Differential diagnosis of ITP

What are the key steps in the differential diagnosis of immune thrombocytopenia (ITP)?

Bertrand Godeau, MD, PhD: Three situations. The first one, as I mentioned [see: Signs and symptoms suspicious for ITP], is CVID, common variable immunodeficiency disease. It is clear that if you have patients who are 20 or 30 years old, you must be aware that ITP can be associated with CVID and that ITP can precede CVID. So it is necessary to check the gamma globulin level.

The second differential diagnosis when a patient is elderly or >60 years old is myelodysplastic syndrome (MDS). It is clear that it is sometimes difficult to differentiate between MDS and ITP, and mostly some MDS cases can be associated with autoimmune cytopenia. Our practice in a lot of European countries is to systematically perform bone marrow aspiration after the age of 60 in order to rule out the diagnosis of MDS.

The third diagnosis is congenital thrombocytopenia. It is sometimes difficult. The message is, if you have a patient with thrombocytopenia, you must check the previous platelet count, because if they had a normal platelet count 10 or 20 years ago, you are sure that it is not congenital thrombocytopenia. But if you have no previous platelet count, it is important to check the patient, to see the response to first-line treatment, and if you have no response to steroids, if you have no response to intravenous immunoglobulin (IVIG), it is necessary to check the platelet count in the family and to see the platelet volume in giant platelets or [small] platelets. If you have giant platelets or micro platelets, it is an indication of potential congenital thrombocytopenia, familial thrombocytopenia.

Sure, you must avoid thrombocytopenia associated with drugs, but it is clear that the first step is to test the drugs taken by the patients in the weeks preceding the diagnosis of thrombocytopenia.