This is part one of a two part case.
A three year old male with Down Syndrome presents with a limp and refusal to bear weight. He says his legs hurt. An examination shows petechiae and purpura on legs. You decide to draw some labs and find that he is anemic and thrombocytopenic with normal WBCs. A Wright's stain of the bone marrow aspirate looks like this:
Challenge: What's the most likely diagnosis?
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