22nd July 2024

Overview of haemolytic anaemia

This is anaemia secondary to premature destruction of RBCs. It can range in severity and be acute or chronic. There are various underlying causes, but useful distinctions include whether or not the process is immune-system driven and whether it occurs in intra- or extravascular space(s), the latter including the spleen, liver and bone marrow. If haemolysis is not compensated for by increased RBC production, then it is likely to cause symptomatic anaemia with fatigue and jaundice.

Results indicating a haemolytic process include raised reticulocytes, low haptoglobin (this binds to free haem released from lysed RBCs), raised LDH (lactate dehydrogenase) and raised unconjugated bilirubin.

Intravascular haemolysis is suggested by positive urinary tests:

• Haemoglobinuria: free haemoglobin rather than whole RBCs
• Haemosiderinuria: free haemoglobin which has been filtered and stored as haemosiderin in the renal tubules is then excreted in the urine; this can stay positive for ~1 week

Splenomegaly is associated with extravascular haemolysis, and patients may have a history of recurrent pigment gallstones due to excess unconjugated bilirubin.