A Novel Variant Rearrangement of the Rare Aberration dic(17;20)(p11.2;q11.2) Characterized by Array-CGH as an Insertion in a Patient with Myelodysplastic Syndrome of Multilineage Dysplasia (MDS-MLD)

We report on a novel variant of the dicentric chromosome 17;20 (dic (17;20)(p11.2;q11.2) in a patient with de novo myelodysplastic syndrome (MDS). Based on FISH and array-CGH, the variant turns out to be an insertion of chromosome 17 (17p11.2-telomere 17) into chromosome 20 with breakpoints at 20q11.22 and 20q13.33. Based on conventional chromosome analysis and G-banding patterns, the region 17p11.2-17q25 was directly inserted between 20q11.22 and 20q13.33. The breakpoint junctions occurred within <i>KCNJ12</i> (17p11.2), <i>UQCC1</i> (20q11.2), and <i>CDH4</i> (20q13.3), leading to 5′ deletions of all the genes and positioning the 3′ of <i>UQCC1</i> next to <i>KCNJ12</i> at 17p11.2 and <i>CDH4 </i>next to an unknown gene at 17q25-20q13.3<i>.</i> In addition, the centromere of chromosome 17 was not active, transforming the primary constriction to a flat band. Therefore, the novel insertion variant is a pseudo dicentric derivative chromosome with one functional centromere: 45,XX,der(17;20)del(20)(q11.22q13.33)ins(20;17)(q11.2;p11.2q25). A review of the literature of all dic(17;20) cases is presented. For the first time, we report an array-CGH characterization of such rare variant that revealed to be an insertion.