ANSWER 17
This woman has spontaneous bruising due to idiopathic thrombocytopenic purpura (ITP).
She has profound thrombocytopenia with a platelet count of 4% 109 /L. An increased ten-
dency to bleed or bruise can be due either to platelet, coagulation or blood vessel abnor-
malities. Platelet/vessel wall defects cause spontaneous purpura in the skin and mucous
membranes or immediately after trauma. Coagulation defects cause haematomas and
haemarthroses usually with a time delay after trauma. A positive family history or early
onset of bleeding suggests haemophilia. The distribution of bruising may suggest the
diagnosis. Thrombocytopenic purpura is most evident over the ankles and pressure areas.
Retinal haemorrhages tend to occur if there is a combination of severe thrombocytopenia
and anaemia. Senile purpura and steroid-induced bruising occur mainly on the forearms
and backs of the hands. Henoch–Schönlein purpura typically occurs over the extensor
aspects of the limbs and buttocks. Scurvy causes bleeding from the gums and around the
hair follicles. Non-accidental injury in children can present with bruising.
ITP usually occurs in young and middle-aged women. In addition to the purpuric lesions
in the skin there may be menorrhagia, epistaxes or occult or overt gastrointestinal haem-
orrhage. In this woman’s case there is a mild normochromic normocytic anaemia due to
recent blood loss. Splenomegaly is usually absent.
The causes of thrombocytopenia can be divided into disorders of reduced production of
platelets or decreased survival of platelets. Decreased production of platelets can be due to
marrow infiltration, for example by leukaemia or malignancy, or as a result of toxins, for
example alcohol, drugs (e.g. chemotherapy), radiation or viruses (e.g. cytomegalovirus [CMV]).
Platelet survival is reduced in ITP due to antibodies directed against the platelets. Secondary
causes of ITP include systemic lupus erythematosus (SLE), lymphoma, drugs such as quinine,
heparin and alpha-methyldopa and hypersplenism. Platelet consumption is increased in dis-
seminated intravascular coagulation and thrombotic thrombocytopenic purpura (TTP).
The patient should be immediately referred to a haematology unit. Platelet transfusion is usu-
ally given if there is significant bleeding or the platelet count is less than 15% 109 /L to pre-
vent a major spontaneous bleed. Investigations include assaying for platelet-associated
immunoglobulin G (IgG), excluding other causes of thrombocytopenia such as SLE and per-
forming a bone marrow aspirate. In this case it will show increased numbers of megakary-
ocytes consistent with increased platelet turnover. The platelet count in ITP normally will rise
rapidly after commencement of either corticosteroids or intravenous immunoglobulin. The
disease often runs a remitting and relapsing course. Splenectomy may be necessary.
- The distribution of purpura can aid the diagnosis.
- A family history, early onset or a history of haemarthroses suggest a diagnosis of
haemophilia. - In severe cases of ITP, urgent treatment is necessary to prevent a life-threatening
haemorrhage.