Autoimmune haemolytic anaemia
Description
- Antibody-mediated red cell destruction with a positive direct antiglobulin test (DAT)
- *The whole classification hangs on the thermal amplitude of the antibody*
| Warm (~75%) | Cold agglutinin disease (~15%) | Paroxysmal cold haemoglobinuria | |
|---|---|---|---|
| Antibody | IgG (+/- C3d) | IgM | IgG (Donath-Landsteiner), biphasic |
| Optimal temperature | 37 C | 4 C (thermal amplitude up to ~30 C matters) | Binds cold, lyses at 37 C |
| Target antigen | Rh complex | I / i | P antigen |
| DAT pattern | IgG +/- C3d | *C3d only* | C3d only |
| Site of destruction | Extravascular - spleen | Extravascular - liver (Kupffer cells) + intravascular | Intravascular |
| Film | Spherocytes | Agglutination, rouleaux-like clumping | Spherocytes, erythrophagocytosis |
| Treatment | Corticosteroid | *Keep warm + rituximab. Steroids do NOT work* | Warmth, supportive |
- Mixed (warm + cold) AIHA - both antibodies; usually severe
- *Splenomegaly is common in warm AIHA and unusual in cold agglutinin disease*
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