Page 357 - Essential Haematology

Chapter 25 Bleeding disorders / 343

the surface of platelets has not proved reliable in active orally and given daily. They are used in ITP
distinguishing ITP from other causes of thrombo- (Fig. 25.5 ) and are in trial in other conditions
cytopenia. Screening tests for DIC are also useful, (e.g. post - chemotherapy, myelodysplasia, aplastic

as are tests for an underlying disease (e.g. SLE or anaemia). They may cause disturbed liver function
HIV infection). and increased bone marrow reticulin. Th eir long -
When the blood count, including platelet count term use may cause marrow fibrosis which is revers-

and blood film examination, are normal, a PFA - 100 ible by stopping the drug.
or, much less frequently, a bleeding time is used to
detect abnormal platelet function. In most patients Platelet t ransfusions
with abnormal platelet function demonstrated by
prolonged bleeding time, or the PFA - 100 test, the Transfusion of platelet concentrates is indicated in
defect is acquired and associated either with sys- the following circumstances:
temic disease (e.g. uraemia) or with aspirin therapy.
1 Thrombocytopenia or abnormal platelet function

The very rare hereditary defects of platelet function
when bleeding or before invasive procedures and
require more elaborate in vitro tests to defi ne the
where there is no alternative therapy available

specific abnormality. These include platelet aggrega-
(e.g. steroids or high dose immunoglobulin). Th e
tion studies (Fig. 25.10 ) and measurements of 9

platelet count should be above 50 × 10 /L before,

platelet nucleotide levels. If von Willebrand disease
for example, liver biopsy or lumbar puncture.
is suspected, assay of VWF and coagulation factor
2 Prophylactically in patients with platelet counts
VIII are required. 9
of less than 5 – 10 × 10 /L. If there is infection,
potential bleeding sites or coagulopathy, the
9

Thrombomimetics count should be kept above 20 × 10 /L).
These are drugs that increase platelet production by The indications for transfusion of platelet

activating the thrombopoietin receptor on meg- concentrates are discussed further on p. 410 . Th ese
akaryocytes. Two such drugs are thromboplastin indications may change with the wider use of
given subcutaneously once weekly and eltrombopag thrombomimetic drugs.

■ Vascular bleeding disorders may be (ii) increased consumption of platelets.

congenital including hereditary This may be acute or chronic autoimmune,
haemorrhagic telangiectasia and the drug - induced, caused by disseminated
Ehlers – Danlos syndrome. intravascular coagulation or thrombotic
■ Acquired vascular disorders include fragile thrombocytopenic purpura. SUMMARY

capillaries in healthy women, senile ■ Chronic autoimmune thrombocytopenia is

purpura, purpura associated with treated by immunosuppression with
infections, Henoch – Sch ö nlein syndrome, corticosteroids, rituximab, azathioprine,
scurvy and steroid therapy. ciclosporin or by splenectomy.

■ Thrombocytopenia, if severe, also causes ■ The platelet count may be raised
skin and mucous membrane bleeding. It by platelet transfusion or by the
has a wide range of causes including: thrombomimetic drugs eltrombopag or
(i) failure of platelet production from a romiplastin.
congenital cause, drugs or viral infection ■ Disorders of platelet function may be

or a general bone marrow failure; hereditary as in von Willebrand disease,
(Continued)