Page 99 - Essential Haematology

Chapter 6 Haemolytic anaemias / 85

Penicillin Quinidine Methyldopa

C

Drug Plasma protein C Complement Antibody

Figure 6.10 Three different mechanisms of drug - induced immune haemolytic anaemia. In each case the coated

(opsonized) cells are destroyed in the reticuloendothelial system.
1 Antibody directed against a drug – red cell mem-

Table 6.6 Red cell fragmentation syndromes.
brane complex (e.g. penicillin, ampicillin). Th is
only occurs with massive doses of the antibiotic. Cardiac haemolysis Prosthetic heart valves
2 Deposition of complement via a drug – protein Patches, grafts
(antigen) – antibody complex onto the red cell Perivalvular leaks
surface (e.g. quinidine, rifampicin); or
Arteriovenous

3 A true autoimmune haemolytic anaemia in

malformations
which the role of the drug is unclear (e.g.
methyldopa). Microangiopathic TTP - HUS
Disseminated
In each case, the haemolytic anaemia gradually intravascular
disappears when the drug is discontinued. coagulation
Malignant disease
Vasculitis (e.g.
Red c ell f ragmentation s yndromes
polyarteritis nodosa)

These arise through physical damage to red cells Malignant hypertension
either on abnormal surfaces (e.g. artifi cial heart Pre - eclampsia/HELLP
valves or arterial grafts), arteriovenous malforma- Renal vascular disorders/
tions or as a microangiopathic haemolytic anaemia. HELLP syndrome

This is caused by red cells passing through abnormal Ciclosporin
small vessels. The latter may be caused by deposition Homograft rejection

of fibrin strands often associated with disseminated
intravascular coagulation (DIC) or platelet adher- HELLP, haemolysis with elevated liver function tests and
low platelets; HUS, haemolytic uraemic syndrome; TTP,
ence as in thrombotic thrombocytopenic purpura thrombotic thrombocytopenic purpura.

(TTP) (see p. 337) or vasculitis (e.g. polyarteritis

nodosa; Table 6.6 ). The peripheral blood contains

many deeply staining, red cell fragments (Fig. 6.11 ). marching or running. The blood film does not show

When DIC underlies the haemolysis, clotting abnor- fragments.
malities (see p. 335) and a low platelet count are also
present. TTP is discussed in detail on page 337 .
Infections
Infections can cause haemolysis in a variety of ways.
March h aemoglobinuria

They may precipitate an acute haemolytic crisis

This is caused by damage to red cells between the in G6PD deficiency or cause microangiopathic

small bones of the feet, usually during prolonged haemolytic anaemia (e.g. with meningococcal or