Lab Med Online.  2014 Apr;4(2):112-115.

Acute Megakaryoblastic Leukemia with CD41a-/CD61-/CD42a+ Blasts in an Infant with Down Syndrome

• Ko K
• Kwon MJ
• Jang MA
• Lee ST
• Woo HY
• Park H
• Kim SH

Abstract

Infants with Down syndrome have increased incidences of transient abnormal myelopoiesis (TAM) and acute leukemia, which are usually associated with acute megakaryoblastic leukemia (AMKL). A 5-day-old girl with Down syndrome was diagnosed with TAM; 4 months later, acute leukemic transformation was suspected. Bone marrow (BM) examination was performed, and the infant was diagnosed with acute leukemia (80% blasts). Although BM aspirates showed the presence of megakaryocytic blasts with cytoplasmic blebs, flow cytometry analysis revealed that they were negative for cells with CD41a and CD61 immunophenotypes. Further analysis revealed that the megakaryocyte-related marker CD42a was positive in 57% of blasts. Morphologic and immunophenotypic features are required to establish the lineage of megakaryocytic blasts, which are necessary for diagnosing AMKL. As most cases of AMKL were positive for CD41 and/or CD61 markers, their presence was evaluated during routine analysis. In order to identify the immunophenotypic features of AMKL in an infant with Down syndrome, we performed additional flow cytometry for CD42a, one of the megakaryocytic markers, and were able to assist in the early diagnosis of AMKL, as well as to use CD42a as an effective follow-up marker.

Keyword

Acute megakaryoblastic leukemia; Down syndrome; Immunophenotype; CD42a

MeSH Terms

Blister
Bone Marrow
Cytoplasm
Down Syndrome*
Early Diagnosis
Female
Flow Cytometry
Follow-Up Studies
Humans
Incidence
Infant*
Leukemia
Leukemia, Megakaryoblastic, Acute*
Myelopoiesis

Figure

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  Fig. 1 Bone marrow aspirates showing megakaryoblasts with cytoplasmic blebs (Wright stain, 1,000×).

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  Fig. 2 Flow cytometric analysis showing blast expression with CD41a-/CD61-/CD42a+ immunophenotypes. (A) Almost all leukemic cells showed strong positive expression of CD117, but were negative for CD61. (B) Many leukemic cells were negative for CD41a, but showed positive expression of CD42a. (C) Many leukemic cells showed aberrant expression of CD7.

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  Fig. 3 GATA1 gene analysis showing a known heterozygous mutation (c.-20G>A).

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  Fig. 4 Follow-up flow cytometric analysis showing <1% residual blast cells expressing CD42a+/CD7+ immunophenotypes.

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