A 70-year-old man has an annual check up with his doctor. He has no symptoms. The blood count shows a platelet count of 55 × 109/L.
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(a) What clinical features are you going to look for on examination?
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Correct answer:
Evidence of bruising or bleeding. Whether his liver or spleen is enlarged. Any cause of an enlarged spleen could cause thrombocytopenia. Whether he is anaemic (pallor of mucous membranes).
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(b) What further information would you wish to know from his blood count?
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Correct answer:
It is important to know whether the rest of his blood count is normal or not. Particularly whether he is anaemic or has a raised MCV or low neutrophil count, all features of megaloblastic anaemia or myelodysplasia which are frequent at his age. Also whether the lymphocyte count is raised suggesting chronic lymphocytic leukaemia, also common at this age.
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(c) What further clinical history do you wish to obtain?
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Correct answer:
It is important to know if he is taking any drugs that might cause a low platelet count. Diuretics, oral hypoglycaemic agents, analgesics, anticonvulsants and other drugs can cause thrombocytopenia.
Also his post medical history is important. Whether he has had a low platelet count or easy bruising or bleeding in the past. Immune thrombocytopenia (ITP) tends to recur throughout life.
It is also important on direct questioning to establish whether or not he is bruising or bleeding easily.
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(c) What further tests do you request?
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Correct answer:
(a) Examination of the blood film for features of myelodysplasia such as hypogranular neutrophils, Pelger-like neutrophils or of megaloblastic anaemia (oval macrocytes hypersegmented neutrophils).
(b) Bone marrow examination with cytogenetic analysis is needed. This will diagnose myelodysplasia. In ITP, the marrow will be normal or show increased megakaryocytes.
(c) Tests for antinuclear antibodies and double stranded DNA antibodies. These are to exclude SLE, unlikely at his age, but a known cause of thrombocytopenia.
(d) Coagulation tests – prothrombin time (PT), and activated partial thrombophilia time (APTT) to exclude low grade disseminated intravascular coagulation.
(e) Liver function tests – liver disease with portal hypertension and splenomegaly can cause an isolated thrombocytopenia.
