Leukemia: Step 1 review notes and self-test
Notes for the Leukemia rapid review: the clue that separates each of its 6 confusion pairs, with timestamps and a self-test.
October 21, 2026
This video covers AML, ALL, CML, CLL, bone marrow failure, and the clues that separate similar conditions. Watch the video, then use these notes to test yourself.
Aplastic anemia vs Myelodysplastic syndrome and acute leukemia
Aplastic anemia has hypocellular fatty marrow, MDS has dysplastic ineffective marrow, and acute leukemia has marrow replaced by blasts. All can cause pancytopenia, so you should use marrow cellularity, dysplasia, and blast percentage to separate them.
Aplastic anemia vs Myelodysplastic syndrome and acute leukemia Aplastic anemia is empty marrow; MDS is dysplastic ineffective marrow; acute leukemia is blast-filled marrow. Open the comparison and video →Acute leukemias vs Chronic leukemias
Acute leukemias cause rapid marrow failure from blasts, while chronic leukemias have mature clonal cells. ALL has lymphoblasts, AML has myeloblasts, CLL has smudge cells, and CML has BCR-ABL, granulocytic expansion, and low LAP. A high white count is nonspecific, so you should use cell maturity, lineage markers, and signature smear or genetic clues.
Acute leukemias vs Chronic leukemias Acute equals blasts and rapid marrow failure; chronic equals mature clonal cells with CLL smudge cells or CML BCR-ABL myeloid expansion. Open the comparison and video →Acute promyelocytic leukemia vs Other AML
APL has abnormal promyelocytes, many Auer rods, t(15;17) PML-RARA, and a high risk of DIC. Other AML has myeloblast proliferation but lacks this promyelocyte and DIC pattern. Auer rods can occur across AML, so you should not identify APL from Auer rods alone.
Acute promyelocytic leukemia vs Other AML APL is AML plus promyelocytes, t(15;17), and DIC; other AML is myeloblast disease without that emergency signature. Open the comparison and video →CML vs Leukemoid reaction
CML is a BCR-ABL clonal myeloid disease with basophilia and low LAP, while a leukemoid reaction is reactive neutrophilia with high LAP and no BCR-ABL. Both can cause very high neutrophil counts and a left shift, so you should use BCR-ABL, basophils, LAP, and the clinical trigger to separate them.
CML vs Leukemoid reaction CML is BCR-ABL clonal myeloid disease with low LAP; leukemoid reaction is reactive neutrophilia with high LAP. Open the comparison and video →Polycythemia vera vs Secondary polycythemia
Polycythemia vera has a JAK2 mutation and low EPO, while secondary polycythemia is driven by high EPO from hypoxia or an EPO source. Both raise hemoglobin and hematocrit, so you should use the EPO level and JAK2 testing as the fastest separator.
Polycythemia vera vs Secondary polycythemia PV is JAK2-high red cells with low EPO; secondary polycythemia is EPO-high red cells from hypoxia or EPO source. Open the comparison and video →Primary myelofibrosis vs Aplastic anemia
Primary myelofibrosis has fibrotic marrow, a dry tap, teardrop RBCs, leukoerythroblastosis, massive splenomegaly, and extramedullary hematopoiesis. Aplastic anemia has hypocellular fatty marrow without splenomegaly or a teardrop leukoerythroblastic picture. Both can cause pancytopenia, so teardrop cells, splenomegaly, and a dry tap point you toward fibrosis rather than aplasia.
Primary myelofibrosis vs Aplastic anemia Myelofibrosis is scarred marrow with teardrops and big spleen; aplastic anemia is empty marrow without extramedullary hematopoiesis. Open the comparison and video →Quick self-test
Name the diagnosis from the clue, then tap to check.
____ is hypocellular fatty marrow with pancytopenia, low reticulocytes, no splenomegaly, and no teardrop leukoerythroblastic picture.
Aplastic anemia · Primary myelofibrosis vs Aplastic anemia
____ is EPO-driven erythrocytosis from hypoxia, high altitude, smoking, sleep apnea, cyanotic heart disease, renal disease, or EPO-producing tumors.
Secondary polycythemia · Polycythemia vera vs Secondary polycythemia
____ is reactive neutrophilia from infection, inflammation, stress, or cytokine drive, often with toxic granulation, high LAP, and no BCR-ABL.
Leukemoid reaction · CML vs Leukemoid reaction
ALL and AML present with rapid marrow failure from blasts; ALL is lymphoblast disease, while AML is myeloblast disease often with Auer rods and myeloperoxidase positivity.
Acute leukemias · Acute leukemias vs Chronic leukemias
____ is AML with abnormal promyelocytes, many Auer rods, t(15;17) PML-RARA, and high DIC risk.
Acute promyelocytic leukemia · Acute promyelocytic leukemia vs Other AML
____ causes hypocellular fatty marrow with pancytopenia, low reticulocytes, and no malignant blast expansion.
Aplastic anemia · Aplastic anemia vs Myelodysplastic syndrome and acute leukemia
____ subtypes have myeloblast proliferation with cytopenias, Auer rods or MPO positivity, but lack the PML-RARA promyelocyte/DIC pattern.
Other AML · Acute promyelocytic leukemia vs Other AML
____ is clonal myeloproliferation with marrow fibrosis, dry tap, teardrop RBCs, leukoerythroblastosis, massive splenomegaly, and extramedullary hematopoiesis.
Primary myelofibrosis · Primary myelofibrosis vs Aplastic anemia
____ is a primary myeloproliferative neoplasm with increased red cell mass, often leukocytosis/thrombocytosis, pruritus after hot showers, splenomegaly, JAK2 mutation, and low EPO.
Polycythemia vera · Polycythemia vera vs Secondary polycythemia
Chronic myeloid leukemia causes clonal granulocytic expansion with splenomegaly, basophilia, Philadelphia chromosome t(9;22), BCR-ABL, and low leukocyte alkaline phosphatase.
Keep going
Every pair in this review has a free page in the library with a side-by-side comparison and a practice question. Work through the ones you missed in the self-test first.