Microangiopathic Haemolytic anaemia

Related Subjects: |Microangiopathic Haemolytic anaemia |Haemolytic anaemia |Immune(Idiopathic) Thrombocytopenic Purpura (ITP) |Thrombotic Thrombocytopenic purpura (TTP) |Haemolytic Uraemic syndrome (HUS) |Thrombocytopenia |Disseminated Intravascular Coagulation (DIC)

🩸 Thrombotic microangiopathies (TMA) are a group of related disorders characterised by microvascular thrombosis and resulting organ dysfunction.

📘 About Microangiopathic Haemolytic Anaemia (MAHA)

• 🔬 A haemolytic anaemia caused by red cell destruction within small vessels.
• ⏳ RBC lifespan shortened (<100 days) due to mechanical damage.
• 🩻 Blood film: schistocytes (“helmet cells”) - fragmented, triangular-shaped RBCs.

🧾 Types of MAHA

• 🟣 Thrombotic Thrombocytopenic Purpura (TTP): Anaemia, thrombocytopenia, low ADAMTS13, schistocytes + neuro signs.
• 🟢 Haemolytic-Uraemic Syndrome (HUS): Often follows shiga-toxin E. coli; presents with renal failure 🚰.
• ⚠️ Disseminated Intravascular Coagulation (DIC): Widespread clotting → RBC fragmentation.
• 💉 Heparin-Induced Thrombocytopenia (HIT): 5–14 days post-heparin; thrombocytopenia + thrombosis; anti-PF4 Abs.
• 🧬 Paroxysmal Nocturnal Haemoglobinuria (PNH): Complement-mediated RBC lysis with MAHA & cytopenias.

⚙️ Aetiology

• Fibrin clots in small vessels 🕸️ → shear stress on RBCs → fragmentation & haemolysis.

🧑‍⚕️ Clinical Presentation

• Vary by condition, but common features include anaemia + thrombocytopenia.
• 🧠 Neurological symptoms: confusion, headache, seizures (esp. TTP).
• 🚰 Renal failure: haematuria, oliguria (esp. HUS).
• 🔴 Fatigue, pallor, jaundice due to haemolysis.

🔍 Differential Diagnosis

• ⚠️ DIC
• 🟢 HUS (post-E. coli or complement-mediated)
• 🦟 Malaria (parasites visible in RBCs)
• 🟣 TTP
• 📈 Malignant hypertension
• 🤰 Severe pre-eclampsia / HELLP
• ⚙️ Mechanical heart valves (shear stress)
• 🧬 Sickle cell anaemia
• 🪨 Systemic sclerosis with renal crisis

🧪 Investigations

• 📉 Hb: Anaemia + low platelets.
• 🧪 Reticulocytes: Raised (marrow response).
• 💛 Bilirubin (unconjugated): Elevated.
• ⚡ LDH: Raised (cell breakdown).
• ⬇️ Haptoglobin: Low in intravascular haemolysis.
• 🧪 DAT (Coombs): Negative (distinguishes from autoimmune haemolysis).
• 🩻 Blood film: Schistocytes + polychromasia.
• 🟤 Urinary haemosiderin: Chronic intravascular haemolysis.
• 🧾 Clotting screen: Usually normal, except prolonged in DIC.
• 🔬 Flow cytometry: Absent CD55/CD59 in PNH.

💊 Management

• 🎯 Treat the cause: Management depends on subtype.
• 🔄 Plasma exchange: Mainstay in TTP (removes anti-ADAMTS13 antibodies).
• 💉 Plasma infusion: To replace ADAMTS13 in selected cases.
• 🩸 Supportive care: Transfusions for severe anaemia, renal support for AKI, antibiotics if sepsis.

📚 References

• Diagnostic Approach to Microangiopathic Haemolytic Disorders

Cases - Microangiopathic Haemolytic Anaemia (MAHA)

• Case 1 - Thrombotic Thrombocytopenic Purpura (TTP) ⚡: A 35-year-old woman presents with fever, confusion, and petechiae. Exam: jaundice and mild neurological deficits. Bloods: Hb 7.5 g/dL, platelets 25 × 10⁹/L, LDH ↑, haptoglobin ↓. Blood film: schistocytes. Renal function: creatinine 150 µmol/L. Diagnosis: MAHA due to TTP. Managed with urgent plasma exchange and steroids.
• Case 2 - Haemolytic Uraemic Syndrome (HUS) 🧒: A 6-year-old boy develops pallor, haematuria, and oliguria one week after bloody diarrhoea from E. coli O157 infection. Bloods: Hb 6.9 g/dL, platelets 30 × 10⁹/L, creatinine 280 µmol/L. Blood film: fragmented RBCs. Diagnosis: MAHA due to typical HUS. Managed with supportive care and dialysis if needed.
• Case 3 - Disseminated Intravascular Coagulation (DIC) 🩸: A 58-year-old man in septic shock from pneumonia develops bruising and oozing from venepuncture sites. Bloods: Hb 8.2 g/dL, platelets 40 × 10⁹/L, PT and aPTT prolonged, fibrinogen low, D-dimer ↑. Blood film: schistocytes. Diagnosis: MAHA due to sepsis-associated DIC. Managed with treatment of sepsis, blood product support, and correction of coagulopathy.

Teaching Point 🩺: MAHA is defined by intravascular RBC fragmentation (schistocytes on film) due to endothelial injury and microthrombi. Key causes: TTP (ADAMTS13 deficiency), HUS (post-E. coli diarrhoea), and DIC (sepsis, trauma, malignancy). Always think: anaemia + thrombocytopenia + red cell fragments = MAHA.