Near-haploidy in childhood leukemia: a high-risk component.

We present a 4-year-old girl with acute lymphocytic leukemia (ALL) and only 25 chromosomes at cytogenetic examination of her bone marrow. Severe hypodiploidy is extremely rare in childhood leukemia and is almost exclusively associated with ALL. To our knowledge only six cases with banded metaphases have been published. The chromosome number in the present case is the lowest ever reported. Our patient as well as other reported cases have disomy for chromosome 21. The prognosis for ALL with hypodiploidy is poor with a reported mean survival of 9 months. All published patients are females.