Dysplastic changes in the peripheral blood of children with microdeletion 22q11.2.

Myelodysplasia refers to abnormal morphology of the bone marrow and/or peripheral blood. This condition is frequently due to myelodysplastic syndrome; however, myelodysplasia is caused by a variety of factors and is not always a sign of pre-malignant disease. We observed myelodysplastic changes in peripheral blood smears and bone marrow specimens from a patient who had chromosomal microdeletion 22q11.2 (del22q11.2). We then investigated such changes in several other patients who were newly diagnosed with del22q11.2 (n = 5 total, including the index case) and compared the findings to those in four sets of controls without this chromosomal abnormality. Specifically, the controls were children with conotruncal heart defects (n = 3); otherwise healthy children with bacterial (n = 4) or viral infection (n = 4); and healthy children (n = 4). The myelodysplasia scores in the myeloid cells and eosinophils of the children with del22q11 were higher than those in all four of the control groups. Myelodysplastic changes in the peripheral blood of children with del22q11.2 have not been reported previously. We believe that certain gene(s) in the deleted region may be responsible for the myelodysplastic changes that we observed in our patients with this chromosomal abnormality.