A case of down syndrome with acute lymphoblastic leukemia and isochromosome Xp

A 3-year, 9-month-old girl with trisomy 21 was diagnosed with acute lymphoblastic leukemia (ALL). The karyotype of her leukemic cells at diagnosis—48,XX,+i(X)(p10),+21c—included an extra, structurally abnormal X chromosome as the sole acquired abnormality. While an extra X chromosome is a common abnormality in childhood ALL, it is seldom the only acquired aberration. Furthermore, an additional X chromosome that is structurally abnormal is rare, and has not been reported previously as a solitary abnormality. Here we report a novel karyotype in childhood ALL and review the eight previously described cases of ALL with an extra X isochromosome as the only acquired abnormality.