Page 351 - Essential Haematology

Chapter 25 Bleeding disorders / 337

Eltrombopag 50 mg daily Post-therapy
240
200
Platelet count (x 10 9 /L) 160

120

80
40
0
1 10 23 38 66 108 178 213 234
Study day

Figure 25.5 Response to eltrombopag in chronic immune thrombocytopenic purpura in a female aged 75 after

failure of response to prednisolone. (Courtesy of Professor A. Newland.)
The diagnosis is one of exclusion and there is bocytopenias (Fig. 25.6 ). Quinine (including that

debate as to the need for bone marrow aspiration. in tonic water), quinidine and heparin are particu-
9
If the platelet count is over 30 × 10 /L no treatment larly common causes (Table 25.3 ).
9

is necessary unless the bleeding is severe. Th ose with The platelet count is often less than 10 × 10 /L,
9

counts below 20 × 10 /L may be treated with ster- and the bone marrow shows normal or increased
oids and/or intravenous immunoglobulin, espe- numbers of megakaryocytes. Drug - dependent anti-

cially if there is significant bleeding. bodies against platelets may be demonstrated in the

sera of some patients. The immediate treatment is
Infections to stop all suspected drugs but platelet concentrates
should be given to patients with dangerous
It seems likely that the thrombocytopenia associated bleeding.
with many viral and protozoal infections is immune -
mediated. In HIV infection, reduced platelet pro-
duction is also involved (see p. 390) . Thrombotic t hrombocytopenic p urpura
and h aemolytic u raemic s yndrome
Post - t ransfusion p urpura Thrombotic thrombocytopenic purpura (TTP)

Thrombocytopenia occurring approximately 10 occurs in familial or acquired forms. There is defi -
days after a blood transfusion has been attributed ciency of the ADAMTS13 metalloprotease which
to antibodies in the recipient developing against the breaks down ultra large von Willebrand factor mul-
human platelet antigen - 1a (HPA - 1a) (absent from timers (ULVWF) (Fig. 25.7 ). In the familial forms
the patient s own platelets) on transfused platelets. more than 50 ADAMTS13 mutations have been
’
’
The reason why the patient s own platelets are reported whereas the acquired forms follow the

then destroyed is unknown. Treatment is with development of an inhibitory IgG autoantibody,
intravenous immunoglobulin, plasma exchange or the presence of which may be stimulated by infec-
corticosteroids. tion, autoimmune/connective tissue disease, certain
drugs, stem cell transplantation or cardiac surgery.
ULVWF multimeric strings secreted from Weibel –
Drug - i nduced i mmune t hrombocytopenia

Palade bodies are anchored to the endothelial cells,
An immunological mechanism has been demon- and passing platelets adhere via their GPIb
strated as the cause of many drug - induced throm- receptors. Increasing platelet aggregation onto the