomegaly.

Generally neutropenia and thrombocytopenia are mild.

50% of patients have no peripheral blasts on review of the blood smear.

Peripheral smear may show significant numbers of schistocytes, nucleated red blood cells and pseudo Pelger-Huet cells.

Bone marrow examination reveals hypercellularity with red blood cell dysplasia, megaloblastoid changes manifested by asynchronous nucleo-cytoplasmic maturation, Howell-Jolly bodies, multinucleation and impaired hemoglobinization.

Multilinear dysplasia may be present, and megakaryocytes are often abnormal with segmentation alterations of the nucleus, and the presence of micromegakaryocytes.

Circulating megakaryocytes may be present.

Myeloid dysplasia is seen in up to 50% of patients.

FAB subtype B the undifferentiated form of pure erythroid leukeima manifests with medium to large erythroblasts, with basophilic cytoplasm, round nucleoli and frequent poorly demarcated vacuoles that are often PAS positive.

FAB subtype B cells are myeloperoxidase negative, positive for alpha napthyl acetate esterase, acid phosphatase and PAS.

PAS may be positive may be seen in pronormoblasts and basophilic normoblasts in AML M6.

PAS stains are always negative in normal erythroid differentiation.

Markers include glycophorin A and CD 36.

Glycophorin A may be negative in some cases of AML M6b, because it is a late erythroid marker.

CD36 a nonspecific marker detects erythroid precursors at earlier stages of differentiation.

CD71 expression may be signficantly low in erythroleukemia.

Blasts are often negative for HLA-DR and CD34, but may be positive for CD117.

Clonal chromosomal abnormalities found in 70-100% of patients.

Loss of all or part of the long arm of -5/del(5q), -7/del(7q), and trisomy 8 seen in 65% of denovo patients and secondary AML-M6

Incidence of patients of unfavorable karyotypes higher than in other types of AML. wit inv 3, 11q23 and 17p abnormalities (Park S).

Must be differentiated from refractory anemia with excess blasts, AML with myelodysplastic changes, megaloblastic anemia due to vitamin B12 deficiency.

Usually associated with poor prognosis.

Treatment with anthracycline and cytosine arabinoside associated with a complete remission rate of approximately 50-60%.

Median survival 4-5 months and survival rate related to karyotype abnormalities (Olopade OI).

For patients with 5q or 7q abnormalities allogeneic bone marrow transplantation is the best option because of the poor prognosis of these subtypes.

Complete remission rates for patients with 5q and 7q abnormalities is approximately 20% and median survival of 16 weeks, compared to 77% for patients without these abnormalities (Olapade OI).

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