Early diagnosis of leukemia in a child with Down syndrome
A 4-year-old child with Down syndrome came to the Albert Schweitzer Hospital in Dordrecht for a routine check-up with his pediatrician. In our lab, blood cell counts showed a normal hemoglobin level (7.4 mmol/L; 11.9 g/dL), mild thrombo-cytopenia (platelet count 98 x 109/L) and a normal leukocyte count. Morphological analysis of the peripheral blood smear using a digital analyzer (CellaVision DM96) indicated the presence of 2% blasts and 1% erythroblasts (nucleated red blood cells). As these results were highly suggestive of leukemia, we transferred the patient to a nearby academic hospital for further investigation.Image of blasts captured on a CellaVision DM96
Further analysis and diagnosis
Our colleagues at a nearby academic hospital took a bone marrow
sample and a further peripheral blood sample from the patient to conduct flowcytometry in order to identify the blast phenotype. The blasts were positive for the B cell lineage markers CD19, CD10, CD20, CD22 and CD79 (cytoplasmic), weakly positive for the hematolymphoid marker CD45 and positive for the lymphoid precursor marker terminal deoxynucleotidyltransferase (TdT). The blasts were negative for cytoplasmic immunoglobulin M and also negative for neuron glial antigen 2 (NG2), a marker associated with rearrangement of MLL gene in some acute leukemias. Both the morphological and immuno-logical findings indicated that the child had acute B lymphoblastic leukemia (B-ALL; common ALL).
Children with Down syndrome have a 10–20 fold increased risk of both myeloid and lymphoid leukemias. This case illustrates that early detection of blast cells using digital morphology is an essential component of the diagnostic process for leukemia and enables earlier treatment of these patients.
Thanks to Rob Castel and Jürgen Riedl, GKCL, Albert Schweitzer Hospital, Dordrecht, The Netherlands, for sharing this interesting case.
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