Makindo Medical Notes

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)

About

• All red cells are eventually haemolysed. Half-life is usually 120 days
• The main factor in haemolytic anaemia is not haemolysis but a significant shortening of red cell half-life
• When red cell consumption exceeds the ability to replace red cells this leads to anaemia

Causes

• Membrane defect - Hereditary spherocytosis, Hereditary elliptocytosis
• Metabolic defects - G6PDH deficiency, Pyruvate kinase deficiency
• Haemoglobinopathies - Sickle cell anaemia HbSS, Thalassaemia
• Drugs - Penicillin, Quinine
• Immune - Transfusion reaction, Haemolytic disease of newborn
• Others - Microangiopathic haemolytic anaemia - TTP, HUS, DIC, PET
• Metal heart valves
• Infection - Malaria
• Paroxysmal nocturnal haemoglobinuria

Causes: Congenital and acquired

Clinical

• Pallor, fatigue, dyspnoea
• Bleeding, bruising, rashes, lymphadenopathy
• Hepatosplenomegaly, leg ulcers, jaundice

Intravascular Haemolysis

• Red cells are broken down in the circulation and so free Hb binds to albumin to form methalbuminaemia which is detectable by Schumm's test, very reduced Haptoglobin, Raised LDH, raised unconjugated bilirubin. Hb is also found in the urine as haemosiderin.
• Causes are Paroxysmal nocturnal haemoglobinuria, G6PDH deficiency, Red cell damage - prosthetic heart valves, Microangiopathic haemolytic anaemia - HUS, TTP, Disseminated intravascular coagulation, Cold autoimmune haemolytic anaemia (Cold inside!)

Extravascular Haemolysis

• Damaged or old red cells are removed outside the vascular space usually by macrophages in the spleen or elsewhere in the reticuloendothelial system
• Causes are Hereditary spherocytosis, Sickle Cell Anaemia, Thalassaemia, Warm autoimmune haemolytic anaemia, Haemolytic disease of the newborn, Other Haemoglobinopathies

Investigations

• Hb reduced
• Blood film: Reticulocytes, polychromasia, spherocytes, anisopoikilocytosis, stomatocytosis, sickle cells (HbSS), Heinz Bodies (G6PD) fragmentation, (schistocytes), helmet cells, echinocytes.
• Serum Unconjugated bilirubin: Raised
• Urinary urobilinogen: Increased
• Urinary haemoglobinuria: Increased if intravascular haemolysis
• Coomb's (DAT) test : Positive in autoimmune anaemia due to Autoimmune HA, Alloimmunogenic, Drugs
• Coomb's (DAT) test: Negative in Mechanical heart valves, MAHA, congenital haemolysis
• Reticulocyte count: Increased
• Elevated Urinary haemosiderin (implies chronic intravascular haemolysis, e.g. PNH).
• Schumm’s test (for intravascular haemolysis).
• Low/absent serum haptoglobin (bind free Hb).
• LDH: Raised with RBC breakdown
• Red cell G6PD: low in deficiency states
• Red cell Pyruvate kinase: Low in deficiency states
• Hb analysis: detects sickle cell and other haemoglobinopathies
• Warm antibodies: IgG which agglutinate at 37 C (DAT +ve)
• Cold antibodies: IgM which agglutinates at room temperature and below (DAT +ve)
• ADAMTS13 if MAHA suspected