Immune Mediated Thrombocytopenia (ITP)

The key finding in this film is the absolute thrombocytopenia with the absence of clumping or satellitism. Platelets are infrequent with only a handful visible on the film. Those platelets which are seen are enlarged and the patient has both a raised MPV and reticulated platelet count. This is characteristic of immune thrombocytopenia. Other causes of macrothrombocytopenia (such as the MYH9-opathies) do not cause such a profound thrombocytopenia.

Although many haematological disorders can cause a severe thrombocytopenia, these are universally associated with white cell or red cell changes. In this case, both the white cells and red cells appear completely normal. One critical red cell finding not to miss in patients with severe thrombocytopenia is iron deficiency, There is no evidence of that here and this is a significant negative to note.

Lymphocytes in this film are normal, although frequently there is an increase in reactive lymphocytes or large granular lymphocytes. Remember that ITP (especially in children) is associated with viral infections and as such there may be ongoing evidence of a recent illness.

Don't forget in such cases to comment that one should get a repeat sample - with normal white cell and red cell morphology, a clot in the tube could equally give you such an absolute thrombocytopenia and of course this would be of much less worrying for the patient.