Mastering Medical
USMLE Step 1 · Hematology & Oncology

Aplastic anemia vs Myelodysplastic syndrome and acute leukemia

How to tell Aplastic anemia and Myelodysplastic syndrome and acute leukemia apart when a board question makes them look alike.

Fastest separator

Aplastic anemia is empty marrow; MDS is dysplastic ineffective marrow; acute leukemia is blast-filled marrow.

Side by side

Aplastic anemiaMyelodysplastic syndrome and acute leukemia
Key clue

Aplastic anemia causes hypocellular fatty marrow with pancytopenia, low reticulocytes, and no malignant blast expansion.

Myelodysplastic syndrome causes dysplastic ineffective hematopoiesis with cytopenias; acute leukemia causes marrow replacement by blasts with infection, bleeding, bone pain, or organ infiltration.

Mechanism

Stem cell failure, often immune mediated or toxin/drug/radiation related, leaves marrow empty and unable to produce blood cells.

MDS is clonal abnormal hematopoiesis with ineffective maturation; acute leukemia is malignant blast proliferation that crowds out normal marrow.

Labs and tests

Pancytopenia, very low reticulocyte count, hypocellular marrow, and absence of splenomegaly or blasts support aplastic anemia.

Dysplastic cells and cytopenias support MDS; blasts in blood or marrow, Auer rods in AML, or lymphoblast markers in ALL support acute leukemia.

The trap

All can cause pancytopenia, so marrow cellularity, dysplasia, and blast percentage drive the answer.

Watch it explained

In the rapid reviewLeukemia for USMLE Step 1: AML, ALL, CML, CLL & Bone Marrow Failure
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The repair move

For pancytopenia, do not stop at low counts; ask whether marrow is empty, dysplastic, or packed with blasts.

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Core

A patient has fatigue, recurrent infections, easy bruising, pancytopenia, low reticulocytes, and bone marrow biopsy showing marked hypocellularity with fat replacement and no excess blasts. Which diagnosis is most likely?

Show answer and explanation

Answer: A. Aplastic anemia. Pancytopenia with low reticulocytes and hypocellular fatty marrow points to aplastic anemia.

Why the other choices are tempting

  • B. MDS has dysplastic ineffective hematopoiesis rather than empty marrow.
  • C. Acute leukemia has blast proliferation in marrow.
  • D. Hypersplenism sequesters cells and often has splenomegaly with active marrow.
  • E. Iron deficiency anemia does not cause broad pancytopenia with empty marrow.

Flashcards

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What marrow pattern points to aplastic anemia?

Hypocellular fatty marrow with pancytopenia and low reticulocytes points to aplastic anemia.

What marrow pattern points to acute leukemia?

Marrow packed with blasts points to acute leukemia.

Quick answers

What is the fastest way to tell Aplastic anemia from Myelodysplastic syndrome and acute leukemia?

Aplastic anemia is empty marrow; MDS is dysplastic ineffective marrow; acute leukemia is blast-filled marrow.

What is the key clue for Aplastic anemia?

Aplastic anemia causes hypocellular fatty marrow with pancytopenia, low reticulocytes, and no malignant blast expansion.

What is the key clue for Myelodysplastic syndrome and acute leukemia?

Myelodysplastic syndrome causes dysplastic ineffective hematopoiesis with cytopenias; acute leukemia causes marrow replacement by blasts with infection, bleeding, bone pain, or organ infiltration.

What is the common trap with Aplastic anemia vs Myelodysplastic syndrome and acute leukemia?

All can cause pancytopenia, so marrow cellularity, dysplasia, and blast percentage drive the answer.