Mastering Medical
USMLE Step 1 · Hematology & Oncology

Acute promyelocytic leukemia vs Other AML

How to tell Acute promyelocytic leukemia and Other AML apart when a board question makes them look alike.

Fastest separator

APL is AML plus promyelocytes, t(15;17), and DIC; other AML is myeloblast disease without that emergency signature.

Side by side

Acute promyelocytic leukemiaOther AML
Key clue

Acute promyelocytic leukemia is AML with abnormal promyelocytes, many Auer rods, t(15;17) PML-RARA, and high DIC risk.

Other AML subtypes have myeloblast proliferation with cytopenias, Auer rods or MPO positivity, but lack the PML-RARA promyelocyte/DIC pattern.

Mechanism

PML-RARA blocks promyelocyte differentiation; targeted therapy releases the maturation block with all-trans retinoic acid plus arsenic-based therapy in many protocols.

Other AML subtypes expand malignant myeloid precursors through different mutations and differentiation blocks.

Labs and tests

Promyelocytes, bundles of Auer rods, t(15;17), prolonged PT/PTT, low fibrinogen, and high D-dimer support APL.

Myeloblasts, MPO positivity, cytopenias, and AML-defining genetic changes without t(15;17) support non-APL AML.

The trap

Auer rods can occur in AML broadly, but APL is the Auer-rod-heavy promyelocyte subtype with coagulopathy.

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

When AML appears with bleeding or DIC, check for promyelocytes and t(15;17) immediately.

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Core

A patient has fatigue, bruising, mucosal bleeding, abnormal promyelocytes with numerous Auer rods, low fibrinogen, high D-dimer, and t(15;17). Which diagnosis is most likely?

Show answer and explanation

Answer: A. Acute promyelocytic leukemia. Promyelocytes with t(15;17) and DIC point to acute promyelocytic leukemia.

Why the other choices are tempting

  • B. Other AML lacks the defining PML-RARA promyelocyte/DIC pattern.
  • C. ALL is lymphoblast disease.
  • D. CML is chronic BCR-ABL myeloid proliferation.
  • E. CLL is mature B-cell lymphocytosis.

Flashcards

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What translocation defines APL?

t(15;17) creating PML-RARA defines acute promyelocytic leukemia.

What emergency complication is classic for APL?

DIC with bleeding risk is classic for APL.

Quick answers

What is the fastest way to tell Acute promyelocytic leukemia from Other AML?

APL is AML plus promyelocytes, t(15;17), and DIC; other AML is myeloblast disease without that emergency signature.

What is the key clue for Acute promyelocytic leukemia?

Acute promyelocytic leukemia is AML with abnormal promyelocytes, many Auer rods, t(15;17) PML-RARA, and high DIC risk.

What is the key clue for Other AML?

Other AML subtypes have myeloblast proliferation with cytopenias, Auer rods or MPO positivity, but lack the PML-RARA promyelocyte/DIC pattern.

What is the common trap with Acute promyelocytic leukemia vs Other AML?

Auer rods can occur in AML broadly, but APL is the Auer-rod-heavy promyelocyte subtype with coagulopathy.