Markers of intravascular haemolysis
Core concept
- Intravascular = red cells lysed in the circulation -> free Hb spills into plasma
- Haptoglobin binds free Hb -> cleared by CD163 macrophages -> haptoglobin is consumed
- Once haptoglobin is saturated: haemoglobinaemia -> haemoglobinuria -> haemosiderinuria (days later, from tubular cell shedding)
- Free Hb scavenges nitric oxide -> the clinical syndrome of dystonia, abdominal pain, pulmonary hypertension, priapism, thrombosis
- Extravascular = phagocytosis in spleen and liver -> no free plasma Hb
- -> splenomegaly, marked unconjugated hyperbilirubinaemia, pigment gallstones; haptoglobin only mildly low
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