Bleeding child: diagnostic approach: Case

Case discussion

Diagnosis and immediate assessment

This boy presents the classic picture of acute immune thrombocytopenia: sudden petechiae and bruising in an afebrile, otherwise well preschool child, one to two weeks after a viral illness, with isolated severe thrombocytopenia and a normal prothrombin and activated partial thromboplastin time. The bleeding pattern is primary-hemostasis (platelet-type): immediate, mucocutaneous, and petechial. The first step is to confirm the diagnosis and exclude its dangerous mimic, acute lymphoblastic leukaemia, before any treatment that could mask it. ^[1]

Excluding leukaemia before treatment

The blood film is the single most important test here. The absence of blast cells, the normal haemoglobin and white cell count, the absence of additional cytopenias, and the well appearance all support immune thrombocytopenia over leukaemia. Large platelets on the film reflect young, reactive platelets, consistent with peripheral destruction rather than marrow failure. Before any corticosteroid is given, the film must be reviewed, because treating leukaemia with steroids can mask the diagnosis and delay definitive chemotherapy. The absence of hepatosplenomegaly and lymphadenopathy further supports the benign diagnosis. ^[3]

Pathophysiology

Immune thrombocytopenia is an antibody-mediated destruction of platelets, often triggered by a recent viral infection that generates antibodies that cross-react with platelet surface glycoproteins. The platelets are opsonised and cleared by splenic macrophages, producing isolated severe thrombocytopenia. The bone marrow is normal or shows increased megakaryocytes, which is why the film shows large, young platelets. The bleeding pattern is purely primary-hemostasis, because the coagulation factors are intact, which is why the prothrombin and activated partial thromboplastin times are normal. ^[1]