Duplication of isodicentric chromosome 21, idic(21)(p11.2), leading to pentasomy 21q in acute myeloid leukemia with multilineage dysplasia

Acute multilineage (B/myeloid) leukemia with RUNX1 duplication/amplification and hypereosinophilia

A 14-year-old girl presented with myalgias and decreased energy and was found to have a white count of 73,000 with 75% eosinophils. Flow cytometry and immunostains showed the blasts in the bone marrow expressed both myeloid and lymphoid markers. Patient was diagnosed with acute multilineage (B/Myeloid) leukemia. Genetic testing revealed four copies of the RUNX1 gene region in 25.5%, with a normal karyotype and no evidence of t(8;21) or t(12;21) by fluorescence in situ hybridization. RUNX1 translocations and amplifications have been implicated in acute myeloblastic leukemia, acute lymphoblastic leukemia, and MDS, but have not yet been seen with acute multilineage leukemia. Additionally, it is unclear what the risk stratification of this unique presentation will turn out to be.

Duplication of isodicentric chromosome 13, idic(13)(p11.2), leading to pentasomy 13q in acute myeloid leukemia without maturation

Isodicentric chromosome 13, idic(13)(p11.2), is a very rare chromosomal aberration in acute myeloid leukemia (AML). We describe here a novel case of AML without maturation, where the leukemic cells harbored double idic(13)(p11.2) and a normal chromosome 13 resulting in pentasomy 13q. Analyses were done on aspirated bone marrow cells from diagnosis. We utilized G-banding analysis, 24-color karyotyping and additional FISH analyses with various locus-specific probes to characterize the chromosomal complement. Oligonucleotide-based 180K aCGH analysis was done to search for submicroscopic imbalances. The karyotype was 47,XY,idic(13)(p11.2)x2[23]/46,XY[2]. Pantelomeric FISH analysis indicated critically short telomeres. Oligo-based aCGH analysis confirmed high copy gain of chromosome 13q and did not disclose other genomic imbalances. Reviewing the literature, this may be the second case of pentasomy 13q, since idic(13)(p11.2), when analyzed by conventional cytogenetics, is indistinguishable from i(13)(q10). Both cases were associated with immature AML and a poor outcome. We propose that idic(13)(p11.2) is a new recurrent abnormality in AML without maturation and suggest that pentasomy 13q is an early event in pathogenesis of AML through amplification of genes located on 13q.