Page 348 - Essential Haematology

334 / Chapter 25 Bleeding disorders

Table 25.2 Causes of thrombocytopenia. Table 25.3 Thrombocytopenia as a result of

drugs or toxins.
Failure of platelet production
Selective megakaryocyte depression Bone marrow suppression
rare congenital defects (see text) Predictable (dose - related)
drugs, chemicals, viral infections ionizing radiation, cytotoxic drugs, ethanol
Part of general bone marrow failure Occasional
cytotoxic drugs chloramphenicol, co - trimoxazole, idoxuridine,
radiotherapy penicillamine, organic arsenicals, benzene, etc.
aplastic anaemia
Immune mechanisms (proven or probable)
leukaemia
Analgesics, anti - infl ammatory drugs
myelodysplastic syndromes
gold salts
myelofi brosis
Antimicrobials
marrow infi ltration (e.g. carcinoma, lymphoma, penicillins, rifamycin, sulphonamides,
Gaucher ’ s disease)
trimethoprim, para - aminosalicylate
multiple myeloma
Sedatives, anticonvulsants
megaloblastic anaemia
diazepam, sodium valproate, carbamazepine
HIV infection
Diuretics
Increased consumption of platelets acetazolamide, chlorathiazides, frusemide
Immune Antidiabetics
autoimmune chlorpropamide, tolbutamide
idiopathic Others
associated with systemic lupus erythematosus, digitoxin, heparin, methyldopa, oxyprenolol,
chronic lymphocytic leukaemia or lymphoma; quinine, quinidine
infections: Helicobacter pylori , HIV, other
viruses, malaria
drug - induced, e.g. heparin
post - transfusional purpura cal history, peripheral blood count, the blood fi lm
feto – maternal alloimmune thrombocytopenia and bone marrow examination.
Disseminated intravascular coagulation
Thrombotic thrombocytopenic purpura
Increased d estruction of p latelets
Abnormal distribution of platelets
Splenomegaly (e.g. liver disease) Autoimmune ( i diopathic)
t hrombocytopenic p urpura
Dilutional loss
Massive transfusion of stored blood to bleeding Autoimmune (idiopathic) thrombocytopenic
patients purpura (ITP) may be divided into chronic and
acute forms.
HIV, human immunodefi ciency virus.
Chronic i diopathic t hrombocytopenic
p urpura
This is a relatively common disorder. Th e highest

association with absent radii, or in May – Hegglin incidence has been considered to be in women aged
anomaly with large inclusions in granulocytes, or in 15 – 50 years although some reports suggest an
Wiskott – Aldrich syndrome (WAS) with eczema increasing incidence with age. It is the most common
and immune deficiency. WAS is caused by mutation cause of thrombocytopenia without anaemia or

of the WASP gene, the protein being a regulator of neutropenia. It is usually idiopathic but may be seen
signalling in haemopoietic cells. Diagnosis of these in association with other diseases such as systemic
causes of thrombocytopenia is made from the clini- lupus erythematosus (SLE), human immunodefi -