Thrombocytopenia and immune thrombocytopenia: Case

This girl has the classic presentation of newly diagnosed immune thrombocytopenia, ITP. She is a well preschool child, two weeks after a viral illness, with the sudden bruising and the petechiae, the isolated thrombocytopenia at 8 times ten to the nine per litre, the normal haemoglobin and white cell count, the large platelets and the absence of blasts on the film, and the absence of the organomegaly. The small nosebleed that stopped with pressure is the mild mucosal bleeding, and it places her at the boundary of the mild and the moderate bleeding grade. ^[1][4]

Interpretation of the findings

The key findings are the isolated thrombocytopenia, the normal blood film, and the well child. The platelet count of 8 times ten to the nine per litre is well under the threshold of 100 times ten to the nine per litre, and it is the only abnormality on the full blood count. The blood film shows the large platelets, which is the expected finding in ITP because the young platelets are larger, and the absence of the blast cells, the schistocytes, and the other abnormalities that would point to the acute leukaemia, the haemolytic uraemic syndrome, or another alternative diagnosis. The normal haemoglobin and white cell count exclude the marrow infiltration, and the absence of the hepatosplenomegaly and the lymphadenopathy exclude the leukaemia and the infiltrative disorders at the bedside. ^[4]

The diagnosis of ITP is therefore made on the combination of the isolated thrombocytopenia, the normal film, the well child, and the absence of the organomegaly, and it is a clinical diagnosis made by exclusion. A bone marrow aspirate is not indicated, because the ASH 2019 guideline recommends against the routine marrow aspirate in the child with the typical presentation. The marrow is reserved for the atypical case, the case with the other cytopenias, the blasts, or the organomegaly. ^[1]