A clinical study is performed in which the subjects are children 1 to 4 years old who have had multiple infections with viral, fungal, and parasitic diseases. Compared with a normal control group, these children do not have thymic cells that bear markers of cortical lymphocytes. Which of the following karyotypic abnormalities is most likely to be seen in the children in this study?
These cells mark as cortical lymphocytes in the thymus of a child. An absence of such cells can be seen in DiGeorge syndrome with 22q11.2. Such patients also can have parathyroid hypoplasia and congenital heart disease. Patients with Down syndrome (trisomy 21) can have thymic abnormalities and the T-cell dysregulation that predisposes to acute leukemia, but the thymus is typically present. The t (9;22) gives rise to the Philadelphia chromosome, which is characteristic of chronic myelogenous leukemia. The t (15;17) is seen in patients with acute promyelocytic leukemia. Individuals with fragile X syndrome usually have some form of mental retardation. Males with Klinefelter syndrome (XXY) do not have immunologic abnormalities.
21
22q11.2
t (9;22)
t (15;17)
Blood