Red cells and bleeding disorders

Anaemias, polycythaemia, platelet and clotting disorders, and transfusion.

25 pages

Mechanism

• Acquired coagulation factor disordersMost clotting factor problems are acquired: too little vitamin K, a failing liver, antibodies…
• Anaemia of chronic inflammation: IL-6, hepcidin and locked-away ironIn long infections, autoimmune disease or cancer, the body hides iron from microbes
• Haemolysis: extravascular vs intravascularRed cells that die early are eaten by macrophages or burst inside vessels
• Thrombocytopenia: mechanismsA low platelet count comes from poor production, quick destruction, trapping in a big spleen or…

Topic

• Anaemia: classificationAnaemia is too little red cell mass
• Bleeding disorders: overviewBleeding comes from weak vessels, too few or faulty platelets, or missing clotting factors
• Complications of transfusionTransfusion is safe but not risk-free: fever, allergy, destroyed donor cells, lung injury, fluid…
• Red cell morphology on the smearRed cell shapes and inclusions are clues: each abnormal form points to a small set of diseases

Lesion

• Aplastic anaemiaThe marrow empties of blood-forming cells and fills with fat
• G6PD deficiency: oxidant haemolysis, Heinz bodies and bite cellsRed cells cannot defend against oxidants
• Haemophilia A and BBoys born without enough factor VIII or IX bleed deep into joints and muscles
• Hereditary spherocytosisAn inherited weakness of the red cell skeleton makes cells lose membrane and become spheres that…
• Immune thrombocytopenias: ITP and HITAntibodies coat platelets so the spleen removes them
• Immunohaemolytic anaemiaAntibodies stick to red cells and mark them for destruction
• Iron deficiency anaemiaThe commonest anaemia in the world: iron stores empty first, then cells become small and pale
• Megaloblastic anaemias: B12 and folateWithout vitamin B12 or folate, cells cannot copy DNA
• Other marrow failure: PRCA and myelophthisisSometimes only red cells stop being made, sometimes tumour fills the marrow, and sometimes…
• Paroxysmal nocturnal haemoglobinuriaAn acquired stem cell mutation removes the shields that protect blood cells from complement
• Platelet function disordersPlatelets can be present in normal numbers but fail to stick, clump or release their signals
• Sickle cell diseaseOne amino acid change makes haemoglobin stack into rods when oxygen is low
• Thalassaemias: β and αToo few globin chains of one kind: cells are small and pale, the unpaired chains clump and kill…
• Thrombotic microangiopathies: TTP vs HUSPlatelet clots plug small vessels, cut red cells and starve organs
• Traumatic haemolysisRed cells can be cut by abnormal valves, fibrin strands in small vessels or repeated blows to…
• Vascular bleeding disordersWhen the small vessels themselves are weak, the skin and mucosa bleed even though platelets and…
• Von Willebrand diseaseThe commonest inherited bleeding disorder: too little or faulty von Willebrand factor, so…

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← General pathology

Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.

Representative model, for educational purposes only.