AIM • STEP 10
Student Memory Support
Hemolytic Anemias and Hemoglobinopathies
3rd Year MBBS • Blood and Immunology • High-yield memory reinforcement and last-minute revision
1. High-Yield Flashcards
Tap each question to reveal the answer.
What membrane change produces spherocytes in hereditary spherocytosis?
Loss of membrane surface area relative to cell volume.
Why are spherocytes preferentially destroyed in the spleen?
They have reduced deformability and cannot pass easily through splenic cords.
Which test helps distinguish hereditary spherocytosis from immune hemolysis?
Direct antiglobulin test: negative in hereditary spherocytosis, positive in immune hemolysis.
What is the β-globin amino-acid substitution in sickle cell disease?
Valine replaces glutamic acid at position 6 of β-globin.
What triggers red-cell sickling at the molecular level?
Polymerization of deoxygenated HbS.
Which two major pathological consequences result from sickling?
Chronic hemolysis and vaso-occlusion.
Why does hydroxyurea reduce sickling-related complications?
It increases HbF, which reduces HbS polymerization.
What is the main pathological problem in β-thalassemia?
Excess unpaired α chains cause ineffective erythropoiesis and hemolysis.
What hemoglobin forms when three α-globin genes are affected?
HbH, composed of β₄ tetramers.
What hemoglobin is associated with loss of all four α-globin genes in fetal life?
Hb Bart’s, composed of γ₄ tetramers.
What protective pathway fails in G6PD deficiency?
NADPH generation is reduced, so glutathione cannot remain adequately reduced.
Which two morphological clues suggest oxidant injury in G6PD deficiency?
Heinz bodies and bite cells.
What is the fundamental acquired defect in PNH?
PIGA mutation causing deficient GPI anchors and loss of CD55/CD59.
How do warm- and cold-antibody immune hemolysis differ mechanistically?
Warm disease is mainly IgG-mediated splenic hemolysis; cold disease is mainly IgM-mediated complement activation.
2. Mnemonics
Mnemonic Title: Hereditary Spherocytosis Membrane Proteins
SABP
Meaning: Spectrin • Ankyrin • Band 3 • Protein 4.2
Mnemonic Title: Oxidant Hemolysis Sequence
N-G-H-B
Meaning: NADPH falls → Glutathione protection falls → Heinz bodies form → Bite cells appear.
Mnemonic Title: PNH Core Pathway
P-G-C
Meaning: PIGA mutation → GPI-anchor deficiency → Complement-sensitive blood cells.
3. Memory Tables
Hereditary Spherocytosis vs Warm Immune Hemolysis
| Feature | Hereditary Spherocytosis | Warm Immune Hemolysis |
|---|---|---|
| Core defect | Membrane protein abnormality | IgG-mediated RBC coating |
| Smear | Spherocytes | Spherocytes |
| DAT | Negative | Positive |
| Main site | Spleen | Spleen |
Major Hemolytic Disorders — One-Line Differentiation
| Disorder | Key Morphology | Key Diagnostic Clue |
|---|---|---|
| Hereditary spherocytosis | Spherocytes | EMA abnormal, DAT negative |
| Sickle cell anemia | Sickle cells | Hb electrophoresis/HPLC |
| Thalassemia | Microcytosis, target cells | Hb analysis/genetic testing |
| G6PD deficiency | Bite cells, Heinz bodies | G6PD enzyme assay |
| PNH | No single hallmark smear pattern | Flow cytometry for GPI-linked proteins |
4. Rapid Revision Points — Last-Minute Revision
Must Remember:
- Hereditary spherocytosis causes predominantly extravascular hemolysis in the spleen.
- Sickle cell disease combines hemolysis with vaso-occlusion.
- Howell–Jolly bodies in sickle cell disease indicate functional asplenia.
- β-thalassemia produces ineffective erythropoiesis because excess α chains injure erythroid precursors.
- β-thalassemia trait characteristically shows increased HbA₂.
- Mild α-thalassemia may have normal adult hemoglobin electrophoresis.
- G6PD deficiency causes oxidant-induced hemolysis through inadequate glutathione protection.
- A G6PD assay may appear normal during acute hemolysis because older deficient cells have already been destroyed.
- PNH produces complement-mediated intravascular hemolysis and may be associated with thrombosis.
- Warm immune hemolysis is mainly IgG-mediated; cold immune hemolysis is mainly complement-associated after IgM binding.
Common KMU Trap: Spherocytes occur in both hereditary spherocytosis and warm autoimmune hemolysis; the direct antiglobulin test provides the key distinction.
5. Clinical Memory Hooks
Chronic anemia + jaundice + splenomegaly + spherocytes + negative DAT
→
Hereditary spherocytosis
→
Hereditary spherocytosis
Painful episodes + sickled RBCs
→
HbS polymerization causing vaso-occlusion
→
HbS polymerization causing vaso-occlusion
Marked microcytosis + normal iron stores + target cells
→
Consider thalassemia
→
Consider thalassemia
Dark urine after oxidant stress + bite cells
→
G6PD deficiency with oxidative hemolysis
→
G6PD deficiency with oxidative hemolysis
6. Starred High-Yield Exam Points
- ⭐ Hereditary spherocytosis: membrane-protein defect → spherocytes → splenic extravascular hemolysis.
- ⭐ Sickle cell anemia: deoxygenated HbS polymerization is the central mechanism.
- ⭐ β-Thalassemia: excess unpaired α chains cause ineffective erythropoiesis and hemolysis.
- ⭐ G6PD deficiency: Heinz bodies are denatured hemoglobin; splenic removal produces bite cells.
- ⭐ PNH: PIGA mutation → loss of GPI-linked CD55/CD59 → complement-sensitive RBCs.
- ⭐ Direct antiglobulin testing is central for diagnosing immune-mediated hemolysis and separating it from hereditary spherocytosis.