44. Karyotype and cytogenomic analysis essential in interpreting Xp-ter trisomy in a female infant with multiple anomalies

      A late preterm female infant presented to the NICU with IUGR, hypoglycemia, hypotonia, a VSD, poor postnatal growth, feeding intolerance, and dysmorphic craniofacial features. Microarray analysis identified a 23.7 Mb duplication of the Xp22.33p22.11 region. The karyotype was found to be 46,XX, der(11)t(X;11)(p22.1p15.5)dn. Telomere-associated repeat FISH confirmed that both the 11p and Xp telomere regions were intact on the p arm of the derivative chromosome as well as on the normal chromosome 11 and both normal X chromosomes. Generally, tandem duplication of small portions of the X chromosome in females will have little or no phenotypic impact due to preferential inactivation of the abnormal X. Genes in the pseudoautosomal region (PAR1), however, escape inactivation. In our patient, the 26 known genes (including SHOX, CRLF2, etc.) located in the 2.7 Mb PAR1 region will be functionally trisomic and the remaining 77 genes distal to PAR 1 functionally disomic.
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