Page 100 - Essential Haematology

86 / Chapter 6 Haemolytic anaemias

Figure 6.11 Blood fi lm in
microangiopathic haemolytic
anaemia (in this patient, Gram -
negative septicaemia). Numerous
contracted and deeply staining
cells and cell fragments are
present.

pneumococcal septicaemia). Malaria causes haemo-
Protein,
lysis by extravascular destruction of parasitized e.g. CD59, CD55
red cells as well as by direct intravascular lysis.
Blackwater fever is an acute intravascular haemoly-
sis accompanied by acute renal failure caused by Glycan Glycan core
Falciparum malaria. Clostridium perfringens septi-
caemia can cause intravascular haemolysis with
marked microspherocytosis.
Phosphatidyl Inositol

Chemical and p hysical a gents
®
Certain drugs (e.g. dapsone and Salazopyrin ) in
high doses cause oxidative intravascular haemolysis
with Heinz body formation in normal subjects. In
’
Wilson s disease an acute haemolytic anaemia can
occur as a result of high levels of copper in the
blood. Chemical poisoning (e.g. with lead, chlorate Figure 6.12 Schematic representation of the phos-

or arsine) can cause severe haemolysis. Severe phatidylinositol glycan which anchors many different
burns damage red cells causing acanthocytosis or proteins to the cell membrane (e.g. CD59).
spherocytosis.
glycosylphosphatidylinositol (GPI) anchor, a struc-
Secondary h aemolytic a naemias
ture that attaches several surface proteins to the cell
In many systemic disorders red cell survival is short- membrane. It results from acquired mutations in

ened. This may contribute to anaemia (see Chapter the X chromosome gene coding for phosphatidyl-
28 ). inositol glycan protein class A (PIG - A) which is
essential for the formation of the GPI anchor. Th e
net result is that GPI - linked proteins (such as CD55
Paroxysmal n octurnal h aemoglobinuria
and CD59) are absent from the cell surface of all
PNH is a rare acquired clonal disorder of marrow the cells derived from the abnormal stem cell (Fig.

stem cells in which there is deficient synthesis of the 6.12 ). Th e lack of surface molecules decay - activating